EarthWorks Orchard Curriculum
Background Information: Insects
What are insects? Insects are animals that belong to the class Insecta. Unifying characteristics of insects are that they have six legs, three body segments (head, abdomen, thorax), compound eyes, two antennae, and are invertebrates. Instead of having an inner skeleton of bones, mature insects have a hard outer skin, or exoskeleton, made of chitin. Scientifically speaking, spiders, daddy-long-legs, mites, centipedes and millipedes are not insects.
All insects lay eggs and go through a physical process of transformation called metamorphosis. Some insects go through complete metamorphosis (a four-step process) and others go through incomplete or gradual metamorphosis. An insect undergoing complete metamorphosis start as an egg, hatches into a larva, becomes an inactive pupa, and then after a complete transformation, emerges as an adult. An insect undergoing incomplete or gradual metamorphosis starts as an egg that hatches into a nymph, and after several small changes, becomes a full grown adult.
Some insects that go through each process are:
Complete metamorphosis: Moth, Butterfly, Bee, Wasp, Fly, Ant, Beetle
Incomplete metamorphosis: Dragonfly, Damselfly, Mayfly, Grasshopper, Cicada, Aphid, and Cockroach
Good Bug, Bad Bug:
Insects in the orchard can be harmful or beneficial. "Harmful"
insects or "pests" harm the plants we grow. They usually do this by eating some part of the plant as food to survive. They may also make their home/nest in a plant, debilitating its functionality in part or completely.
Beneficial insects may include parasites, predators, and pollinators. Parasites can be helpful in an orchard if they live off of pests and eventually their host pest dies (parasitic wasp, for example). Predators hunt and eat pests. Pollinators transfer pollen from one flower to another. Without pollinators, fruit trees wouldn't produce fruit (nor would gardens produce any tomatoes, squash, peas, watermelons, peppers, etc). Even pests are essential in the overall picture; without pests, predators and parasites couldn't survive. Really there are no "bad bugs;" there are insects that help and insects that feed the insects that help.
For more information on parasites, listen to the following stories on RadioLab
http://www.radiolab.org/2009/sep/07/
Worms v Insects:
While worms and insects can look virtually interchangeable at some points in their development, worms will never go through a metamorphosis (complete or incomplete), do not have the same body segments, legs, or any other key elements of the class Insecta. The following image (of Drosophila melanogaster, the fruit fly) demonstrates one key difference between worms and insect larvae: insect larvae segments are correlated directly to particular body segments. Worm segments are almost entirely uniform, except for the head, clitellum, and tail.
Created by EarthWorks Projects, Inc.
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