INTRODUCTION

TO INSECTS

Natalie Boyle

Michael Skvarla

D.J. McNeil
Department of Entomology Nate Reagle
 TABLE OF
CONTENTS

Introduction 1
Insect Structure 2
Insect Order Descriptions 7
Insect Conservation 23
Glossary 23
References 24
Photo Credits 24
INTRODUCTION
Insects are essential to the functioning of all ecosystems.
As the dominant herbivores of most terrestrial communi-
ties in Pennsylvania, insects move energy from plants up
the food chain, supporting a critical link in the food web.
Insects are a major food source for many species of fish,
amphibians, reptiles, birds, and mammals. Birds rely on
insects during the nesting season to provide their young
with adequate nutrition. This resource is so valuable that 59. Some parasitic wasps lay their eggs under the skin of insect
many bird species will migrate thousands of miles from hosts (such as this tomato hornworm), which will kill the host
the tropics to take advantage of the seasonal bounty of and naturally suppress pest populations in agricultural fields
insects in temperate regions.
Some non-native insects are unfortunately very detrimen-
When insects feed and break down both live and dead tal to native ecosystems. Some non-native insect pests in
material, they return nutrients to the soil. Thus, insects Pennsylvania include the gypsy moth, emerald ash borer,
are efficient and crucial players in nutrient cycling. hemlock woolly adelgid. These insects are extremely dam-
aging to oaks, ash, and hemlock respectively, all of which
The majority of pollinators in Pennsylvania are insects are native to Pennsylvania.
such as bees, flies, beetles, butterflies, and moths. Be-
cause many native plants require insect pollination for
reproduction, invertebrates help to perpetuate ecosys-
tems and the services they provide to human society, as
well as produce food for wildlife.

38. The Emerald Ash Borer is an invasive beetle whose larval

stage feeds on, damages, and kills native ash trees throughout
the United States and Canada

CLASSIFICATION
All life is organized using hierarchical classification,
where each larger group can be broken down into small-
er groups, somewhat similar to computer folders and
subfolders. All animals, including insects, fall into the
kingdom Animalia. Within Animalia are a number of phy-
la, including Chordata (animals with backbones, including
all fish, birds, and mammals such as humans), Mollusca
(including squid, octopods, slugs, snails, clams, etc), and
Arthropoda, which includes insects and related animals
8. Bumblebees are important pollinators of flowering plants in such as shrimp, crabs, millipedes, centipedes, and spiders.
Pennsylvania
Arthropods are characterized by having a segmented
Other insects are valuable as agents of Integrated Pest body that is groups into larger units called tagma (plural:
Management (IPM). Insect predators and parasitoids can tagmata), jointed legs, compound eyes, and a hardened
keep pest populations at low levels and reduce depen- exoskeleton. The number of tagma, legs, and eyes can vary
dency on pesticides. The pollination and pest manage- between different arthropod groups – for example, spiders
ment services provided by insects can have significantly and other arachnids have eight legs while crabs and other
positive economic and ecological impacts. decapods have ten legs.

1
Arthropods are the most diverse group of animals, with NUMBER OF
1.7–30 million species estimated to exist. Because it is COMMON
ORDER DESCRIBED
NAMES
so diverse, the phylum Arthropoda includes a number SPECIES
of subphyla, including Chelicerata (spiders, scorpions, Blattodea cockroaches, termites 7,314
mites, etc), Mandibulata (millipedes and centipedes), Coleoptera beetles 387,100
Crustacea (crustaceans such as crabs and lobsters, al- Collembola springtails 8,130
Dermaptera earwigs 1,978
though this is not a natural, or monophyletic, group), and
Diplura Diplurans 800
Hexapoda (insects, springtails, and relatives).
Diptera flies 155,477
Embioptera* webspinners 463
Hexapoda contains 2–4 classes, depending on the classifi- Ephemeroptera mayflies 3,240
cation: Insecta (insects), which includes the vast majority Hemiptera true bugs, leafhoppers, aphids 103,590
of hexapod diversity, and the non-insect hexapods Col- Hymenoptera bees, wasps, sawflies, ants 116,861
lembola (springtails), Protura (coneheads) and Diplura Lepidoptera moths and butterflies 157,338
(two-pronged bristletails), which are much less diverse. Mantodea mantids 2,400
Because they are closely related to insects, and are found Mecoptera scorpionflies 757
Megaloptera dobsonflies, alderflies 354
Microcoryphia jumping bristletails 513
Neuroptera lacewings, antlions 5,868
Historically, non-insect Hexapods were Notoptera* ice crawlers, rock crawlers 49
organized into the class Entognatha, which Odonata dragonflies, damselflies 5,899
Orthoptera grasshoppers, crickets, katydids 23,846
contained three orders: springtail (Collembola), Phasmatodea walking sticks 3,014
coneheads (Protura), and two-pronged bristle- Plecoptera stoneflies 3,743
Protura proturans, coneheads 804
tails (Diplura). Recent research has suggested
Psocodea parasitic lice, book lice, bark lice 10,822
Entognatha is not a natural group, so some Raphidioptera* snakeflies 254
Siphonaptera fleas 2,075
scientists have raised the old orders to classes
Strepsiptera twisted-wing parasites 609
(for example, class Collembola instead of order Thysanoptera thrips 5,864
Collembola), which then each contain a number Trichoptera caddisflies 14,391
Zoraptera zorapterans 37
of orders. This change is not yet fully recog- Zygentoma silverfish, firebrats 561
nized, so for easy of understanding and to be
Table 1. Scientific and common names of insect orders. Groups
consistent with older references, the non-insect indicated with an asterisk (*) do not occur in Pennsylvania.
hexapods are included as orders here. Species counts modified from Zhang (2011).

in the same habitats, and have similar morphology,

non-insect hexapods are often included with insects.

INSECT
Insects and other hexapods can be distinguished from
other arthropods by a number of features including the

STRUCTURE
presence of three main body regions or tagmata (head,
thorax, and abdomen), one pair of segmented antennae,
three pairs of segmented legs attached to the thorax,
and one pair of compound eyes. Insects are also the only Insects have three main body parts: the head, thorax,
arthropods that can have wings (although some “primi- and abdomen. The head contains sensory organs such as
tive” insects are wingless as adults). the eyes and antennae, as well as the mouthparts. The
thorax bears appendages used for locomotion, including
Insects are divided into 27 orders, which includes many three pairs of legs and, if they are present up to two pairs
groups such as beetles, flies, and butterflies that are wings. The abdomen contains the majority of the diges-
recognizable to most people. The non-insect hexapods as tive tract, as well as internal and external organs used for
considered here contain three orders. reproduction.

