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As previously stated in Section 3, “A good inspection and correct identification result in knowledge of the pest, its biology and behavior, and solution of the pest problem.” This section is designed to assist in the identification of common structural pests and to provide information on their basic biology, habits and control. TAXONOMIC CLASSIFICATION All living things are classified using a binomial system, i.e., they ore named according to their genus and species. The method of classifying plants and animals is described below with the divisions listed in order of increasing specificity. Kingdom (Animal) — This major division includes most living organ isms which are capable of motion and do not have chlorophyll in contrast to the plant kingdom which includes most living organisms which are immobile and contain chlorophyll. Phylum (Arthropoda) — This is the first major taxonomic unit that includes animals which share fundamental patterns, organization, and de scent. Arthropods are characterized as having jointed appendages, an exoskeleton, dorsal heart, ventral nervous system, and cold blood. Class — There are many classes in each phylum; these classes are further subdivided into orders. The five major arthropod classes are arachnid, chilopoda, crustacean, diplopoda, and hexapoda. Order—Classes are subdivided into orders—groups of living things with major common characteristics such as number and types of wings, types of legs and mouthparts, and type of development. Family — Orders are subdivided into families which describe groups of animals with a wider range of common characteristics. Most family names ore recognized by their suffix “-idoe.” The ability to identify a pest to family often provides sufficient information so that a pest management program can be implemented. Genus — Once identification reaches this point, sufficient information exists on biology, habits, and control for the problem to be effectively managed. The name of the genus is always capitalized and italicized or underlined. Species — The lost major subdivision in the classification scheme, species describes a distinct group of life forms which has well-defined characteristics in common and is capable of producing offspring with the same characteristics. It is helpful to be able to identify pests to species because it provides more specific information on their biology, habits, and control. The name of the species is always in lower case and italicized or underlined. The following are examples of how two of the most common structural pests are classified:
When reference is made to a species, both the genus and species is given, e.g., German cockroach (Blattella germanica) and house mouse (Mus musculus). INSECT GROWTH AND DEVELOPMENT Insects hatch from eggs and progress through several stages (instars) before reaching the adult and reproductive stage. The growth of the insect is limited by the size of the exoskeleton; in order to grow, the exoskeleton must split, thus, allowing the more mature developmental stage to crawl out and form a larger exoskeleton. During this process, the immature insect appears white (this often generates reports of albino insects), but as the exoskeleton hardens, it becomes darker. Once an insect reaches the adult stage, it is unable to grow any larger. Thus, there are no such things as “baby” flies; the flies are simply smaller due to environmental and food conditions during their growth and development process. Metamorphosis is the process by which insects grow and change in form from the egg to the adult. As they progress through these developmental stages, they molt several-to-many times depending on the species; each molt results in an instar. The instars are numbered according to the number of molts through which the immature insect has gone. The development time from egg to adult can be as short as a week to as long as seventeen years for the periodical cicada. The two common types of metamorphosis are simple and complete. Simple metamorphosis involves a gradual change, i.e., the immature insect looks more and more like the adult with each successive molt. In insects with wings, external wing pads develop during the early instars; compound eyes, if present in the adult, are developed in the early instars, and there is no inactive stage prior to adult emergence. pct-34.jpg Simple insect metamorphosis. Complete insect metamorphosis. The immature insects are called nymphs (i.e., terrestrial species) and naiads (i.e., aquatic species). Pest management of insects with this type of development is simpler because the nymphs and adults have similar appearance, biologies, and habits; there fore, the control strategies are basically the same. Common structural pests which undergo simple metamorphosis include cockroaches, crickets, lice, earwigs, and sowbugs. Complete metamorphosis involves four developmental stages — egg, larva, pupa and adult, none of which resemble each other during development. In this type of