Insect Anatomy and Development PDF

ENT-68 Insects By Jonathan L. Larson, Extension entomologist. In this chapter: Species:...

ENT-68 Insects By Jonathan L. Larson, Extension entomologist. In this chapter: Species: melifera Identifying Insects 01 Insect Anatomy and Development 08 Genus: Apis Identifying Insect Pests by Damage 14 Family: Apidae Abbreviated Guide to Pest Management on Plants 15 Order: Hymenoptera Class: Insecta Phylum: Arthropoda I nsects are the most biodiverse group of animals on earth. Amazingly, there are about one million total species of insects known currently, with the possibility of tens of millions more Kingdom: Animalia Domain: Eukaryota left to discover. When you include spiders, mites, scorpions, Figure 7.1. A pyramid showing the increasing specificity of terms millipedes, centipedes, and other relatives, it’s astounding to see referring to a European honey bee. the diversity of this group and how dominant they are across the planet. Not only are there many different species, but you and genus. When talking about insects and their relatives, we can encounter these organisms almost anywhere on earth, from will be referring to them by their phylum name, Arthropoda, the bottom of the ocean to your own living room. or more simply, the arthropods. This group represents almost Insects and their relatives have a complicated relationship 80 percent of animal life on the planet. with humans. While most have no impact on human lives one way or the other, some can have negative impacts on us, while others are viewed as beneficial organisms. Insects that Arthropods cause problems are collectively known as pests; only about Representatives of the arthropods can look radically different one to three percent of the total population of insects would be from one another—think of comparing a monarch butterfly to considered true pests. Beneficial insects may provide goods or a lobster. However, despite their differences, there are some services that humans value. Honey bees for example, provide traits that all arthropods share. pollination services, helping farmers to produce things like All arthropods have jointed appendages. The name “arthro- apples, as well as goods like honey and beeswax. The vast major- pod” translates as “jointed foot.” ity of insects though are simply wild animals trying to survive. Arthropods all display bilateral symmetry. If a line is drawn As Master Gardeners, you will receive many inquiries about down the middle of their bodies, the two sides should be a insects, particularly those that are plant pests. This could involve mirror image of each other. insect identification and making pest control recommenda- All arthropods have segmented bodies. Importantly, the dif- tions. In order to successfully identify pests and provide help, it ferent classes of arthropod are often separated by the number will be helpful to understand some of the basic natural history, of segments their bodies have. anatomy, and biology of insects and their relatives. Across the phylum, all representatives have an exoskeleton, a waxy outside layer that protects them, rather than having an internal skeleton like humans do. Identifying Insects Scientists have created a classification system for organisms Classes that divides them into various groupings. These groupings are There are multiple classes of arthropods that can be sepa- part of a tiered system, which can be best visualized as a pyra- rated by certain physical traits, such as the number of body mid. The base of the pyramid is the most generalized way of segments, number of legs or antennae, and the presence of talking about a specific organism, currently this level is called other specialized anatomy. “domain”. The top of the pyramid is the most specific way of talk- ing about a specific organism; currently this level is called “spe- cies” (Figure 7.1). In between these levels there are also (in order of increasing specificity) kingdom, phylum, class, order, family, CHAPTER 07 Insects Crustacea (Crabs, Lobsters, Shrimp, Crayfish, Isopods) Arachnida (Spiders, Ticks, Mites, Scorpions) Members of this class have two pairs of antennae, two body A very diverse class, containing predators, herbivores, segments, and five to seven pairs of walking legs (Figure 7.2). As parasites, and decomposers. All representatives have two body a group, they tend to be found in bodies of water. Pillbugs and segments, four pairs of legs, and specialized mouthparts known sowbugs (a.k.a. rolly pollies) are terrestrial, though they live in as chelicera (Figure 7.5). damp environments. 5430920 Figure 7.2. Crustacea. Chilopoda (Centipedes) Centipedes have one pair of antennae and one pair of legs per body segment (Figure 7.3). They tend to have a flattened profile and are predaceous. To subdue prey, they have a pair of UGA5005062 venomous fangs. Contrary to what their name implies, they don’t typically have one hundred legs. Figure 7.5. Arachnida. Insecta (Beetles, Butterflies, Dragonflies) While members of this class vary wildly in shape, size, color, and environmental role, they all share some traits. Insects have three body sections, three pairs of legs, and one pair of anten- nae (Figure 7.6). 