2
 48. All insects possess a body plan that can be divided into
three parts: the head, the thorax, and the abdomen
151. Ocelli are also called ‘simple eyes’ and are used to detect
HEAD light and shadows. You can see three of them sitting on the top
The head is the front-most (anterior) part of an insect’s of this wasp’s head, centered between her two compound eyes
body and includes the antennae, eyes, and mouthparts.
ANTENNAE
EYES Most insects have one pair of antennae at the front of
Most adult insects have compound eyes made up of the head (unlike some other arthropods, such as cray-
tiny facets, although some subterranean species may fish and lobsters, which have two pairs). Antennae are
lack eyes altogether. Compound eyes are used to see the sensory organs that are used to detect touch and chemi-
world around the insect, so visually oriented insects such cals that we perceive as odors or taste. Some insects also
as dragonflies can have large compound eyes of many use their antennae to detect sound. The size and shape
thousands of facets while subterranean insects may have of the antennae and the number of antennal segments
compound eyes made of a few or even one facet, if they vary greatly between insect groups and can be used for
are present at all. Because each facet sees a slightly dif- identification.
ferent image of the world, insects can see movement and
100 133
moving objects much better than vertebrate eyes (which
is why it’s so hard to kill a house fly!).

37 9

Antennae are important sensory organs and range widely in

their size and structure. Insects like this moth (left) and cedar
beetle (right) use long, fringed antennae to smell and locate
Insects’ compound eyes range in size and are used to view the mates
world around them. Dragonfly eyes (left) are very large and
composed of thousands of individual facets, while some insects, MOUTHPARTS
like ground beetle (right) have relatively smaller eyes Insect mouthparts, like their antennae, vary greatly
between orders of insects and species. The mouthparts of
Many insects also have 1–3 simple eyes called ocelli comprised of four parts that are derived from leg-like ap-
(singular ocellus) on the top of their heads. Ocelli are pendages – the labrum, mandibles, maxilla, and labium
composed of a single lens and cannot form images like – that work together to process food. Insect mouthparts
compound eyes can. Rather, they are used to detect are grouped by function, including chewing, piercing,
light and are associated with light-dark cycles, circadian siphoning, and lapping mouthparts, and are usually
rhythm, and determining the season. indicate what an insect eats.

3
 Chewing mouthparts are used to tear, cut, or crush
food and deliver it to the mouth opening. Some insects
have large chewing mouthparts that they also use
when competing against other males of the same
species.
81 10

160. This bumblebee is using siphoning mouthparts to access

the nectar deep inside of this thistle flower

Lapping mouthparts have been modified to act like a

sponge to lap up liquids. For example, this is how house-
Many beetles, such as these two pictured, use their mandibles flies and fruit flies eat.
to tear and cut food. Stag beetle males (left) rely on showing
off their oversized mandibles to find a mate THORAX
The thorax is the middle section (tagma) of an insect’s
Insects with piercing mouthparts have the same basic body and is located behind the head and in front of
components as insects with chewing mouthparts (i.e., the abdomen. The thorax of adult insects contains the
labrum, mandibles, maxilla, labium) except the parts appendages used for locomotion, including three pairs
are modified into long, thin stylets that form a hollow of legs and the wings (if they are present). The thorax is
tube. Piercing mouthparts have evolved multiple times often stiff with many internal folds that the muscles used
within insects, and how and which parts of the mouth- to control the legs and wings attach to.
parts are modified varies between groups. Piercing
mouthparts allow the insect to insert the mouthparts LEGS
into plants or animals on which they feed. The three pairs of jointed legs originate from the thorax.
Insect legs differ based on their mode of movement and
are often useful in identifying insects. Some examples of
different types of legs based on the insect’s movement
include walking, jumping, and swimming. Some legs
are adapted for specific uses such as carrying pollen or
capturing prey. The feet of insects often have small claws
or pads depending on their type of movement and the
environment they inhabit.

110 49

1. Mosquito saliva is directed into the host as they are feed-

ing, which includes a mix of proteins that prevent blood from
clotting and are anesthetic so that you don’t feel their stylet
when they are probing you

Siphoning mouthparts are similar to piercing mouth-

parts. The basic parts of the mouthparts have been
modified to form a tube which enabling the insect to
draw in fluids such as nectar. In general, siphoning This shore fly (left) has large, raptorial forelegs that aid in the
mouthparts are not stout enough to pierce into other capture of live prey. For grasshoppers (right), large, elongated
plants or animals. hindlegs are used for hopping and jumping

4
WINGS
The wings, like the legs, originate from the thorax.
Many, but not all, adult insects have wings. Wings vary
greatly between orders and species of insects and the
venation of insect wings can aid in identification. Some
wings are highly modified for uses other than flying.
For example, the front wings of beetles, which are
called elytra, are hardened for protection of the hind
wings and body. The hind wings of flies are modified
into halteres, which act like gyroscopes and aid in bal-
ance during flight. The wings of moths and butterflies
are covered with minute scales which give the wings
their color.
39 32

134. The internal anatomy of a scorpion fly. Most insects share

71 the same basic internal structure, but this can vary depending
Beetle, fly on their lifestyle
and butterfly
wings vary RESPIRATORY SYSTEM
dramatically Unlike mammals, birds, and other vertebrates, insects
in form and lack lungs and do not use blood to transport oxygen.
function Instead, insects almost exclusively rely on the passive
diffusion of air through a network of hollow, internal
branching tunnels (known as the tracheal system) to
acquire oxygen. The tracheal system extends throughout
the insect’s body and even into the wings. The openings
ABDOMEN of the tracheal system in the exoskeleton are called spir-
The abdomen is the rear-most main section of an in- acles. Spiracles are found on the thorax and abdomen,
sect’s body located behind the thorax. The abdomen is although the number of spiracles may be reduced in
sometimes hidden by the insect’s wings while mov- some insects or completely lost (as is sometimes the case
ing or at rest. Much of the digestive system is located with aquatic insects that have gills). The spiracles can be
within the abdomen, along with the insect’s internal selectively opened or closed depending on the specific
and external reproductive organs. Adult females of activities or behaviors an insect is engaging in.
many groups of insects have an ovipositor located at
the rear of the abdomen that is used to lay eggs. In CIRCULATORY SYSTEM
other groups, the last few segments of the abdomen are Insect circulatory systems are located along where a
modified into an ovipositor. Glands are common on backbone would be in animals with internal skeletons.
the abdomen used to produce various chemicals that The circulatory system is an open system with bodily
aid in communication. fluids flowing throughout the body, bathing the muscles
and organs (unlike the closed circulatory systems of
INTERNAL ANATOMY mammals and other vertebrates, where blood is routed
The internal anatomy of insects differs greatly from the through veins and arteries).
vertebrates we are most familiar with. A short de-
scription of the respiratory, circulatory, digestive, and Instead of having ‘blood’, insects transmit nutrients, hor-
nervous systems is below. mones and cells through a fluid called hemolymph. He-

