Insects

Class Insecta has more species than any other group of animals. Characteristics of insects – flight (most not all) – this allows insects to move long distances and colonize new areas, the have a life cycle where the young are different from adults in feeding and looks.

What is an Insect? Insects have a segmented body, an exoskeleton, and jointed appendages. Their body is divided into 3 parts – head, thorax, and abdomen. They have 3 pairs of legs attached to the thorax. Most insects have a pair of antennae and a pair of compound eyes, 2 pairs of wings on the thorax, and tracheal tubes for respiration.

Responses to Stimuli Compound eyes are made of many lenses that can detect changes in color and movement. Compound eyes do not give quite as much detail as we see but they can detect movement very well. Insects have chemical receptors for taste and smell on their mouthparts, antennae, and legs. They also have sensory hairs that detects slight movements in air or water. Many insects have well developed ears. The ears can be in weird places like behind the legs in a grasshopper.

Adaptations for Feeding Insects have 3 appendages that are used as mouthparts. These mouthparts can look very differently in different insects. Many insects will produce saliva that has digestive enzymes to help break down food.

Movement and Flight Insects have 3 pairs of legs. They can be used for walking, jumping, or capturing and holding prey. Many insects have spines and hooks on their legs for grasping and defense. Many insects can fly and usually have 2 pairs of wings.

Metamorphosis Metamorphosis is the process of changing shape and form. There are 2 types: incomplete metamorphosis and complete metamorphosis. Incomplete metamorphosis is when the juvenile forms look very similar to the adult. The immature forms are called nymphs. Nymphs will not have some features the adults will, like wings. They molt several times and grow and develop the adult structures. Incomplete metamorphosis has 3 stages – egg, nymph, and adult.

Complete metamorphosis – this is a more dramatic change in body form. These insects hatch as larvae that look completely different from the parent. The larvae will eat continuously and grow quickly. After awhile the larvae will change into a pupa. This is when the larvae changes to an adult. The adult will emerge from the pupa. There are 4 stages of complete metamorphosis: egg, larvae, pupa, adult.

Insects and Humans Many insects have negative effects: termites destroy wood structures, moths eat wool clothing and carpets, bees and wasps sting, desert locusts can cause damage to livestock and crops. Mosquitos are annoying and cause itchy bites. Insects also have good qualities. Ag would be impossible without bees, butterflies, wasps, moths, and flies that pollinate. Insects also produce silk, wax, and honey. In some countries they are a food delicacy.

Insect Communication Insects communicate using sound, visual, chemical, and other types of signals. Usually they communicate to find a mate.

Visual Cues Male fireflies use visual cues to communicate with potential mates. They produce light to flash in a certain way.

Chemical Signals Pheromones are chemical signals that affect behavior or development of another member of the same species. Pheromones can signal an alarm, communicate during courtship or dating, ants use pheromones to stay in a line.

Insect Societies Ants, bees, and termites form societies. A society is a group of closely related organisms that work together to benefit the whole group. Example: leaf cutter ants

Castes Castes are groups of individuals that perform a specific task. Basic castes – reproductive females called queens (lay eggs), reproductive males, and workers. Many insect societies only have 1 queen.

Communication in Societies Insects will use touch, sound, and chemical signals to talk to each other in a society. Honeybees communicate with complex movements and pheromones. They can show the type, quality, direction, and distance of food source by dancing.