5380086 Figure 7.3. Chilopoda. Diplopoda (Millipedes) Millipedes have one pair of antennae and two pairs of legs per body segment (Figure 7.4). They tend to have a tubular profile and are decomposers. Like their cousins, the centipedes, their name is a bit of a misnomer. It translates to “thousand feet” but most species have nowhere near that many legs. 5533027 5490052 Figure 7.4. Diplopoda. Figure 7.6. Insecta. 7-2  Insects CHAPTER 07 Orders characteristics, but with the advent of genetic analysis, great shifts have occurred in our understanding of what is truly After classes, organisms will be classified in an order. For the related to one another in the world of insects. Generally speak- sake of this chapter, we’ll focus on orders of insects to help you ing, all members of an order will share certain physical char- identify them in the future. Order level identification is often acteristics and will develop in similar ways (Figures 7.7–7.18). the level needed to help with pest problems. Not all orders Anatomically, the most important traits that separate insect are prevalent in Kentucky; some others can be found nearly orders are the types of mouthparts, types of legs, and number anytime and anywhere. of wings. Different orders will also progress through different There are about 30 orders of insects. This number fluctuates types of metamorphosis as they mature. For more information with new discoveries; entomologists may create new orders on these anatomical and biological differences, see the second or fold one order into another, based on new genetic informa- half of this chapter. tion. Previously, orders were compiled based solely on physical 5482930 UGA5304027 Figure 7.7. Odonata. Figure 7.8. Orthoptera. Odonata Orthoptera Dragonflies and Damselflies Grasshoppers, Crickets, and Katydids Odonata means “toothed,” referring to the toothed parts of Orthoptera means “straight wing,” and these insects bear their mouths. folded wings that form a straight line down the back. Big Eyes and Skinny Jumping and Singing Odonates tend to have long, thin abdomens; heads that are Most orthopterans have a hind pair of jumping legs and use mostly covered with compound eyes; and vein-filled wings. songs to communicate. Incomplete Metamorphosis Incomplete Metamorphosis Odonates hatch from their eggs and develop through Orthopterans hatch from their eggs and develop through nymphal stages, gradually developing underwater. nymphal stages, gradually growing and developing wings. 7-3 CHAPTER 07 Insects 5380102 Figure 7.10. Blattodea. Blattodea Cockroaches and Termites Blattodea means “cockroach.” Termites were added to this order after recent genetic research. Basic Legs and Antennae Cockroaches and termites have simple walking legs. Cockroaches tend to be flattened, with a protected head. Termites are pale in color and live in colonies. Incomplete Metamorphosis Roaches and termites hatch from their eggs and develop through nymphal stages. UGA5192029 Figure 7.9. Mantodea. Mantodea Praying Mantises Mantodea means “prophet.” There are three mantis species in Kentucky. Predatory Attributes 5380222 Mantises have raptorial front legs and triangular heads with large eyes, both aiding in catching prey (usually other insects). Figure 7.11. Dermaptera. Incomplete Metamorphosis Dermaptera Mantises hatch from their eggs and develop through nymphal stages, gradually growing and developing wings. Earwigs Dermaptera means “skin wing,” referring to the skin-like front-wing covers of earwigs. Cerci and Ear-Shaped Wings Earwigs are most recognized by the pincerlike cerci on their rear. When unfolded, their wings are ear shaped. Incomplete Metamorphosis Earwig mothers tend to their eggs over the winter. When they hatch, earwig nymphs will emerge. 7-4  Insects CHAPTER 07 5554357 5386081 Figure 7.12. Thysanoptera. Figure 7.13. Hemiptera. Thysanoptera Hemiptera Thrips Aphids, Cicadas, Stink Bugs, Assassin Bugs, and More Thysanoptera means “fringe wing,” referring to the hairy- Hemiptera means “half wing.” Some hemipterans have half- looking fringe on thrips’ wings. leathery and half-membranous wings. Slender with Hairy Wings Piercing–Sucking Mouthparts Thrips are small and pencil shaped, with fringed wings and All hemipterans have needle-like mouthparts that can be asymmetrical mouthparts. used to siphon their food. Strange Metamorphosis Incomplete Metamorphosis Thrips are sometimes considered to have development that Hemipterans hatch from their eggs and develop through is both complete and incomplete metamorphosis. nymphal stages, gradually growing and developing wings. 7-5 CHAPTER 07 Insects 5490407 Figure 7.14. Neuroptera. Neuroptera Lacewings and Antlions Neuroptera means “nerve wing,” referring to the many veins in the wings of this group. Slender with Vein-Filled Wings Adults look vaguely like dragonflies but with long antennae, and their wings have many veins in them. Complete Metamorphosis Neuropterans are larvae when immature, looking consider- ably different from their adult form. 5550224 Figure 7.16. Lepidoptera. Lepidoptera Butterflies, Moths, and Skippers Lepidoptera means “scale wing,” referring to the scalelike coating on the wings. Siphons and Scales Lepidopterans have colored scales covering the wings and UGA1233224 siphoning mouthparts that curl under their heads. Figure 7.15. Coleoptera. Complete Metamorphosis Lepidopterans hatch from their eggs as larvae, usually Coleoptera referred to as caterpillars, which will pupate before becoming adults. Beetles Coleoptera means “sheath wing,” referring to the hardened top wing that protects the soft underwing. Tough Wing Covers Beetles have tough wing covers called elytra, along with chewing mouthparts and two pairs of wings. Complete Metamorphosis Beetles hatch from their eggs as larvae, sometimes referred to as grubs. They will pupate before reaching adulthood. 