development, the wings develop internally, compound eyes are not present in the larval stage, and there is a prolonged of inactivity (pupal stage) prior to adult emergence. Insects which undergo complete metamorphosis pose a greater pest management challenge because the larvae and adults do not look alike, they have different biological characteristics and habits, they often cause different types of damage, and the pupal stage is resistant to most pest management strategies. Thus, these species of insects are generally more difficult to control and may require several pest management strategies. Common structural pests undergoing complete metamorphosis include ants, bees, wasps, flies, fleas, beetles, and moths. INSECT STRUCTUREThis section describes the major anatomical features of the three insect body regions (head, thorax, and abdomen) which are often used for identification. pct-35.jpg An insect is made up of three primary body regions: head, thorax and abdomen. An insect’s antennae are its major sense organs for touching, smelling, and hearing. Insect Head Antennae — The antennae are the major sense (i.e., touch, smell, and hearing) organs found on the head. They are of various forms and shapes, e.g., filiform — thread-like (e.g., cockroach), moniiliform — bead-like (e.g. some bark beetles), serrate — saw-like (e.g., drugstore beetle), clavate — clubbed (e.g., ladybird beetle), and capitate — having a head (e.g., some powder post beetles). Eyes — Most insects hove a pair of large compound eyes composed of many small lenses. Some insects have one-to-three ocelli, i.e., simple eyes, located between the compound eyes. Mouthparts —The mouthparts of most insects are located on the lower part of the head; they project downward, although there are a few species in which the mouthparts project forward. Mouthparts are very useful in insect identification and provide some insight into the type of food eaten by the insect. Six types of mouthparts are commonly described for insects: Chewing mouthparts are the most primitive and basic mouthparts found in insects, e.g., cockroaches, earwigs, crickets, many larvae, beetles, and termites. They are composed of seven segments, two mandibles (i.e., laws), an upper lip (i.e., labrum), a tongue (i.e., hypopharynx), two lower jaws (i.e., maxillae), and a lower lip (i.e., labium). All other types of mouthparts are composed of the same components although they are often modified significantly. Rasping-sucking mouthparts are found in thrips which use them to tear the surface of plant tissues, thus, causing fluids to flow out of the plant. Piercing-sucking mouthparts are usually long and slender and needle-like. They are found in a variety of insects, e.g., mosquitoes, biting flies, fleas, lice, predators, and plant bugs with significant modifications among species. Sponging mouthparts are found in filth flies and fruit flies; they are adapted for sucking up liquefied food. The base of the elongated mouthpart is shaped into a large fleshy sponge which has a series of grooves radiating from the central food channel. Siphoning mouth parts are found in butterflies and moths. The seven elongated mouthpart components are fused to form a long siphoning tube which is used for sucking up plant nectar and water. These mouthparts are coiled up at the base of the head at rest. Chewing-lapping mouthparts are found in some bees and wasps. The structure of these mouth parts allows these insects to chew solids and suck up exposed liquids. Immature insects undergoing simple metamorphosis typically have the same mouthparts as the adults. However, there is more variability in the mouthparts of larvae undergoing complete metamorphosis. For example, moth and butterfly larvae have chewing mouthparts; most beetle adults and larvae have chewing mouthparts; and ant larvae have reduced chewing mouthparts. The Insect Thorax The thorax, the middle section of the insect body, is composed of three segments which, listed from front to rear are heprothorax, mesothorax, and the metathorax. pct-37.jpg A insect legs are always jointed and one pair is attached to each thoracic segment. Legs — Insect legs are always jointed; one pair is attached to each thoracic segment. The leg has six parts — from their attachment to the thorax outward, they are the coxa, trochante femur, tibia, tarsus, and pretarsus. The tarsus is composed of several segments; the pretarsus typically has a pad and one or two claws, legs come in all shapes and sizes and ore modified for a variety of activities, e.g., running, jumping, swimming, digging, and grasping. Legs are used for identification and provide insight into the insect’s biology and habits. Wings — Most insects have two pairs of wings which are outgrowths of the last two thoracic segments. However, some insect species have only one pair of wings; a few have none. On flies, the second pair of wings is modified into balancing organs called halteres. Most insect wings have a cellophane-like appearance and few-to-many veins which often are used for