5
molymph is mostly made of water but also includes a complete metamorphosis (holometaboly). Metamor-
small percentage of ions, carbohydrates, lipids, amino phosis is the term for the transition between stages of
acids, cells and other materials. The hemolymph flows insect development. Regardless of the type of devel-
freely throughout the body cavity to deliver nutrients opment, there is a general theme of progression from
and remove waste from the insect. It also has import- egg to immature to adult insect with fully developed
ant immune response functions, allowing for wounds legs, wings (if present), mouthparts, antennae, repro-
to be sealed by clotting, or by defending against inter- ductive organs.
nal parasites or other invaders. Insects don’t have a
centrally located heart like we do – instead, the hemo- Adult insects can lay anywhere from a few eggs to
lymph flows from the efforts of a tunnel-shaped dorsal many thousands of eggs. These eggs can take days to
vessel, or heart, in the abdomen, that pulls hemolymph months to hatch, with some eggs enduring the winter
in and pulses it forward towards the thorax and the before hatching. Insects that have specific hosts as lar-
head of the insect. From here, hemolymph spills out va are often laid on or near that host. The immature
of the aorta, kind of like a hose, before sloshing back insect’s main priority is to eat and grow. Immature
toward the posterior end of the body again. insects must molt to grow, with the stages between
molts being called instars.
DIGESTIVE SYSTEM
The digestive tract is relatively simple and goes from NO METAMORPHOSIS
the mouth of the insect to the abdomen where waste Some primitive insects develop with no metamor-
is excreted. Depending on their lifestyle, insects will phosis. These insects go from egg to immature to
have different specialized organs to cope with the adult with little change from the immature to adult
digestion of food, the absorption of nutrients and stages other than size. Immature insects that lack
waste excretion. Broadly speaking, however, insect metamorphosis look and function like the adults but
digestive systems include three functional regions - are slightly smaller and don’t have fully developed re-
the foregut holds the food, the midgut breaks down productive organs. Once the insect has functional re-
the food, and the hindgut processes and excretes the productive organs it is considered an adult, although
waste. it may continue to grow and molt. None of the groups
that are ametabolous possess wings as adults.
NERVOUS SYSTEM
The nervous system consists of a series of nerve centers 79. Incomplete metamorphosis is a common insect lifestyle
called the ganglia (singular ganglion) running along reflected in groups such as grasshoppers, cicadas, aphids and
the bottom (or venter) of the insect, which is differ- stoneflies
ent from vertebrate species where the
nervous system runs up and down the
spine. Primitively, each segment of the
insect body has a separate ganglion and
associated nerves that act like control
switches for that segment. The insect
“brain” is really a fusion of the nerves
associated with the fused segments
of the head, which correspond to the
antennae, possibly the eyes, and each of
the paired mouthparts.

INSECT GROWTH AND

DEVELOPMENT
Insect growth and development is
distinctive and aids in the classification
of insects. There are three main types of
insect development: no metamorphosis
(ametaboly), incomplete metamorphosis
(paurometaboly and hemimetaboly), and

6
77. Complete metamorphosis is common to many insect groups including beetles, bees, butterflies, and flies.

INCOMPLETE METAMORPHOSIS the soil, leaf litter, crevices of tree bark, between rocks,
Incomplete metamorphosis contains three stages: and sometimes in the open with excellent camouflage.
egg, nymph, and adult. There are two broad classi- The pupa transitions into the adult insect that then
fications of incomplete metamorphosis: paurome- reproduces and starts the cycle over again. Bees, bee-
taboly and hemimetaboly. Immatures of paurome- tles, moths and butterflies are examples of insects that
tabolous insects are called nymphs, are terrestrial, undergo complete metamorphosis.
and usually resemble the adult insect but lack wings.
Grasshoppers and true bugs are examples of pau-
rometabolous insects. Immatures of hemimetabolous
insects are usually called naiads, are aquatic, and do
not strongly resemble the adult insect. Dragonflies

INSECT ORDER
and damselflies are examples of hemimetabolous
insects. Incomplete metamorphosis does not include

DESCRIPTIONS
the pupa stage and nymphs transition directly to
adults during the final molt.

COMPLETE METAMORPHOSIS The following summaries of currently accepted insect

Complete metamorphosis contains four stages: egg, orders include the scientific order name, the common
larva, pupa, and adult. The egg hatches into a larva name, examples of insects in the order, the type of
that eats, grows and molts into multiple instars, and mouth parts, the type of metamorphosis, and other
then pupates. Some pupae will ‘spin’ their own silk distinguishing characteristics of the order. With new
cocoons to pupate in. Pupae might also be surround- information, the way insects are classified is subject
ed with cut leaf pieces or other natural material. to change over time. The orders are arranged alpha-
Pupae can be found in protected locations such as in betically.

7
BLATTODEA COLEOPTERA
COCKROACHES, TERMITES BEETLES

• Chewing mouthparts • Chewing mouthparts

• Two pairs of wings • Two pairs of wings
• Forewings hardened into leathery • Forewings hardened into elytra
tegmina (cockroaches)
• Wings, when present equal in size and
• Complete metamorphosis
shape (termites; only reproductives
have wings)
• Incomplete metamorphosis

All cockroaches (4,400 known species) and termites Coleoptera translates to ‘sheath wing’ and includes all
(3,000 known species) are classified in Blattodea. These beetles, which is the largest insect order of them all con-
two insect groups often appear and behave very differ- taining over known 400,000 species. Beetles are found all
ently from one another. They were originally separated over the world and live in almost every habitat imag-
into two different orders until 2008, when we learned inable (except for in the sea or polar regions)! They are
from DNA analysis that termites arose from cockroach easy to identify from the hardened forewings, or ‘elytra’,
lineages. It may seem hard to believe, but termites and that shield the hindwings which are protected at rest and
cockroaches share many similar behaviors. They both used during flight. Beetles can be beneficial predators,
(to varying degrees) engage in social behavior, subsist like lady beetles or ground beetles that eat insect pests
on decaying organic matter, and primarily live in wet, like aphids or caterpillars. However, some beetle species
warm environments. While most termites must work are themselves troubling insect pests, like the Colorado
cooperatively to care for their young and defend their potato beetle or root weevils, that eat up agricultural
nest, cockroaches are usually more independent but often crops. Charles Darwin was a famous beetle collector and
benefit from cooperation with their fellow cockroaches. frequently referred to them in his writings on natural
A few groups of cockroaches are known to exhibit more selection and evolution.
complicated social interactions, which are similar to
primitive termites.

4 5 12 13

6 These termites (top left, 14 Beetles assume a diversity

top right) and cockroaches of shapes and size, but
(bottom) are both in the common to all beetles are
order Blattodea the presence of hardened
forewing, or ‘etlyra’ that
protect the hind wings
when not in use.

