Entomology
Janet Spencer
Extension Agent, ANR
Isle of Wight County
Entomology
The study of insects
Dominant groups of animals on earth today
Life on earth:
Modern humans=200,000 years
Insects=350 million years
100,000 different species live in North America
Insect Classification
Hierarchal system of classification
Kingdom > Phylum > Class > Order > Family
> Genus > Species
Kingdom=Animal
Phylum=Arthropods
Class=Insecta
Arthropoda classes
Crustacea
Crayfish, sowbugs
2 body segments and 5 pairs of legs
Arachnida
Spiders, ticks, and mites
2 body segments and 4 pairs of legs
Symphyla
Symphylans
2 body segments and 12 pairs of
legs
Arthropods
Segmented body
Paired appendages
Bilateral symmetry
Chitinous exoskeleton
Tubular alimentary system, with mouth & anus
Open circulatory system
Nervous system
Respiration by gills, trachea, or spiracles
Sexes are almost always separate
Insecta
Bugs, beetles, and butterflies
3 body segments and 3 pairs of legs
Insect Orders
About 28 different orders of insects
Divided into these orders based on structure of wings and
mouthparts and their type of metamorphosis
Ametabolous: growth without change
Paurometabolous: incomplete or gradual
Hemimetabolous
Holometabolous: complete metamorphosis
Ametabolous
Holometabolous
Paurometabolous
Hemimetabolous
Collembola
Springtails
Ametabolous
Orthoptera
Grasshoppers, crickets
Paurometabolous
Isoptera
Termites
Paurometabolous
Hemiptera
True bugs
paurometabolous
Homoptera
Aphids, scales
Paurometabolous
Coleoptera
Beetles, weevils
Holometabolous
Lepidoptera
Butterflies & moths
Holometabolous
Hymenoptera
Wasps , bees, ants
holometabolous
Diptera
Flies
Holometabolous
Siphonoptera
Fleas
Holometabolous
Dermaptera
Earwigs
Paurometabolous
Thysanura
Silverfish
ametabolous
Ephemeroptera
Mayflies
Hemimetabolous
Odonata
Dragonflies & damselflies
Hemimetabolous
Blattaria
Cockroaches
Paurometabolous
Phasmida
Walking sticks
Paurometabolous
Mantodea
Mantids
Paurometabolous
Phthiraptera
Lice
Paurometabolous
Thysanoptera
Thrips
Hybrid between holo- and
pauro-metabolous
Neuroptera
Lacewings, antlions
Holometabolous
Morphology
Head: Antennae
Filiform: threadlike, the segments are nearly uniform in size and
usually cylindrical (ground beetle)
Monofiliform: like a string of beads, segments are similar in size
and more or less spherical in shape (some beetles)
Clavate: segments increasing in diameter distally (ladybird
beetles)
Serrate: sawlike, segments more or less triangular (click beetle)
Pectinate: comblike, most segments with long, slender, lateral
processes (some beetles)
Setaceous: bristlelike, segments becoming more slender distally
(dragonfly, damselfly)
Plumose: feathery, most segments with whorls of long hair
(math moths; allows for more surface area to pick up
pheromones; mosquitoes)
Aristate: last segment usually enlarged and bearing a
conspicuous dorsal bristal (blow flies; used as air speed
indicators)
(Blow flies) (June Beetle) (Click beetle) (Cedar beetle) (Bark beetles)
(Chalcid) (Mosquitoes) (Fire-colored Beetle)
(Dragonfly) (Snipe fly) (Ladybird Beetle)
Butterfly
Fire-colored beetle
Mosquito Moth
Head: Mouthparts
Chewing
Rasping-sucking: Thrips
Piercing-sucking: cicadas and
mosquitoes
Sponging: houseflies (lap up
liquids)
Siphoning: butterflies & moths
Chewing-lapping: bees (have both
mandibles and a proboscis)
Vestigial: mayflies
Thorax
Prothorax, mesothorax, and metathorax
Each segment bears a pair of legs
Wings are attached to the mesothorax and metathorax, but never
the prothorax
Legs of insects vary greatly in size and form and are often used
for classification purposes
Walking, jumping, diggings, grasping, feeling, swimming,
carrying loads, building nests, and cleaning
Leg adaptations
Grasshoppers: enlarged femur for jumping
Beetle: enlongated tarsi for running
Wings
Are the outgrowths of the body wall
Venation can vary dramatically from species to species and is often
used as a means for identification
Most of insect orders end with “ptera”, which is greek for “with
wings”
Can be covered with fine hairs or scales (moths & butterflies) or
bare (dragonflies)
Abdomen
May have 11 or 12 segments, but often hard to
distinguish from one another
Some may have cerci at the tip of the abdomen
(earwigs)
Length can vary greatly from different insect
species
Development
Critical development occurs just after birth or egg hatch
Reproduction
Most need to mate in order for eggs to be fertilized
Some are able to reproduce without sperm fertilization
Some can reproduce either way
Insect Orders
Insect Injury
Chewing insects Injury by laying eggs
Chew off portions of plant
Piercing-sucking insects Nest materials
Pierce skin and suck up Remove tissue to use in
plant juices nests
Internal feeders
Gain entrance into plant and Vectors of plant diseases
feed on the inside
Subterranean insects
Attack plant from below the
soil surface
Beneficial insects
Pollinators
Aid in the production of fruits, seeds, vegetables, and flowers
Weed feeders
Improve physical condition of soil and promote fertility by
burrowing
Millipedes, centipedes
Scavengers
Devouring bodies of dead animals and plants
Bury carcasses and dung
Beneficial insects
Predators
Catch and feed on other creatures (prey)
Ground beetles
Lace wings and lady bugs
Parasites
Live on or in the bodies of living organisms (hosts)
Host are usually larger and stronger than the parasites and are not
killed promptly
Parasitic wasps of aphids and hornworms
Questions???
Janet Spencer
Extension Agent, ANR
Isle of Wight County
757-365-6262
jaashle2@vt.edu
