® EXTENSION Know how. Know now. EC1588 Introduction to Entomology James A. Kalisch, Entomology Extension Associate Ivy Orellana, Extension Assistant Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture. University of Nebraska–Lincoln Extension educational programs abide with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department of Agriculture. © 2014, The Board of Regents of the University of Nebraska on behalf of the University of Nebraska–Lincoln Extension. All rights reserved. Introduction to Entomology James A. Kalisch, Entomology Extension Associate Ivy Orellana, Extension Assistant Insects and mites are among the known to exist. They have three the insects . Within the class Insecta, most numerous animals on earth. In a characteristics in common — a seg- various characteristics are used to typical midsummer landscape and gar- mented body, jointed legs, and an group insects into orders (Table 1). den, there are approximately a thou- exoskeleton. The Arthropoda phylum These characteristics are easily visible sand insects in addition to mites and is divided into classes, and some com- and do not require a microscope; for spiders! The goals of this publication is mon names of each class includes example, mouthparts, wings, and type to introduce the science of entomology the crustaceans, centipedes, milli- of metamorphosis are all identifying and insect identification to those who pedes, spiders, ticks and mites, and characteristics. are active in outdoor landscapes or natural settings. Insects play a valuable role in our Table 1. The following table describes the common names associated with natural world. For example: each insect order. • Bees and some species of flies pol- Blattodea Cockroaches linate most fruits and vegetables. Coleoptera Beetles and Weevils • Many insects are sources of food Collembola Springtails for birds, fishes, reptiles, amphib- Dermaptera Earwigs ians and spiders. Diplura Diplurans • Some insects produce useful prod- Diptera Flies, Mosquitoes, Gnats, Midges ucts such as honey, wax, shellac, Embioptera Webspinners and silk. Ephemeroptera Mayflies • A large number are decomposers Hemiptera True Bugs, Scale Insects, Aphids, Leafhoppers that help maintain nutrient cycles Hymenoptera Ants, Bees, Wasps in the environment. Isoptera Termites • Other insects are considered ben- Lepidoptera Butterflies, Moths eficial as predators and parasites, Mantodea Mantids by feeding upon insects or mites Mecoptera Scorpionflies considered to be pests. Megaloptera Alderflies, Dobsonflies, Fishflies Even though relatively few types Neuroptera Lacewings, Antlions, Mantispids, Dustywings of insects are pests, they are the ones Odonata Dragonflies, Damselflies most often talked about. Some insects Orthoptera Grasshoppers, Crickets, Katydids such as aphids, leafhoppers, and thrips spread plant diseases. Insects such as Phthiraptera Sucking and chewing lice mosquitoes and midges may spread Plecoptera Stoneflies deadly or debilitating diseases to Psocoptera Booklice, Barklice humans , livestock, and wildlife. Raphidioptera Snakeflies Siphonaptera Fleas Basics of Classification Thysanoptera Thrips Thysanura Silverfish, Bristletails Trichoptera Caddisflies Arthropods represent more than Zoraptera Zorapterans three-fourths of the animal species © The Board of Regents of the University of Nebraska. All rights reserved. 3 Figure 1. Grasshopper body parts and regions. Since there are numerous insect of three parts (head, thorax, and • Legs. An important classification species, and because many of them abdomen) and is supported by a characteristic of insects is the pres- are small and seldom encountered, hard body wall, the exoskeleton ence of three pairs of jointed legs. relatively few species have common (Figure 1). The exoskeleton has Almost all adult insects have legs, names. Those that do are either partic- a flexible, top layer known as the and some immatures do not have ularly showy insects, such as the luna cuticle, which contains a layer of wax legs, but will as adults. An insect’s moth and the tiger swallowtail, or they and helps to prevent desiccation. legs are adapted according to how are economically important species, The exoskeleton of an immature the insect lives and behaves (Figure like the honey bee and the dreaded insect is not usually as hard as that 2). For example, if an insect hops Colorado potato beetle. of the adults, because the cuticle is a lot to avoid predators, then the not fully formed. femur is greatly enlarged, as is the Insect Morphology case with grasshoppers. Thus, legs The thorax, located between the vary in size and shape because they head and abdomen, is made up of can be used for