8
COLLEMBOLA DERMAPTERA
SPRINGTAILS EARWIGS

• Chewing mouthparts • Chewing mouthparts

• Wings absent • Two pairs of wings
• No metamorphosis • Strong pincers (cerci) at end
• Collophore (grooming structure) of abdomen
and often a furcula (jumping • Incomplete metamorphosis
organ) present

Springtails are one of the three groups of non-insect There are 2,000 known species in the order Dermaptera
hexapods that are closely related to insects. More (earwigs), of which only 25 occur in North America.
than 8,200 species have been described worldwide. You may be familiar with the earwig’s oily brown
Springtails are detritivores that feed on decaying plant coloration, flattened elongated body and abdominal
material, algae and lichen, and rarely on the roots of pincers. Earwigs are often found in damp crevices and
plant seedlings. They are found in moist environments, they are most active at night. Many earwig females
such as leaf litter, under the bark of fallen logs, and in are devoted mothers and provide care and protection
mulch, although a few species can tolerate drier con- to their offspring, which is uncommon for most insect
ditions and might be found on sidewalks and similar species. Earwigs are scavengers and eat diverse foods
environments. Springtails use a pair of specialized ranging from decaying organic matter to small insect
organs on the underside of the body to jump up to 100 prey. Recently, earwigs have been found to serve as
times their body length, usually to escape predators. important predators of aphid pests in apple orchards.

18 19 25 26

17

23 Earwig mothers are often

known to care for their
offspring (top left) and are
easily identifiable from the
abdominal pincers at the
end of their bodies. The
pincers are used for many
different purposes, includ-
ing as a defense against
predators, to catch prey,
or in mating and courtship
behaviors.

9
DIPLURA DIPTERA
TWO-PRONGED BRISTLETAILS FLIES

• Chewing mouthparts • Mouthparts highly variable

• Wings absent • Piercing/sucking
• Two long cerci on the end of the • Cutting/lapping
abdomen • Sponging
• No metamorphosis • One pair of wings
• Hind wings developed into halters
• Complete metamorphosis

Two-pronged bristletails are one of the groups of non-in- While an estimated 1,000,000 species are in the Diptera
sect hexapods. In North America, they are divided into order, we have only described about 125,000 of them
two groups based on the appearance of the cerci – one today. Common to all flies is their two wings and large
group has long, thread-like cerci and the other has the compound eyes. Flies are, without a doubt, one of the
cerci developed into stout pinchers. Two-pronged bris- most economically impactful insects in human society
tletails live in leaf litter and other moist environments. today. Many flies including bee flies and hover flies are
Some species are detritivores that feed on decaying plant often underappreciated as critical pollinators of wild and
material, others feed on living plant material, while oth- managed ecosystems, and flies often serve as model or-
ers are predators that feed on small arthropods. Approxi- ganisms for scientific research. Mosquitos and houseflies
mately 125 species are known from North America. are well-known to transmit diseases such as malaria or
cholera (respectively) to millions of people every year.

31 32

29

33 Flies display an astonishing

diversity of lifestyles and
behaviors

30

34

10
EMBIOPTERA EPHEMEROPTERA
WEBSPINNERS MAYFLIES
(not known to occur in Pennsylvania)

• Chewing mouthparts • Chewing mouthparts (vestigial as

• Two pairs of wings or wingless adults)

• Tarsi of forelegs developed to spin silk • Two pairs of wings held vertically
at rest
• Incomplete metamorphosis
• Incomplete metamorphosis
• Immatures are aquatic

The webspinners of the order Embiidina are found in The order name Ephemeroptera translates to “ephemeral
tropical and subtropical regions and live socially in silk wing”, which refers to the short lifespan mayflies have as
galleries that are collectively spun from glands on their adults. Since adult mayflies lack functional mouthparts,
front legs. Over 400 species are known, all between 0.6 these species typically live just a few hours to a few days
and 0.8 inches in length. The silken galleries provide or weeks. Mayflies spend most of their lifetime under-
protection to social colonies from predation and maintain water as nymphs in aquatic creeks and streams, where
moisture, and are typically built on rocks, trees or leaf they breathe through gills located on the abdomen. The
litter. Adult males lack mouthparts and only live long diversity and abundance of mayfly and other aquatic
enough to breed while adult females are flightless and insect species can be and often are sampled in waterways
eat a variety of plant materials. Female flightlessness as an indicator of stream health. Adults are easy to iden-
limits the rate of dispersal of webspinning colonies and tify because of the way they hold their wings upright at
they are not generally considered to be of agricultural rest. They are active in Pennsylvania between April and
concern. September, depending upon the species. While we know
of over 3,000 mayfly species worldwide, only about 230
species are found in Pennsylvania.

40 46 These terrestrial mayfly

adults look very different
from their aquatic,
immature forms

44

41

47

11
HEMIPTERA HYMENOPTERA
TRUE BUGS, LEAFHOPPERS, APHIDS BEES, WASPS, SAWFLIES, ANTS

• Piercing mouthparts • Chewing mouthparts

• Two pairs of wings • May be modified into chewing/
lapping mouthparts
• Forewings modified into hemelytra
• Incomplete metamorphosis • Two pairs of membranous wings
• Complete metamorphosis

Insects in this order are commonly referred to as true Bees, wasps, ants and sawflies are nested within the or-
bugs. The order name Hemiptera translates to ‘half-wing’, der Hymenoptera, which is Latin for ‘membrane wing’, or
which refers to the way the forewings are modified into ‘married wing’, depending on who you ask. Both inter-
hemelytra that are partially hardened and partially pretations are accurate, as all winged insects in Hyme-
membranous. More than 50,000 to 80,000 species occur noptera have two pairs of membranous wings, in which
worldwide and they display an astonishing diversity of a series of hooks connect, or ‘marry’, the hind wings to
appearances and lifestyles. Common to all true bugs is the fore wings for flight. Hymenoptera is a large order
the presence of piercing/sucking mouthparts, which can (over 153,000 species) which plays all sorts of interesting
pierce substrates like plant stems or insect or vertebrate ecological roles in the environment and ranging from
prey to get to the nutritious fluids inside. True bugs predators to parasitoids to pollinators. Honey bees are
share a deep and wide-ranging association with human the most familiar species within the order, as they pro-
history. Some true bugs, such as the scale insects, are cul- vide essential pollination services to fruit, nut and seed
tivated for the production of cochineal dye and shellac, crops around the world. However, most Hymenopterans
and others serve as effective biological control agents as do not live socially like honey bees do: a lot of variety
predators of agricultural pests. Unfortunately, other true in cooperative living is represented in this insect group,
bugs can impact human health or are major crop pests. ranging from completely solitary insects to fully eusocial
For example, kissing bugs in Central America can trans- colonies.
mit Chagas disease, which affects millions of people in
that region every year. Bed bugs are another well-known
pest that, while they don’t transmit disease, are annoying
60 61
and pestiferous nonetheless. Aphids, planthoppers and
mealybugs are common agricultural and nursery pests
that often require pesticide applications to control.