identification. The first pair of wings on most beetles is modified into hard wing coverings called elytra. In some insects, either a portion of or the entire first pair of wings is leathery. Variation in the number of wings, size, position, veination, and shape are clues to identification. The Insect Abdomen This is the third body region which has numerous segments, the spiracles and external reproductive organs. Spiracles are the exterior opening of the respiratory system; some insects hove one pair on each abdominal segment. In most insects, the external reproductive organs used for copulation are on the lost two abdominal segments. Some insects, such as cockroaches, crickets, and silverfish have segmented appendages called cerci which extend from the tip of the abdomen. Class Arachnid. The characteristics of this class include: no wings and antennae, one or two body segments (Le., head/thorax and abdomen), and four pairs of walking legs. There are terrestrial and freshwater species. Major orders include: Acari (mites and ticks) —The head, thorax and abdomen appear to be combined, however, they have the two body regions typical of arachnids — cephalothorax and abdomen — and often are sac-like in form. The adults and nymphs have four pairs of legs; larvae, however, have only three pairs. They have piercing sucking mouthparts, and the central tube (hypostome) in ticks has recurved teeth; mites, however, lack teeth. Ticks and mites undergo simple metamorphosis (i.e., egg, larva, nymph and adult). Araneae (spiders) — Spiders have two body regions — a cephalothorax (head and thorax) and an abdomen — which are connected by a tiny waist (pedicel). The abdomen is bulbous and unsegmented and has several silk producing spinnerets at the tip. Spiders have four pairs of legs, and most species have six or eight simple eyes. A pair of jaws which end in a hollow fang is located below the eyes. Most spiders have venom although most are incapable of biting. Spiders undergo simple metamorphosis (i.e., eggs, spiderlings, and adults). Scorpiones (scorpions) — These arachnids have two body regions— cephloathorox and abdomen. The long segmented abdomen usually is curved upward ending in a stinger which contains a venom gland. A large pair of pincers are attached to the cephalothorax and are used to capture and hold prey. Class Crustacea (crabs, sowbugs, and copepods). The characteristics of this class are as follows: wingless, two pairs of antennae, two body regions (i.e., cephalothorax and abdomen), and ten or more pairs of legs. Most species are marine, but there are a few freshwater and terrestrial species. Isopoda (pillbugs and sowbugs)— These isopods are oval-shaped and appear to have body armor. They do not have a cover over the cephalothorax (i.e., head and thorax combined). They have two pairs of antennae, the second of which is very small, and seven pairs of legs. Class Chilopoda (centipedes). The characteristics of this class include: wingless, one pair of antennae, flat worm-like body with many segments, and a single pair of legs on most body segments. All species are terrestrial. Class Diplopoda (millipedes). The characteristics of this class include: wingless, one pair of antennae, cylindrical worm-like body with many segments, and two pair of legs on most body segments. All species are terrestrial. Class Hexapoda (insects). The characteristics of this class include: one pair of antennae, three body regions (i.e., head, thorax and abdomen), three pairs of legs, and one or two pairs of wings which sometimes are absent. Most species are either terrestrial or freshwater but a few are marine. Major orders of structural pests include: Anoplura (sucking lice) — These are small, flattened, and wingless blood-sucking parasites of worm blooded animals. The mouthparts, which ore adapted for piercing and sucking, are withdrawn into the head when the insect is at rest. The compound eyes are either small or absent. The tarsus is single-segmented with one large claw adapted for hanging onto hairs. Lice undergo simple metamorphosis (i.e., egg, nymph, and adult). Blattodea (cockroaches) — These insects are easily recognized by their oval-shaped and dorsally-ventrally flattened body. The head is concealed from view by the first dorsal thoracic shield (i.e., pronotum). They hove four wings; the first pair has veins and are parchment-like and completely cover the second pair which are cellophane-like. A few species in this class of insects lack fully developed wings and have short stubbly wing pads. The antennae are long and thread-like, and the mouthparts are chewing. The tip of the abdomen has two segmented projections (i.e., cerci), however they ore not pincer-like. Cockroaches undergo simple metamorphosis (i.e., egg, nymph, and adult). Coleoptera (beetles and weevils) — In most species, the front pair of wings is thick and shell-like, meet in a straight line down the middle, and serve as wing covers (i.e., elytra) for the second pair of cellophane-like wings folded underneath. Antennae usually have