Figure;2.9: Grasshopper  
Adaptation of grasshopper to its habitat.  
❖ They have jointed legs for locomotion  
❖ They have antenna for sensitivity  
❖ They tracheal system for gaseous exchange  
❖ They compound eyes for vision.  
Housefly  
Habitat: Decaying matter e.g. toilet  
Economic importance of housefly.  
❖ vector of disease e.g. cholera and sleeping sickness  
❖ Used for biological studies  
❖ Source of food to some organisms e.g. toad, chameleon  
Figure;2.10: Housefly  
Beetle  
Habitat: animal dung – on cow dungs.  
Economic importance beetle:  
❖ Contribute to soil fertility  
❖ Used for biological studies/experiments  
❖ Source of food to some animals e.g. birds  
❖ Agents of pollination.  
Figure;2.11: Beetle  
Bee  
Habitat; Found on beehives  
Economic Importance Bee  
❖ Source of food to some organism  
❖ Agent of pollination  
❖ Can sting and poison  
❖ Increase soil fertility when die  
Figure;2.12: Diagram of bee  
Cockroach  
Habitat: Found on toilets  
Economic importance of cockroach  
❖ Vector diseases such as cholera, plague and dysentery  
❖ Source of food to some organism  
❖ Used in biological studies  
Fig: Structure of a cockroach  
Figure 2.13: diagram of cockroach  
Mosquito  
Habitat: on stagnant water  
Economic importance of mosquito  
❖ Vector of diseases. Example malaria, dengue, elephantiasis  
❖ Used in biological studies  
Figure;2.14: Mosquito  
Butterfly  
Habitat ;found on flowers  
Figure ;2.14: Butterfly  
Advantages of Class Insecta  
❖ Are agents of pollination  
❖ Are source of food for humans  
❖ Insects are scanvegers  
❖ Some commercial products are obtained from insects for example  
honey  
❖ Increase soil fertility  
Disadvantages of Class Insecta  
❖ Vector of diseases  
❖ Can parasitize domestic animals for example lice  
❖ Destroy crops for example locusts  
2. Class Arachnida  
The arachnids represent the second largest group of terrestrial arthropods  
after the insects. The class includes the animals whose bodies are  
organised into two tagmata called cephalothorax or prosoma (fused head  
with thorax) and abdomen (opisthosoma). Most of them are carnivores,  
except the mites, which are herbivores. Members of this class include  
spiders, mites, ticks and scorpions.  
Distinguishing characteristics of Arachnids,  
Distinctive features of class Arachnida Arachnids can be distinguished  
from other members of the phylum Arthropoda by the following features:  
❖ Their bodies are divided into two regions; prosoma and  
opisthosoma, separated by a narrow waist-like constriction.  
❖ They lack antennae; alternatively, they use pedipalps to detect  
external stimuli.  
❖ They lack compound eyes; they only have simple eyes.  
❖ They lack true mouthparts; instead, they have two pairs of  
appendages born from prosoma. One pair, the chelicerae or  
poisonous fangs, is used for killing preys or defending themselves;  
the other pair called pedipalps holds the prey in place when the  
animal injects poison.  
❖ Usually, they have four pairs of walking legs.  
❖ Their respiratory structures are book lungs or book gills or trachea.  
Tick  
Habitat: on animal’s skin such as cow, goat  
Figure;2. 15: tick  
Scorpion  
Habitat: at the corner of houses or caves.  
Economic importance of scorpion:  
❖ Used for biological study  
❖ Can bite and poison other animals  
❖ Source of food to some animals e.g. birds  
Figure;2. 15: Scorpion  
Spider  
Habitat: Under the stones or tree logs  
Economic importance of spider  
❖ Used for biological study  
❖ Can sting and poison other animals  
❖ Source of food to some animals, e.g., birds, lizard  
Figure; 2.16: Spider  
Adaptations of spider to its mode of life  
Spiders live in almost every habitat. They are adapted to different  
environments because:  
❖ They have pairs of chericerae which produce silk for capturing  
preys.  
❖ They have pedipalps for sensation.  
❖ They have four pairs of legs for locomotion.  
❖ The hairy spiders have stings used to paralyse prey and defend  
themselves.  
3. Class Crustacea  
Crustaceans form a large group of arthropods that include familiar animals  
such as crabs, lobsters, prawns, shrimps, barnacles, and crayfish. Most  
crustaceans are marine aquatic animals, other are found in fresh water  
habitats, and a few are terrestrial, for example woodlice (Isopota) found in  
leaf litter.  
Distinctive features of class Crustacea  
Crustacea have distinctive features that make them unique among other  
arthropods as highlighted below:  
❖ They possess two body division, which are cephalothorax (the  
head fused with thorax) and abdomen.  
❖ They have carapace or an exoskeleton hardened with calcium salts  
which acts as a protective shell.  
❖ They have heads bearing two pairs of antennae.  
❖ They have a pair of compound eyes at the ends of movable stalks.  
❖ They have at least three pairs of mouthparts.  
❖ are used for gaseous exchange, which are the outgrowth of the  
body wall or limbs.  
❖ They have variable number of legs, sometimes up to ten legs and  
can be modified for swimming. Unlike other arthopods, the legs  
and other appendages of Crustacea have two branches (they are  
biramous)  
Crab  
Habitat: Water bodies e.g. rivers, lake.  
Economic importance of crab.  
❖ Source of food to man  
❖ Used for economic purpose when sold (source of income)  
❖ Can bite other animals  
❖ Used for biological studies