INSECTS

Introduction

• Insects have for a long time been known as pollinators, honey

producers, vectors, food and for beauty.

• Insect populations and their variety can tell us how important

they are to the environment.

• Their physical features and behavior give an idea of the role

they play in the lives of man, plants and other living organisms.
•Look at the organisms in the picture. Are they
all insects? Give reasons.
•Can you identify some of the common insects
we interact with in our environment?
•Do you remember the phylum and class to
which they belong?
External Features of an Insect
• All insects have a head, thorax and abdomen. These parts bear
other structures that enable the insect to function normally and
live well in its environment
• Activity 4.1: Observing and drawing the back (dorsal) view
of a cockroach

• What you need

• i) Freshly killed adult cockroach

• ii) Notebook

• iii) Pencil

• NB: You can search for an adult cockroach in environment.

• What to do
• Place (on a white background) the cockroach on its legs with
the head away from you (dorsal view).

• Pull all the wings upwards and outwards. (Do not pluck them
off).

• Draw the structure of the whole cockroach.

• Label the following parts: hind wing, leg, thorax, head, fore
wing, abdomen, compound eye and antennae.
Dorsal View Ventral view
• The Head of an Insect
• The head of an insect bears antennae, mouth parts suited to
the type of food the insect feeds on and may or may not have
eyes.

• If the insect has eyes they are either simple or compound.

• Activity 4.2: Identifying the features on the head of an
insect
• What you need
• i) Hand lens
• ii) Freshly killed adult cockroach, housefly, mosquito, worker
• bee, butterfly and termite
• iii) Notebook

• NB: Try to find these insects from your environment and look at
them practically if possible
• What to do

• Observe the features of the antennae, eyes and mouth parts of

the insects provided.

• Describe the features in the table below.

Insect Description

Antennae Eyes Mouth parts

Mosquito

Termite

Butterfly

Housefly
QUESTIONS
• 1. (a) What is the function of antennae to an insect?

(b) Among the insects provided, which do you think has antennae that
are specifically adapted to its way of life? Give reasons for your answer.

• 2. Did all the insects have eyes? If no, which insect did not have eyes?
• 3. Based on your observations, select the insects which have the
following types of mouth parts and give a reason f or your answer.

• a. Biting-chewing mouth parts

Reason
• b. Piercing-sucking mouth parts
Reason
• c. Siphoning mouth parts
Reason
• d. Sponging mouth parts
Reason
Assignment
• For the remaining insects, complete the table for the descriptions of
the features of the head
• The Thorax of an Insect
The thorax of an insect bears its legs and may or may not have
wings.
Activity 4.3: Identifying the features on the thorax of an
insect
• What you need
i) Hand lens
ii) Freshly killed adult cockroach, housefly, mosquito, worker
bee, butterfly and termite
iii) Notebook
What to do
• Using a hand lens observe the features of the thorax of the
insects provided.
• Describe the features in the table below.
Insect Description
Wings Legs

Mosquito

Termite

Housefly

Honey bee

Butterfly

Cockroach
Questions

1. What are the legs and wings in insects used for?

2. Did all the insects have wings? If no, which one(s) did not have

3. Was there an insect(s) with more than one pair of wings? If yes,
which one(s) was it? Suggest the functions of the wings observed.

4. (a) Which insects have special features on their legs?

(b) What are those features and what are they used for?
Dichotomous Keys
A dichotomous key is a tool that can be used to identify organisms in the
natural world. Dichotomous originates from the Greek meaning “cut in
two”. Each step of the key provides two choices until there are no more
choices to be made and you have identified the organism.
• Example of a dichotomous key
• First determine the number of couplets = (n-1) where n is the number of
organisms e.g. for 4 specimens, number of couplets/steps would be (4-1)
• A dichotomous key to identify insects (cockroach, Termite, Housefly and
bee)
1 a) has long antenna………….cockroach
b)has short antenna………….go to 2
2 a) has no eyes……………………. Termite
b) has eyes……………………… go to 3
3. a) has no mandibles……………..housefly
b) has mandibles…………………worker bee
Activity 4.4 Constructing a dichotomous
Task
• Use your knowledge from making flow charts to construct a
dichotomous key for any four of the insects provided using the
characteristics/features identified in activities 4.2 and 4.3 above
Habits and Habitats of Some Common Insects
Cockroaches
• live in damp but warm places and are
generally found in kitchens and
cupboards.
• They are nocturnal animals hiding in
holes and crevices during the day
and coming out at night.
• They feed on plant and animal
material.
Houseflies
• live in warm places and are generally
found everywhere around the homes.
• Houseflies breed in manure and
decomposing material.
• They are seen flying around during the
day and hiding away at night.
• They feed on anything whether plant or
animal material and your food left
uncovered.
Mosquitoes

• live in dark and cool places.

• The eggs, larvae and pupa are found in

ponds, slow flowing water or in stagnant
water in tins and broken bottles.

• They are nocturnal animals hiding in

dark places during the day and coming
out at dusk.
Honey bees

• live in various types of hives.

• They are social insects, exist in

different castes i.e. …….