eleven or fewer segments and range in size from inconspicuous to more than twice the body’s length. The mouth-parts are chewing and, in the weevils, are at the end of a snout or projection from the front of the head. Beetles and weevils undergo complete metamorphosis (i.e., egg, larva, pupa, and adult). Collembola (springtails) —These very small insects are wingless, and their abdomens have six or less segments. Most species have a forked structure (i.e., furcula), the “spring” attached to the tip of the abdomen normally tucked under the body. In addition, there is a tubular structure (i.e., collophore) on the underside of the first abdominal segment. They have short antennae and chewing mouthparts. Springtails undergo simple metamorphosis (i.e., egg, nymph, and adult). Dermaptera (earwigs) —These are elongate and flattened insects with four pairs of wings, the first of which are short and hardened and the second of which are cellophane-like and folded under the first pair. The antennae are thread-like and about half as long as the body. They have chewing mouthparts and compound eyes. The tip of the abdomen has two segmented pincer-like projections (i.e., cerci). Earwigs undergo simple metamorphosis (i.e., egg, nymph, and adult). Diptera (flies and mosquitoes) — These insects have one pair of cellophane-like wings, the second pair of wings is modified into knob-like structures (i.e., halteres) used for balance. In contrast to other flies, mosquito wings are covered with small scales. The compound eyes are large, and the antennae are often small and inconspicuous. In mosquitoes and other blood feeding flies the mouthparts are piercing and sucking; in filth flies, the mouthparts are sponging. Flies undergo complete metamorphosis (i.e., egg, larva or maggot, pupa, and adult). Heteroptera (true bugs) — The first pair of wings is thickened at the base and appear leathery; the remainder of the wing is cellophane-like. The second pair of wings is cellophane-like and concealed by the first pair which are held flat over the body. A few bugs, e.g., bedbugs and bat bugs, are wingless. The mouthparts ore piercing and sucking and arise from the front part of the head; however, at rest, the mouthparts are held under the body. Bugs undergo simple metamorphosis (i.e., egg, nymph, and adult). Hymenoptera (bees, wasps and ants)— These insects hove two pairs of cellophane-like wings, the second pair is slightly smaller than the first. Worker ants are wingless; however, many species produce winged swarmers at least once annually. The constriction between the thorax and the abdomen is more noticeable in wasps and ants. In ants, this constriction is referred to as the petiole and consists of one or two segments (i.e., nodes). Most species have well-developed compound eyes, the antennae are usually 12 to 13 segments (and elbowed in ants), and the mouthparts are either chewing or chewing-lopping. Bees, wasps, and ants undergo complete metamorphosis (i.e., egg, larva, pupa, and adult). Isoptera (termites) — These wood-attacking insects are divided into several castes (i.e., divisions of labor) — workers, soldiers, kings, and queens. Once a colony is established, all the individuals are wingless; however, during the year, winged swarmers (i.e., kings and queens) are produced. The two pair of wings are cellophane-like, longer than the body, and equal in size. Although the workers are commonly referred to as white ants, they lock the narrow waist (i.e., petiole) characteristic of ants. Workers and soldiers do not have compound eyes, the mouthparts are chewing, and the antennae are long and bead-like. Termites undergo simple metamorphosis (i.e., egg, nymph, and adult). Lepidoptera (butterflies and moths) — Most of these insects have two pair of cellophane-like wings, the second of which is smaller than the first, which are covered with colorful scales that easily rub off when handled. The mouthparts are siphoning and coiled into a tube under the head. The antennae are usually long and slender although the butterfly antennae end in a knob. Butterflies and moths undergo complete metamorphosis (i.e., egg, larva or caterpillar pupa, and adult). The caterpillar has chewing mouthparts; most hove small legs (i.e., pro-legs) with small hooks (i.e., crochets) on the bottom. Orthoptera (crickets) — The adults are either wingless or have two pair of wings. The larger first pair of wings is long, narrow, and thickened, and the hind wing is membranous and kept under the front pair. They have chewing mouthparts, and the antennae usually are long and have numerous segments. The tip of the abdomen has two segmented projections (i.e., cerci) which are either short and pincer-like or long and feeler-like. Some female crickets have a long projection (i.e., ovipositor) extending from the tip of the abdomen which is used to lay eggs. Crickets undergo simple metamorphosis (i.e., egg, nymph, and adult). Psocoptera (psocids and booklice) —These are very small soft-bodied insects which may or may not have wings. If wings are