Insects hail from the largest category of phylum Arthropoda and fall under the class Hexapoda or Insecta. In appearance, insects have a segmented body, jointed legs and exoskeleton. Insects have distinctive features that include three major parts namely the head, the segmented thorax and abdomen where the digestive, respiratory, reproductive and excretory organs are found. The head has the eyes, pair of antennae and mouthparts. The segmented thorax consists of three pairs of legs and two pairs of wings. Insects include a large variety of species such as butterflies, bed bugs, houseflies, mosquitoes and so on. Because insects cater to such a massive population, the life of an insect also varies from species to species. Insects are capable of three types of metamorphosis, namely Ametabolous, Hemimetabolous and Holometabolous. We are going to look into these three development stages in insects in order to get a better understanding.
Let’s look at the life cycle of an insect to get a better understanding.
Life Cycle of Insects
1) The Egg – Stage 1 –
Majority of insects begin their life in fertilized eggs. Egg laying amongst insects depends on the species it belongs to, for example, cockroaches or mantids lay their eggs in a bunch attached together that forms the ootheca or egg packet. Eggs of some grasshoppers survive very dry and hot weather conditions and resume development when they acquire moisture. Aedes, which is a genus of mosquito, lays dried eggs that undergo a state of inactivity or dormancy and hatch when eggs come in contact with water.
2) The Larvae – Stage 2 –
Insect larvae have several distinct ways of hatching. While caterpillar larvae bite their way out of the eggs during the hatching process, the flea larvae slit their egg shells to get out. Some insect eggs have an “escape cap” that usually pops open when the larvae builds pressure inside the egg. After hatching, the space above the base of the antennae known as the Ptilinum breaks down into the body till the cuticle of the insect gets harder. The insect larva undergoes several stages of molting where it sheds old cuticles multiple times to get new cuticles. Insect larvae vary in shape depending on the species, therefore they are divided into five kinds. The caterpillar-like larvae are eruciform, the maggot-like larvae are vermiform, the wire worm-like larvae are elateriform, the grub-like larvae are scarabaeiform and the long, elongated larvae are campodeiform. These larvae then transform into pupa and enter the next stage.
3) The Pupa – Stage 3 –
During this stage, the pupa is mostly resting and inactive. The larval tissues collapse and reorganize the adult form of the pupa. After this process is over, the pupa molts and emerges out as an adult with a pair of wings. In the pupa stage, the wings develop into its complete form and the adult insect enters the world.
4) The Adult – Stage 4 –
Adult insects have tactile hair, which is found on the antennae, legs, torsal regions of the body, and helps in signaling the insect to its external environment. Tactile hair covers the entire surface of an insect. In this stage, the adult insect is sexually mature and spends its time mostly reproducing. The mating in adult insects vary depending upon the species. For example in butterflies, the female butterfly attracts the male butterfly by flying and showing her bright colored wings. Similarly in mayflies, the male mayflies gather in swarms to lure the female mayflies.
Insects are capable of surviving in any environment. They live on land, water and air, and are found in every nook and corner of the world. As of today, insect species comprise 10 quintillion insects all over the world. Insects are very vital to the ecosystem of the world as they help in pollination of plants, decomposition of plants and animal parts. Insects themselves are a food source for many organisms.
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Frequently Asked Questions on Insect Life Cycle
What is entomophagy?
Entomophagy is the practise of eating insects like tarantulas and centipedes. The egg, larvae, pupa and adult form of insects are largely consumed by humans even today.
What are holometabolous insects?
Holometabolous insects undergo complete metamorphosis with four life stages namely egg, larvae, pupa and adult stage. Butterflies, ants, wasps are holometabolous insects.
What are hemimetabolous insects?
Hemimetabolous insects undergo incomplete metamorphosis, which includes three life stages namely egg, the nymph and the adult stage. The nymphs undergo incomplete metamorphosis resembling the adult insects. The difference between nymphs and adults is that nymph insects lack reproductive organs and functional wings.