51 50

62 Hymenopterans are
extremely diverse
and express a di-
versity of beautiful
forms
57

12
LEPIDOPTERA MANTODEA
MOTHS AND BUTTERFLIES MANTIDS

• Siphoning mouthparts • Chewing mouthparts

• Two pairs of wings • Two pairs of wings
• Complete metamorphosiss • Forewings modified into leathery
tegmina
• Front legs adapted to capturing
prey (raptorial)
• Incomplete metamorphosis

About 180,000 species of moths and butterflies are in the Mantodea includes all praying mantises, of which 2,400
order Lepidoptera. ‘Lepidoptera’ is from Ancient Greek species are known globally. These charismatic, carnivo-
and means scale wing, which refers to the flattened rous insects are easy to spot because of their triangular
hairs, or scales, that underly the beautiful, colorful and shaped head, long “neck”, and grasping, raptorial fore-
patterned wings they are known for. Butterflies and legs. Mantids hunt for their prey as ambush predators or
moths are often recognized as important pollinators through slow and steady stalking. They are exceptional
because the adults sip nectar from flowers. However, hunters and have been known to catch not just other
these pollination services are generally not as efficient as insects (both beneficial and pestiferous), but also small
those provided by bees, wasps and flies, as they are less vertebrates such as lizards, fish, frogs or birds. Man-
effective at moving pollen between flowers. Many moth tids are easiest to spot in the late summer and early fall
and butterfly species share a tight evolutionary associa- during their mating season. There are just five mantid
tion with specific host plants, which means their very ex- species known to occur in Pennsylvania, and just one of
istence is highly dependent on having the right flowering those, the Carolina mantis, is native to the United States.
plants available to them for growth and reproduction. In
Pennsylvania, the frosted elfin, the regal fritillary and the
monarch butterfly have all become ‘critically imperiled’
due to a lack of available native host plants (yellow and
wild indigo, violets, and milkweed, respectively) where
they occur.
84

69

85
70 68

13
MECOPTERA MEGALOPTERA
SCORPIONFLIES DOBSONFLIES, ALDERFLIES

• Chewing mouthparts • Chewing mouthparts

• Two pairs of wings • Males often have large mouthparts
• Complete metamorphosis • Two pairs of wings
• Head often elongated • Complete metamorphosis

Mecoptera, or scorpionflies, are perhaps less universally Dobsonflies, alderflies and fishflies are in the order Meg-
known than other more popular or speciose orders. Scor- aloptera and are characterized by the adult’s very large
pionflies are so-named because males of many species wings relative to their body size. The larvae are aquatic
have enlarged genitals that look somewhat like a scorpi- predators that grow slowly, taking between one and
on’s stinger. Most of the 600 known species have ranges five years to reach maturity. While there are 300 known
restricted to tropical regions. Pennsylvania is home to species in this order, we do not understand very much
just 11 species. Different species are active at different of their biology due to their short adult lives, nocturnal
times of year, including in the middle of winter for one habits, and limited human encounters in the wild.
family called snow scorpionflies. Scorpionflies thrive in
damp, moist environments and are mostly scavengers of
decaying plant matter or dead, soft-bodied insects.

88 90 92 93

91

94 Male dobsonflies (93) are

easily recognizable from
the large mandibles they
use to attract female mates.
Immature dobsonflies
(94) are often called
‘hellgrammites’ and use
their strong mandibles to
catch and eat prey.

14
MICROCORYPHIA NEUROPTERA
JUMPING BRISTLETAILS LACEWINGS, ANTLIONS

• Chewing mouthparts • Chewing mouthparts

• Wingless • Two pairs of wings
• No metamorphosis • Wings have net-like venation
• Complete metamorphosis

The Microcoryphia are wingless insects that are com- Neuroptera includes 600 species of lacewings and
monly called jumping bristletails. They are the most antlions. They have large, membranous wings which
evolutionarily primitive insects that exist today and have with heavy venation. Nearly all insects in this order are
a cosmopolitan distribution. There are over 500 species terrestrial, live in vegetation and feed on soft-bodied prey
of jumping bristletails, which are so-named because of such as aphids, scale insects and mites. Species that are
their three-pronged tails and because they can perform not predatory visit flowers and eat pollen and nectar.
some impressive and acrobatic jumps to get around. The cocoons of pupating Neuropterans are frequently
These insects are small, usually brownish-yellow in color composed of organic debris that aid in camouflage at this
and found in damp, dark environments like in leaf litter vulnerable stage.
or in other decomposing materials. Individual jumping
bristletails can live for up for four years and it can take a
full two years for them to reach sexual maturity.

96 102

95 101

98 103

15
NOTOPTERA ODONATA
ICE CRAWLERS, ROCK CRAWLERS, HEEL- DRAGONFLIES, DAMSELFLIES
WALKERS (do not occur in Pennsylvania)

• Chewing mouthparts • Chewing mouthparts

• Wingless • Two pairs of wings
• Incomplete metamorphosis • Wings cannot be folded over
the abdomen
• Incomplete metamorphosis
• Immatures are aquatic, with
extendable labrum

Notoptera is a small order of wingless insects and There are about 5,900 species of damselflies and drag-
includes the ice crawlers (suborder Grylloblattodea) and onflies that have been described in the order Odonata.
rock crawlers or gladiators (suborder Mantophasmato- Most of their life is lived underwater as nymphs and they
dea). There are fewer than 60 living species included are most active as flying adults in Pennsylvania during
in the order, although they were more diverse in the June and July. Both nymphal and adult stages are pred-
past and are known from a number of extinct fossil ators of smaller insects. In adulthood, nearly everything
groups. Ice crawlers in North America are associated that Odanates do is performed on the wing, including
with glaciers and ice caves of western mountain ranges hunting, eating and mating. This order is particularly
and cannot survive the heat from being held in a human sensitive to changes in water quality and climate, making
hand. They are often nocturnal and eat insects that are damselflies and dragonflies valuable ecological indica-
blown onto glaciers or into caves and killed or immobi- tors of freshwater systems.
lized due to the cold. Due to their limited distribution,
these rare insects are infrequently encountered and not
much of their biology is known. Rock crawlers were
known only from amber fossils until living specimens
114 111
were discovered in Namibia in 2002. Since then, 21 extant
species have been described, all of which are only found
in Africa.

