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What is an Insect?

Before we go exploring it might be a good idea to know exactly what an insect is.

  • An insect is defined as an animal that has 3 body segments (head, thorax, and abdomen), 6 legs, and two antennae.

Are insects the same as spiders?

  • Insects, spiders, centipedes, millipedes, and crustaceans (lobsters, shrimp, crabs) all belong to the same group (Phylum) called arthropods.
    • However, they are in different subgroups (Subphylums). This is shown below in figure 1.
      • Insects, millipedes, and centipedes, are in the Subphylum Uniramia.
      • Crabs, crayfish, and pillbugs, are in the Subphylum Crustacea.
      • Spiders, scorpions, ticks, and horseshoe crabs, are in the Subphylum Chelicerata.
 
Figure 1. Arthropoda phylogenic tree (Graphic from biologycorner.com)

What are the differences between insects, spiders, centipedes, millipedes, and crustaceans?

  • Insects have 3 body segments (head, thorax, and abdomen), 6 legs, and two antennae. (Class: Insecta)
  • Spiders have two body segments, eight legs, and lack both antennae and wings. (Class: Arachnida)
  • Centipedes have numerous body segments with 1 pair of legs on each segment, and antennae. (Class: Chilopoda)
  • Millipedes have numerous body segments with 2 pairs of legs on each segment, and antennae. (Class: Diplopoda)
  • Crustaceans have three body segments, more than eight legs, and antennae.
Figure 2. Basic characteristics of insects
Figure 3. Basic characteristics of spiders

What do insects do?

Insects do a lot more than most people realize and impact our lives in many different ways.

  • Pollinators, like bees, butterflies, moths, and beetles, pollinate our farmers crops which provides us the food we eat. Some experts say that one third of every food and beverage we consume is available to us because of insect pollinators.
  • Without insects human and animal waste would be piled high all around us. Decomposers are insects that help to get rid of dead organic material, such as dead plants and animals. Some examples of decomposer insects are dung beetles, cockroaches, and termites.
  • Insects can be found in the field of medicine as well. Some insects, such as mosquitoes and biting flies, are able to spread illnesses to humans and animals. There are also medically helpful insects, such as the larvae of the green bottle fly, which can be used to help keep wounds clean and aid in healing.
  • There also insects that help control other insect pests. For example, lady beetles (lady bugs) feed on aphids which are insects that harm some plants. This type of interaction is often referred to as biological control.
  • Many products come from insects. For example, silk comes from silkworms, honey comes from honey bees, and red food coloring is created from cochineal scale insects.

 

Life Cycle

There are three different types of development that insects can go through and every insect goes through one of these to reach maturity.

The three types of development are…

  • Ametabolous (slight or no metamorphosis) 
    • Development in which the insect hatches and gradually increase in size until they reach adulthood.
    • Few insects go through this type of development, examples are springtails and silverfish.
  • Hemimetabolous (incomplete metamorphosis)
    • Development in which an insect goes through 3 distinct stages.
      • egg → nymph → adult
      • Immature usually resembles adult, gradually develops wing pads.
    • Some insects that go through this type of development are grasshoppers, praying mantises, cockroaches, and dragonflies.
  • Holometabolous (complete metamorphosis)
    • Development in which an insect goes through 4 distinct stages.
      • egg → larva → pupa → adult
    • Some insects that go through this type of development are butterflies, moths, bees, and ants.
The 3 types of development

Now that you know the basics lets go exploring!

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