Insects
Insects have the following features
Bodies are divided into three distinct parts: the head, thorax and abdomen.Three pairs of legs wings and one pair of antennae on the head.Their mouth-parts are external and compound eyes (usually with simple eyes as well).
Success of insects:
The majority of them can fly and escape danger.Large numbers of eggs are laid by a single female increasing the chances of survival.The majority have excellent camouflage making it difficult for predators to detect;Other mimic (to copy) well known poisonous varieties.Insects were the first social obligates (individuals that cannot survive on their own and have to be part of a colony). Today the termites and ants are amongst the most abundant insects on Earth.Due to their metamorphic (changing) life cycle, the young and the adults do not compete for the same food source.The evolution of the compoundeye allows them to see in ultra-violet light waves.The evolutionary adaptation of the mouthparts allows insects to utilise a wide range of food sources…
Ecological importance of insects:
insects help maintain the balance in nature: they fulfill the role of predators and parasites on other animals and plants. Insects a food source for a wide variety of other animals including birds, mammals, amphibians and fish. Bees, wasps and ants are a few of the insects that play an essential role in plant pollination.Insects play an important function in the disposing of waste: the larvae of beetles and flies consume dead and decaying matter: the larvae of horn borer moths feed on horns and hooves which most other animals are unable to digest. Many insects pass on a variety of diseases that help to regulate populations of both flora and fauna.
Hemimetabolic (incomplete): egg, nymph and adult
In this method of reproduction, after the eggs have hatched into nymphs, the nymphs moult their exoskeleton as they grow. Each moult is called an instar. The major changes are the development of wings or from an aquatic to a terrestrial lifestyle. Examples: dragonflies, damselflies, mayflies, aphids, bugs, termites.(F1 cockroaches, praying mantids, earwigs, web-spinners, crickets, locusts, grasshoppers, stick insects, stoneflies, cicadas, booklice, lice and thrips.)…
Termites (Order:Isoptera)
Large fungus-growing termites (L3Macrotermes) mounds are built of soil particles bound together with ‘cement’ that consists of termite excrement and saliva. It is a strong, weatherproof structure capable of keeping out most of the termite’s enemies. A large mound may contain a population equal to that of some large cities (approximately a million individuals).
The inhabitants of the termite mound are of different castes:
workers (infertile males and females);
soldiers (infertile males and females);
alates which are winged fertile males and females (present in the mound spring and summer) and
the king and queen.
The workers and soldiers are stunted in growth and their sexual organs have failed to develop; this allows them to devote their time and attention to labor without the distraction of breeding.
When the queen grows too old and her fertility wanes, the workers kill her by licking her to death: as many workers as can get at her surround her day and night. Gradually she grows thinner and thinner until finally only a shriveled skin is left. This is covered with mound material and hidden from sight. Queen termites may survive for over 45 years under optimal climatic conditions.
The flying termites do not, as a rule, travel very far. They are feeble fliers and easy prey to all kinds of insect eating animals. Birds, frogs, lizards, praying mantids, spiders and many other enemies have a great feast when the wedding flight is on and indeed very few of the fliers that leave the nest survive long enough to burrow underground.
The termites are an important link between dead material and plant nutrients. The termites, with the aid of the fungus break down the cellulose in dead plants.
Flies, midges and mosquitoes (order:Diptera)
Diptera means two-winged. This order is by far the most medically important of all insects: they pass on many diseases such as malaria, sleeping sickness, nagana, anthrax and many more but they are also important flower pollinators and predate on many crop pests.
All mosquitoes breed in water and it is only the female that sucks blood. In many species she requires a feed of blood before she can mature her eggs however, in other species, this is not essential and the female is said to be autogenous (the first batch of eggs can be laid in the absence of a meal of blood while subsequent egg-laying requires the ingestion of blood).
A male mosquito cannot suck blood because his mouthparts are imperfectly developed and they are incapable of piercing the human skin. His food consists of the nectar of flowers and the juices of ripe fruits; food which the female will also take when there is no blood available. The male’s antennae are feathery.
The female injects saliva into the wound and this causes an irritation that produces a little local inflammation. This draws a plentiful blood supply to the spot. It is also the means by which Plasmodium sp. protozoa are introduced by anopheline mosquitoes (the malaria transmitting species).