walking, jumping, Insects possess the following char- three segments: prothorax, meso- digging, grasping, feeling, swim- acteristics: three body regions; three thorax, and metathorax. Each ming, holding objects, building pairs of legs; one pair of antennae; and segment has one pair of legs. In structures, and cleaning parts of the none, one, or two pairs of wings. Legs addition, the mesothorax and meta- body. One important leg adapta- and other appendages are often greatly thorax each may bear one pair of tion in larvae is prolegs. Prolegs, or modified to suit the insect’s habit and wings. Some insects, such as beetles false legs, are fleshy body projections environment. and grasshoppers, have a thickened, with rows of tiny hooks, helping the protective pair of wings. The abdo- insect cling to surfaces and plants. men contains several segments, each They also provide additional sup- Insect Body joined by a flexible membrane so port in locomotion. it can expand and contract to aid with respiration. Some insects have • Wings. Venation, or arrangement • Head, thorax, and abdomen. The tail-like appendages at the end of the of veins in the wings, is different adult insect’s body is made up abdomen, referred to as cerci. for each species of insect; thus, it 4 © The Board of Regents of the University of Nebraska. All rights reserved. Cursorial (running) Fossorial (digging) Saltatorial (jumping) Raptorial (catching and holding) Natatorial (swimming) Figure 2. The five types of insect legs. Scaly — flattened scales with hair Elytra — hard protective cover wings Hemelytra — half leathery and half membraneous Membranous — transparent Tegmina — leathery Halteres — club-like Figure 3. The six types of insect wings. © The Board of Regents of the University of Nebraska. All rights reserved. 5 Geniculate Plumose Pectinate Serrate Clavate Filiform (elbowed) (feathery) (comb-like) (saw-toothed) (gradual club) (thread-like) Aristate Setaceous Moniliform Lamellate Capitate (bristle-like) (bristle-like) (bead-like) (finger-like) (clubbed) Figure 4. The various types of insect antennae. serves as a means of identification that vary greatly in form and com- mouth, which is composed of man- (Figure 3). Many insect orders end plexity (Figure 4). They are primarily dibles and its extendable tongue. in “ptera,” which comes from the organs of smell, but can serve other These components work together to Greek word meaning “wing.” For functions such as sensing humidity help the bee chew, mold wax, suck instance, Hemiptera means “half- levels, sound, flight air speed, taste, up nectar, and regurgitate fluids to winged,” Hymenoptera means direction, and touch. feed the young (brood), etc. Siphon- “membrane-winged,” and Diptera ing mouthparts are common with means “two-winged.” Most imma- • Mouthparts. The most remarkable butterflies and moths. No mandibles ture insects do not have wings, but and complicated structural feature are present, only a long, flexible some have wing pads that enlarge of insects is the mouth. Just like in- tube used to insert into flowers to as the insect grows toward adult- sect legs, mouthparts vary in form extract nectar. Piercing-sucking hood. One wing modification of flies and function, based on where and mouthparts occur with true bugs, is the presence of halteres, which how an insect lives and what it feeds aphids, and mosquitoes. This type are small, knobbed structures that upon (Figure 5). Each type of mouth of mouthpart is sharp at the tip and replace the hind pair of wings and is made up of several basic, common is inserted into plants or animals to aid in balance. structures, but some may be greatly withdraw nutrients. reduced while others are enlarged. • Antennae. The antennae are a prom- Chewing mouthparts, which consist In some cases, insects of the same inent and distinctive feature of most of mandibles and other parts, work order will always have the same insects, and a pair is always present together to hold/pinch, maneuver, mouthparts for each life stage, as on the adult’s head. Antennae are chew, and deliver chewed food to the with grasshoppers. Others will have located between or in front of the mouth. An example of a chewing- different mouthparts in different life eyes and are segmented structures lapping mouthpart is the honeybee’s stages. For example, the monarch 6 © The Board of Regents of the University of Nebraska. All rights reserved. Siphoning Sponging Chewing-Lapping Piercing-Sucking Chewing Figure 5. The five types of insect mouthparts. caterpillar has chewing mouthparts, Most insects do not grow gradu- There are three types of meta- but the adult monarch butterfly has ally over their lifespan, as many