108

115

109

16
ORTHOPTERA PHASMATODEA
GRASSHOPPERS, CRICKETS, KATYDIDS WALKING STICKS

• Chewing mouthparts • Chewing mouthparts

• Two pairs of wings • Winged or wingless
• May be wingless • If winged, forewings developed
into leathery tegmina
• Hind legs typically enlarged for
jumping • Long, skinny body
• Incomplete metamorphosis • Incomplete metamorphosis

Grasshoppers, locusts, katydids and crickets are all in the The walking sticks and leaf insects, classified in the
order Orthoptera, representing over 20,000 species glob- order Phasmatodea, are found on every continent but
ally. They are easiest to recognize from the sounds that Antarctica. They are highly camouflaged to resemble
they make by rubbing their wings or legs against each twigs or leaves, and primarily feed on leaves. There are
other, which is important for courtship, and are active over 3,000 known species, although only two occur in
throughout the spring, summer and fall in Pennsylvania. Pennsylvania. When walking sticks are approached by
Locusts pose unique and difficult agricultural challeng- potential predators, rather than remaining still, they
es, as demonstrated by their decimation of West African often can expel defensive compounds, engage in a showy
crops in 2020 and 2021. While primarily herbivorous, display, or make loud, disruptive noises by rubbing their
most species are not of significant agricultural concern. wings together to scare the predators away. Walking
sticks are susceptible to habitat fragmentation, pesticide
use and collection for the pet trade in certain parts of
117 the world. Some of the largest insects known today are
walking sticks, which can reach over 20 inches in length
in tropical regions.

122

118

121

17
PLECOPTERA PROTURA
STONEFLIES CONEHEADS

• Chewing mouthparts • Chewing mouthparts

• Two pairs of wings held flat along • Wings absent
back at rest • No metamorphosis
• Incomplete metamorphosis
• Immatures are aquatic

Plecoptera includes over 3,500 species of stoneflies. The Protura are one of three groups of non-insect Hexapods
nymphs are aquatic and require between one and four that are closely related to insects. Like two-pronged
years to reach maturity, which is usually short-lived. bristletails and springtails, coneheads are found in moist
Stoneflies are highly sensitive to polluted and poorly leaf litter. However, unlike the other two groups, they are
oxygenated water, so are often used as water quality extremely small (<2 mm) and unlikely to be seen without
indicators like mayflies (Ephemeroptera) and caddisflies a microscope. While they are tiny and inconspicuous,
(Trichoptera). Stonefly nymphs are popularly referenced more than 750 species have been described worldwide
by fly fisherman in the making of lures for flyfishing. The and 80 species are known to occur in North America.
adults are recognizable from paired cerci projecting from Unlike insects, springtails, and two-pronged bristletails,
the tip of the abdomen and their beautifully veinated coneheads lack antennae. Instead, their first pair of legs
wings that lay flat against the body (unlike mayflies). are modified into sensory organs that are held above and
in front of the body while the second and third pairs of
legs are used for walking.

124 125 127

126

123

18
PSOCODEA RAPHIDIOPTERA
PARASITIC LICE, BOOK LICE, BARK LICE SNAKEFLIES
(do not occur in Pennsylvania)

• Piercing or chewing mouthparts • Chewing mouthparts

• Wingless or two pairs of wings • Two sets of wings
• Incomplete metamorphosis • Complete metamorphosis
• Parasitic groups associated with
bird or mammal hosts

Book lice, bark lice and true lice are all housed within Snakeflies are predatory insects that possess a notably
the order Psocodea, which includes over 11,000 species in elongated thorax. While there are just 260 living species,
total. Humans are most familiar with the true lice, which many extinct species are known from fossils and they
are common blood feeding parasites capable of vectoring were apparently much more diverse in the past. Snake-
diseases such as typhus. Book lice and bark lice are less flies are mostly found in temperate regions and in North
frequently encountered and are small scavenging insects America limited to areas west of the Rocky Mountains.
the primarily feed on fungi, algae, lichen and other Snakeflies live beneath the bark of trees, in small crevices
organic detritus. Book lice get their name for their novel in rocks or among leaf litter, and can require up to three
association with old books, from which they survive on years for larvae to reach maturity.
the paste used in the bindings. Bark lice live on the bark
of tree trunks and are easy to spot from the characteristic
webbing they produce (which is not harmful to the trees).
There is much variation in the appearance of different
lice species; some are wingless, some lack ovipositors and
they exhibit a range of body shapes.

132

128 129

131

130

19
SIPHONAPTERA STREPSIPTERA
FLEAS TWISTED-WING PARASITES

• Chewing mouthparts • Piercing mouthparts

• Wingless • Males have one pair of wings with
• Complete metamorphosis the other pair reduced to small
appendages
• Complete metamorphosis

There are over 2,500 species of fleas, all of which are Strepsipterans are also known as the twisted-wing
small, dark-colored, flightless insects that feed on the parasites. While 530 species are known worldwide, only
blood of various bird and mammal hosts. Fleas are small about 110 occur within the United States. Strepsipterans
with a narrow or flattened body plan that make it easy survive as internal parasites that reside inside various
for them to navigate the feathers or hairs of their hosts. bee, wasps, grasshopper and true bug species. They
They are well known for their jumping abilities, which exhibit a specialized developmental habit known as
comes from specially adapted hind legs that store energy hypermetamorphism whereby the larvae take on two
for propulsion. Fleas cannot live for more than a few days distinct physical forms before reaching sexual maturity: a
as larvae or adults without a host. dispersing, crawler form to find the host and then a phys-
ical form lacking any distinctive features once inside the
host. Upon pupation, adult male and female body plans
vary substantially. Male strepsipterans have one pair of
wings (the forewings are reduced), large eyes and legs
while female lack these parts and lives her life largely
immobile inside the host with just her copulatory organs
exposed to the environment to mate. Male strepsipterans
lack functional mouthparts and live only long enough
to mate, so are rarely seen or collected. Eggs hatch in the
136 137 host as crawlers and the cycle begins again.