• Fly around during the day from one

flower to another and at water points.

• When the sun goes down, they retire

to their hives.

• They feed on nectar & pollen from

flowers
Termites

• live in damp but warm

termite mounds.

• They are social insects

living in colonies

• They exist in 4 castes i.e.

……..

• They feed on fresh and

dry plant material.
Butterflies

• live in various areas.

• Fly around during the day

from one flower to another
and at water points.

• When the sun goes down,

they also hide in trees.

• They feed on nectar from

virtually every flower
available.
The Beneficial and Harmful Aspects of Insects

• Insects have an important role they play for the existence of the
rest of the organisms.

• This role may be positive/beneficial or it might be

negative/harmful to the organism.

Activity: Complete the table below

Note: Put into consideration the different stages of the lifecycles of

these insects.
Insect How it is helpful How it is harmful

Cockroach

Housefly

Mosquito

Honey bee

Butterfly

Termite
Methods of control
You have already found out that some of the insects are pests.
What is a Pest?
• There are a number of ways we can control pests. These include:
• Cultural control i.e modifying gardening practices (crop rotation,
sanitation, trap cropping, time of planting, draining stagnant water)
• Physical Control i.e modify physical factors in the environment (flaming,
flooding, cold storage, ionizing, radiation, light traps etc)
• Mechanical control i.e directly remove or kill the pests or put barriers to
keep pests away (sticky bands, hand nets, swatting, shaking plants, ant
pans, bagging fruits, trenching etc)
• Biological Control i.e use of natural enemies
• Chemical control ie use of chemicals to kill pests, inhibit feeding or mating
(repellants, confusants &irritants)
• Integrated pest Management(IPM) ie blending all effective, economical
and environmentally sound control methods
• Activity 4.6: Finding out the methods of control of the harmful
stages of insects
• What to do
• Brainstorm:
• i) the harmful (pest) stage in the life cycle of a cockroach ,housefly,
mosquito, butterfly and termite.
• ii) the methods that are used to control the cockroach, housefly,
mosquito, butterfly and termite in your environment.
• For each insect, write down your discussion in form of a report
include information on:
• a) the harmful/pest stage of the insect.
• b) control methods that are harmful to the environment and those
that are not harmful to the environment.
• Activity 4.7: To create an insect trap
• What you need
• i) markers
• ii) charts/manila paper
• iii) locally available materials
• What to do
• For any one of the insects you have studied, that is, a pest,
design and make a trap using locally available materials.
 Activity of Integration

The following is an extract from a media brief on control of the Fall

Armyworm in Uganda by the Minister for Agriculture, Animal
Industry and Fisheries. Read the extract and answer the questions
that follow.
As a result of the climate change and climate variability, Uganda is
experiencing an outbreak of new pests and diseases such as the coffee
twig borer, banana bacterial wilt, cassava brown streak disease, tomato
leaf miner, maize lethal necrosis and now the Fall Armyworm. This will
negatively impact the nation’s food and nutrition security and wealth
creation efforts.
In the second season of 2016, the Ministry of Agriculture received reports
of a severe outbreak of “caterpillars” on maize plants in the districts of
Kasese, Kayunga and Bukedea. A visit made to these districts found that
almost 40% of the maize crops in the fields visited were attacked by an
unknown pest. The National Agricultural Research Organization (NARO)
has confirmed identity of the pest as a moth commonly known as the Fall
Army Worm.
The fall army worm is native to tropical and subtropical regions of the
Americas. How it arrived in Africa is not clear. There is suspicion, however, that
the pest could have been introduced as a result of increase in trade (imports)
of Agricultural commodities across continents and the pest’s migratory nature
of 2000km per annum could have facilitated its entry into Uganda.
First observed in Nigeria in January 2016, the pest is now reported in several
other countries including Togo, Ghana, Zambia, Zimbabwe, South Africa,
Malawi, Mozambique, Namibia and Kenya. In Uganda to date, the pest has
been confirmed in over 54 districts.
The pest is known to feed on more than 80 plant species, including cereals
(maize, millet, sorghum, sugarcane, rice and wheat), legumes (cowpea,
groundnuts and soybean), cotton and many pasture grasses (Rhodes grass,
Kikuyu grass, Lucerne and other pasture grasses).
The destructive stage of the pest is the caterpillar. The caterpillar feeds
aggressively on most parts of the plant including the leaves, stems of maize,
sorghum, rice, Kikuyu grass, Napia grass and sugarcane crops. This feeding
damage results in a reduction in both yield and grain quality.
The adult moths move in large swarms at night with each female laying up to
2000 eggs and the emerging caterpillars are aggressive feeders with the
potential to destroy a hectare within 72 hours in its later stages. The moths
are strong flyers, when the wind conditions are right; they are capable of
covering over 2000 km per year.
Tasks:
1. Suggest, giving reasons, whether the fall armyworm is an insect or not.
2. Apart from man, write down four other organisms that are affected by the
destruction of crops due to the fall armyworm. Give a reason for your
answer.
3. Write down four explanations why the fall armyworm is a hard/difficult
pest to control.