Entomology

Entomology is the study of insects. It is a major branch of animal zoology. Insects are one of the most successful and diverse groups of living organisms in the world today. Approximately 1.5 million species of insects have been identified by scientists as of the end of the twentieth century. However, it is estimated there may be as many as twice that number on Earth. The number of insect species is greater than the number of all other species of organisms combined. It is estimated that there are about 200 million insects for every living human. Insects are members of the kingdom Animalia, the phylum Arthropoda, and the class Insecta. Insects share the major group Arthropoda with creatures such as crabs, lobsters, shrimp, spiders, scorpions, ticks, mites, centipedes, and millipedes. Common insects include ants, butterflies, bees, cockroaches, beetles, flies, grasshoppers, mosquitoes, dragonflies, moths, wasps, and termites.

Insects have a tough exoskeleton (external skeleton) and three pairs of walking legs. The majority of insects have wings, and those with wings have two pairs, except flies, which have only one pair. Their bodies are divided into three regions: the head, thorax, and abdomen. All insects hatch from an egg in a form which is different from that of the adult insect. A well-known example of this is the caterpillar (the larval stage) and butterfly (the adult stage). Insects are characterized by their small sizes and short lifespans.

Scientists believe that insects have inhabited Earth for about 380 million years. They occupy nearly every type of environment except for salt water. They are most numerous in tropical climates and on land. Their enormous success is believed to be due to three main factors: their exoskeleton, size, and diet. Their tough exoskeleton protects them against physical damage and water loss. Their small size allows them to occupy many small areas unavailable to larger animals. Small size also allows for a faster reproductive rate. Finally, insects eat almost anything and everything.

Insects play many important roles in nature. Insects such as bees, butterflies, moths, and flies pollinate flowering plants. Many insects aid in the decomposition process and nutrient cycling, or exchange. Insects are important food sources for other animals, such as birds, and also eat other insects, thus keeping insect populations in control.

Most entomologists work in the field of economic entomology, which is also called applied entomology. They study the small minority of insects that are harmful to humans. Harmful insects include those that destroy crops and buildings and those that transmit diseases to humans. Insects that feed on plants such as grasshoppers destroy plant crops and timber. Other insects transmit plant diseases. Insects such as termites destroy wood buildings. Bloodsucking insects such as mosquitoes, lice, and fleas transmit some of the most serious infectious diseases in the world. These include malaria, dengue fever, yellow fever, bubonic plague, and typhus.

Scientists attempt to reduce the number of insect pests through a variety of ways. Cultural controls include the draining of swamps where mosquitoes breed. Chemical controls include the use of pesticides and insect repellants. Biological controls include the use of animals that naturally prey on insect pests.

People are also inadvertently decreasing the number of insects by destroying their natural habitats. Destruction of natural areas by human activities is wiping out species of insects that we will never even know existed. What wondrous creatures are we missing?