141 142

138 135
139

20
THYSANOPTERA TRICHOPTERA
THRIPS CADDISFLIES

• Punching/sucking mouthparts • Piercing mouthparts

• Two pairs of wings • Two pairs of wings held like a pup-
• Wings fringed tent over body
• Incomplete metamorphosis with a • Wings covered in hair
pupa-like resting stage • Complete metamorphosis
• Immatures are aquatic

Thrips are small (usually 1mm or less), slender insects The order Trichoptera, which are commonly called
with fringed wings that feed on plants or are predatory caddisflies, contains approximately 14,500 species
on other small insects. Their mouthparts are unlike those worldwide. Adult caddisflies are usually nocturnal and
of any other insect group – the left mandible is used resemble moths, which they are closely related to. The
to “punch” a hole into the food and then long, probos- wings of caddisfly adults are covered in hairs, which
cis-like mouthparts are used to suck the out the contents have the same origin as the flattened scales of moths
of the plant or animal. Cycad-associated thrips are and butterflies. Caddisfly larvae are aquatic and are
believed to have been the first pollinivores and predat- best known for their tendency to craft protective cases
ed the evolution of bee and butterflies. Thrips are most around themselves from nearby sand, gravel, shells,
well-known as a major agricultural pest of crops, as their leaves, sticks, and other material. The structure and
feeding on plant tissues can damage crops and they can preferred materials for case construction vary by species
vector over 20 known viruses that can permanently dam- and can aid in identifying caddisflies, often to the level
age entire orchards. They are quick to develop chemical of genus even without physical examination of the larva
resistance to pesticide applications and represent some of inside. Trichoptera larvae are frequently associated with
the fastest-spreading invasive species in the world. creeks, streams and rivers and are usually intolerant of
pollution, so the presence or absence of caddisflies can
help determine whether a body of water is polluted or
not. Larvae are important prey for fish and other larger,
aquatic insects.

144 149

148

145

147

21
ZORAPTERA ZYGENTOMA
ZORAPTERANS SILVERFISH, FIREBRATS

• Chewing mouthparts • Chewing mouthparts

• Two pairs of wings or wingless • Wingless
• Incomplete metamorphosis • No metamorphosis

Insects in the order Zoraptera are also known as the an- Zygentoma includes 550 described species. Many species
gel insects. Of the 55 living and extinct members of this are commonly referred to as silverfish because of the
order, only two are known to occur in the U.S. They are silvery scales that cover their bodies. They are nocturnal,
small, soft bodied insects that generally live socially in small, wingless insects that are cosmopolitan and fre-
rotting wood, under the bark of fallen trees, and are often quently found in dusty basements, attics, sinks, kitchens
associated with termite colonies. Zorapteran colonies or bookcases. They are detritivores that can consume a
include one dominant male who mates with the females diverse array of materials. In nature, this makes them
in the colony. As detritivores, these insects are excellent important decomposers.
custodians of the environment as they eat up and help
break down decaying organic matter.

156
159

154

158

155

22
INSECT day-active insects. Minimizing the amount of outdoor
lighting as much as practical and utilizing motion-ac-

CONSERVATION tivated lights can reduce the impact on insects. Using

yellow lights also has less impact than white lights
that are attractive to many insects.
Insect declines have been occurring globally over the
recent decades. Many factors contribute to insect decline,
including habitat loss and degradation, pesticide use, and
outdoor lighting.

HABITAT
Habitat loss, degradation, and fragmentation are leading
factors of insect decline. Habitat loss is straightforward –
without places to live, feed, and breed, insects cannot ex-
ist. Habitat degradation includes a variety of issues that
make otherwise healthy habitat unsuitable to insects. For 3
example, the presence of invasive plant species that out-
compete the native plants Pennsylvania’s insects evolved
with degrade habitat since many insects cannot utilize

GLOSSARY
the invasive plants. Habitat fragmentation is the breaking
up of healthy habitat into smaller blocks. Insects often
cannot travel far, so large gaps between habitat can stop
groups of insects from mating. Once geneflow between ABDOMEN: Rear most body segment of an insect
patches of habitat slows or stops, isolated populations can
become inbred and eventually die out, even in otherwise COCOON: The case in which the pupa transforms into
appropriate habitat. an adult

Protecting natural habitats and a planting diversity of COMPOUND EYE: An eye composed of many small eyes
native plants are some of the easiest ways to promote
habitat for native insects. Since many pupae are found in EXOSKELETON: The hard outer “skin” of the insect
leaf litter, leaving an area of leaf litter around trees in the
autumn can greatly benefit insects. HALTERE: Small knobbed or club-like vestigial hind
wing of flies
PESTICIDES
Inappropriate pesticide use is a direct threat to insect HOST: The living organism on which another organ-
survival so minimizing pesticide use can benefit native ism depends for survival. Monarch caterpillars rely
insects. Utilizing Integrated Pest Management (IPM) to on milkweed host plants for development
the greatest extent possible may lead to less dependence
on pesticides and healthier insect communities. Integrat- INSTAR: The stages of an insect between molts
ed pest management utilizes thresholds of acceptable
damage, the use of natural predators to control pests, INTEGRATED PEST MANAGEMENT: Sustainable deci-
practices such as crop rotation, and finally judicial sion-making process that utilizes different methods
pesticide use if needed. Some considerations when using to reduce risks from pests and to native insects. The
pesticides include timing of pesticide use, the specific process utilizes thresholds of acceptable damage,
pesticide selected, and the method of application. For a variety of practices to reduce pest risk, and still
homeowners, allow the propagation and blooming of allows for judicial pesticide use if needed.
dandelions and clovers in lawns to provide important
forage to beneficial insects such as bees. LARVA: The insect stage between the egg and pupa for
insects going through complete metamorphosis
OUTDOOR LIGHTING
Artificial outdoor lighting can disrupt insect reproduc- METAMORPHOSIS: The change in structure and size of
tive activity, especially of nocturnal insects but also of an insect as it develops

23
NYMPH: The immature stage of an insect between the egg 5. “Blattodea 2” by Pauline Horn on flickr.com has been
and adult going through incomplete metamorphosis modified (cropped) and is used under a CC BY-NC-
ND 2.0 license
OCELLUS: Simple eye 6. Graham Montgomery / Bugguide.net
8. “bumblebee 1” by Barry Dale Gilfry on flickr.com
OVIPOSITOR: Part of the insect adapted for laying eggs has been modified (cropped) and is used under a CC
BY 2.0 license
PARASITE: An organism that lives on or in another organ- 9. “Carabidae 1” by Biological Museum, Lund Univer-
ism from which it feeds. Does not usually kill the host sity: Entomology on flickr.com has been modified
(cropped) and is used under a CC BY 2.0 license
PARASITOID: A larval insect that lives on or in another 10. Salvador Vitanza / Bugguide.net
organism from which it feeds, usually resulting in the 12. Tom Murray / Bugguide.net
death of that organism. 13. Tom Murray / Bugguide.net
14. Tom Murray / Bugguide.net
PREDATOR: An animal that kills another animal for food 17. “Collembola 1” by Philippe Garcelon on flickr.com
has been modified (cropped) and is used under a CC
PUPA: The insect stage between a larva and adult for BY 2.0 license
insects going through complete metamorphosis 18. “Collembola 2” by Philippe Garcelon on flickr.com
has been modified (cropped) and is used under a CC
SCLEROTIZATION: Hardening of the exoskeleton BY 2.1 license
19. “Collembola 3” by Philippe Garcelon on flickr.com
THORAX: The middle body segment of an insect. The legs has been modified (cropped) and is used under a CC
and wings join the thorax BY 2.2 license
23. Brad Smith / Bugguide.net
25. Mardon Erbland / Bugguide.net
26. “Dermaptera 7” by Katja Schulz - Own work. Li-