present, there are two pair which are held roof-like over the abdomen when the psocid is resting. They have chewing mouthparts and long slender antennae. Psocids undergo simple metamorphosis (i.e., egg, nymph, and adult). Siphonoptera (fleas) —These bloodsucking parasites of mammals and birds are very small, wingless, and have laterally flattened bodies. Their legs are modified for jumping, and they have various patterns of spines on their bodies which assist them in hanging onto animal hairs. The mouth parts are piercing and sucking, the antennae are short and inconspicuous, and the compound eyes may or may not be present. Fleas undergo complete metamorphosis (i.e., egg, larva, pupa, and adult). Thysanura (silverfish and firebrats) — These tear drop-shaped, wingless insects have scales on their bodies, chewing mouthparts, and three long tail-like appendages at the tip of the abdomen. Silverfish and firebrats undergo simple metamorphosis (i.e., egg, nymph, and adult). The following key to the arthropods of public health importance is included for assistance in identifying structural pests. Key to Adult Arthropods Described in this Guide 1. With three or four pairs of legs; With five or more pairs of legs. 2. With four pairs of legs; no antennae — spiders, ticks, mites, and scorpions (Class Arachnid); With three pairs of legs and one pair of antennae — insects (Class Insecta) 3. Typically 5-7 pairs of legs; two pairs of antennae — crabs, shrimp, lobster, copepods (Class Crustocea); Body oval and flattened; seven pairs of legs, In damp places such as logs, mulch, crawl spaces — pillbugs and sowbugs (Order Isopoda); Body long and narrow; 10 or more pairs of legs; one pair of antennae. 4. Body segments flattened, with one pair of legs per body segment — centipedes (Class Chilopoda); Body segments cylindrical, most with two pairs of legs per body segment — millipedes (Class Diplopoda). 5. Abdomen joined to the cephalothorax (head and thorax combined) by a slender waist segmentation of abdomen indistinct or absent — spiders (Order Araneae); Abdomen broadly joined to cephalothorax; abdomen distinctly segmented and lengthened to form a long tail with a stinger at the tip — scorpions (Order Scorpionida); Abdomen broadly joined to cephalothorax; abdomen unsegmented and without a long tail with a stinger at the tip — ticks and mites (Order Acari) 6. Winged; Wingless 7. Front wings, at least partly hardened, leathery or parchment at base. Front wings membranous 8. With chewing mouthparts; With sucking mouthparts. 9. With pincers (cerci) at tip of abdomen — earwigs (Order Dermaptera); Without pincers at tip of abdomen 10. Front wings hard and shell-like, without veins, may have lines — bee (Order Coleoptera) Front membranous wings with branched veins 11. Jumping insects, hind femur enlarged; tarsi four or fewer segments — crickets (Order Orthoptera); Walking insects hind femur not enlarged; head concealed from above by pronotum (first dorsal thoracic segment); body flattened and elongate oval — cockroaches; (Order Blattodea) 12. Front wings leathery at base and membranous at tip — true bugs (Order Hemiptera); Front wings of uniform texture — cicadas, plant and leaf hoppers (Order Homoptera) 13. Two wings and two halteres (knob-like structures) — flies and mosquitoes (Order Diptera); Four wings. 14. Wings typically covered with scales; mouthparts long and coiled under head — moths and butterflies (Order Lepidoptera); Wings with few or no scales; mouthparts not long and coiled. 15. Hind wings equal to or larger than front wings held flat over abdomen; mouthparts close to eye; all legs walking type; cerci at tlp of abdomen short (two to eight segments) — termites (Order Isoptera); Hind wings smaller than front wings. 16. Tarsi (last segments of leg) composed of two to three segments; chewing mouthparts — booklice (Order Psocoptera); Tarsi composed of more than three segments (typically five); some with chewing mouthparts — ants, bees and wasps (Order Hymenoptera) 17. Antennae present collophore (tube-like stnicture on abdomen) present; like structure usually present — springtails (Order Collembola); Both collophore and spring-like structure absent 18. Two or three long tail-like appendages present — silverfish (Order Thysanura); Long tail-like appendages absent. 19. Body flattened laterally or dorso-ventrally (like a pancake); Body not flattened; abdomen and thorax narrowly joined together — ants (Order Ilymenoptero) 20. Body flattened laterally — fleas (Order Siphonuptera); Body flattened dorso-ventrally (like a pancake). 21. Sucking mouthparts externally visible; antennae longer than head — bed bugs and other hue bugs (Order Hemiptera); No sucking mouthparts externally visible. Antennae longer than head; first segment of tarus not swollen; tarsus composed of two to three segments; tiny insects — booklice (Order Psoccoptera) Antennae shorter than head; head narrower than the thorax at the point of attachment to the thorax — sucking lice (Order Anoplura) Prev: Inspection and Monitoring |