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of Nebraska–Lincoln fact sheet EC1588. Available online 32. Tom Murray / Bugguide.net
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pdfs/ce/resources/ce-ec1588-introduction-to-entomology. 34. Tom Murray / Bugguide.net
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40. Alex Wild / alexanderwild.com
41. Alex Wild / alexanderwild.com

PHOTO CREDITS 44. Tom Murray / Bugguide.net

46. Alex Wild / alexanderwild.com
47. Travis MacClendon / Bugguide.net
1. “Aedes aegypti female 1” by jentavery on flickr.com 48. DJ McNeil, Penn State
has been modified (cropped) and is used under a CC 49. “Grasshopper 1” by Jim, the Photographer on flickr.
BY 2.0 license com has been modified (cropped) and is used under
3. Peggy Butler / pafireflyevents.org a CC BY 2.0 license
4. “Blattodea 1” by Judy Gallagher on flickr.com has 50. Tom Murray / Bugguide.net
been modified (cropped) and is used under a CC BY 51. Tom Murray / Bugguide.net
2.0 license 57. Tom Murray / Bugguide.net

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59. “hornworm 1” by Peter Miller on flickr.com has been 2.0 license
modified (cropped) and is used under a CC BY-NC- 115. “Odonata 5” by Gustaaf Prins on flickr.com has been
ND 2.0 license modified (cropped) and is used under a CC BY 2.0
60. Tom Murray / Bugguide.net license
61. Tom Murray / Bugguide.net 117. Tom Murray / Bugguide.net
62. Tom Murray / Bugguide.net 118. Tom Murray / Bugguide.net
68. Alex Wild / alexanderwild.com 121. Tom Murray / Bugguide.net
69. Tom Murray / Bugguide.net 122. “Phasmatodea 1” by Yankech gary on flickr.com has
70. Tom Murray / Bugguide.net been modified (cropped) and is used under a CC BY-
71. Tom Murray / Bugguide.net ND 2.0 license
77. DJ McNeil, Penn State 123. “Plecoptera 1” by Ryszard on flickr.com has been
79. DJ McNeil, Penn State modified (cropped) and is used under a CC BY-ND
81. Ken Childs / Bugguide.net 2.0 license
84. Dave Barker / Bugguide.net 124. “Plecoptera 2” by Katja Schulz on flickr.com has
85. Clay Nichols / Bugguide.net been modified (cropped) and is used under a CC BY
88. Tom Murray / Bugguide.net 2.0 license
90. “Mecoptera 5” by Judy Gallagher on flickr.com has 125. “Plecoptera 3” by budak on flickr.com has been
been modified (cropped) and is used under a CC BY modified (cropped) and is used under a CC BY-NC-
2.0 license ND 2.0 license
91. “Mecoptera 6” by nutmeg66 on flickr.com has been 126. “Protura 1” by Andy Murray on flickr.com has been
modified (cropped) and is used under a CC BY-NC- modified (cropped) and is used under a CC BY-SA
ND 2.0 license 2.0 license
92. “Megaloptera 1” by Charlie Jackson on flickr.com has 127. Matt Bertone / Bugguide.net
been modified (cropped) and is used under a CC BY 128. Tom Murray / Bugguide.net
2.0 license 129. Tom Murray / Bugguide.net
93. “Megaloptera 2” by Tulio Bertorini on flickr.com has 130. Tom Murray / Bugguide.net
been modified (cropped) and is used under a CC BY- 131. “Raphidioptera 1” by Frank Vassen on flickr.com has
NC-ND 2.0 license been modified (cropped) and is used under a CC BY
94. “Megaloptera 3” by batwrangler on flickr.com has 2.0 license
been modified (cropped) and is used under a CC BY- 132. “Raphidioptera 2” by Jorge Almeida on flickr.com
NC-ND 2.0 license has been modified (cropped) and is used under a CC
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96. Charley Eiseman / Bugguide.net 133. “Rhipicera 1” by Jean and Fred on flickr.com has
98. “Microcoryphia 4” by Bruce Marlin - Own work. been modified (cropped) and is used under a CC BY
Licensed under CC BY-SA 3.0 via Wikimedia Com- 2.0 license
mons 134. Michael Skvarla, Penn State
100. “moth head 1” by Darius Baužys on flickr.com has 135. Lynette Elliott / Bugguide.net
been modified (cropped) and is used under a CC BY- 136. Tom Murray / Bugguide.net
SA 2.0 license 137. Tom Murray / Bugguide.net
101. Tom Murray / Bugguide.net 138. Tom Murray / Bugguide.net
102. Tom Murray / Bugguide.net 139. “Strepsiptera 1” by Will George on flickr.com has
103. Tom Murray / Bugguide.net been modified (cropped) and is used under a CC BY-
108. “Notoptera 1” by Marshal Hedin on flickr.com has NC 2.0 license
been modified (cropped) and is used under a CC BY- 141. “Strepsiptera 3” by maxson.erin on flickr.com has
SA 2.0 license been modified (cropped) and is used under a CC BY
109. “Notoptera 2” by P.E. Bragg - Own work. Licensed 2.0 license
under CC BY 3.0 via Wikimedia Commons 142. Mike Quinn / Bugguide.net
110. “Ochthera 1” by Ian Jacobs on flickr.com has been 144. “Thysanoptera 2” by Judy Gallagher on flickr.com
modified (cropped) and is used under a CC BY-NC has been modified (cropped) and is used under a CC
2.0 license BY 2.0 license
111. Tom Murray / Bugguide.net 145. “Thysanoptera 3” by Katja Schulz on flickr.com has
114. “Odonata 4” by my hobby on flickr.com has been been modified (cropped) and is used under a CC BY
modified (cropped) and is used under a CC BY-NC 2.0 license

25
147. Tom Murray / Bugguide.net
148. Tom Murray / Bugguide.net
149. Tom Murray / Bugguide.net
151. “Vespid head 1” by Janet Graham on flickr.com has
been modified (cropped) and is used under a CC BY
2.0 license
154. Steven Wang / Bugguide.net
155. Steven Wang / Bugguide.net
156. Steven Wang / Bugguide.net
158. “Zygentoma 2” by Judy Gallagher on flickr.com has
been modified (cropped) and is used under a CC BY
2.0 license
159. “Zygentoma 3” by Chris on flickr.com has been mod-
ified (cropped) and is used under a CC BY-ND 2.0
license
160. Natalie Boyle, Penn State

Cover photographs taken by Darya Alvarez and Natalie Boyle,

Penn State

26