7-6  Insects CHAPTER 07 5549600 5387759 Figure 7.17. Diptera. Figure 7.18. Hymenoptera. Diptera Hymenoptera Flies Bees, Ants, Wasps, and Sawflies Diptera means “two wings,” as flies only have two full wings. Hymenoptera means “membrane wing,” referring to the insects’ four see-through wings. Two Wings and Aristate Antennae All flies have two wings, and most also have aristate antennae Membrane Wings and Social Structures and sponging mouthparts. Hymenoptera have chewing mouthparts and two pairs of membranous wings. Many live in social colonies. Complete Metamorphosis Flies hatch from their eggs as larvae, usually called maggots, Complete Metamorphosis and they will pupate before they mature into adulthood. Hymenopterans hatch from their eggs as larvae and will pupate before reaching adulthood. Inside of each order can be numerous families of insects. Common names are important, as they are what most Family-level identification is also helpful when identifying a people will use when discussing insects and they are easier to specimen, as the extra specificity may provide a more targeted understand than Latin genus and species names. Common management approach or reveal that something isn’t a pest at all. names can also be confusing though, as they vary by location Animal family names end in “-idae”—for example, Coccinellidae and are sometimes applied to multiple insects. For example, the (lady beetles), Tettigoniidae (katydids), and Culicidae (mos- common name “potato bug” could refer to either a Colorado quitoes). Most families also have distinct traits that help with potato beetle or to a Jerusalem cricket, depending on whom quicker identification. To use Coccinellidae as an example, they you ask. Similarly, the insects that fly in the summer and glow are generally recognized by their bright warning coloration, could be called lightningbugs or fireflies, depending on where spots, and domed appearance. you are in the state of Kentucky. These confusing situations are Beyond the family will be genus and species. Identification why you might hear an entomologist using the more specific of insects to these levels usually requires the use of a dichoto- scientific names instead of common names. mous identification key and magnification equipment. Some Other common name issues can arise from the terms “fly” species may be separated by something difficult to see, such as and “bug.” Flies and bugs are both specific kinds of insects. Fly the number of hairs found on a specific part of the antennae. is the term broadly applied to the order Diptera, while bug or Other times, it’s possible to recognize the species quickly and true bug is applied to the order Hemiptera. However, common easily. For example, a Japanese beetle has a distinct enough names may borrow these terms and apply them to insects out- appearance that it can be identified almost immediately. side of those two orders. The way to tell if “fly” or “bug” is being Genus and species names are combined to make an insect’s used to describe an actual fly or bug is to look for a space before binomial scientific name. To stick with Japanese beetle, its sci- the word “fly” or “bug”. The word “firefly” is a good example of entific name is Popillia japonica. Japanese beetle is this species’ this. Fireflies are actually a type of beetle; therefore, there is no common name. space before the word “fly.” A house fly, on the other hand, is a true fly, and there is a space before the term “fly” when writ- ing the name out. With the term “bug,” you can see this with a ladybug (a beetle) versus a bed bug (a true bug). 7-7 CHAPTER 07 Insects Insect Anatomy and Development As described before, insect anatomy is key to understanding how to identify insect specimens. Looking at the basic body plan of an insect, there are three body sections: the head, thorax, and abdomen. Each section will have specialized internal and external anatomical structures that help the insect be successful and help us to tell what it is. Head The head is where the insect receives most of the sensory information it needs to find other members of its species group, 5571554 food, and shelter. This information is acquired through sensory Figure 7.19. Insect ocelli, such as the ones inside of the yellow tri- organs housed on the head, namely the eyes, antennae, and angle here, are often in groups of three on top of an insect’s head. mouth. Inside of the head is the first and largest of an insect’s multiple ganglia, or brains. Insect Eyes Insects can have two kinds of eyes: simple eyes (also referred to as ocelli) and a pair of compound eyes. Ocelli are able to detect only light and darkness. Insects may use them to know what time of day it is. Ocelli often come in groups of three, arrayed in a triangle on top of the insect’s head (Figure 7.19). Insects have a pair of compound eyes that gather more visual information (Figure 7.20). Each compound eye is made up of hundreds or thousands of lenses, each of which will send an image to the insect’s brain. This multitude of images is compiled into a collage-like visual. Insect vision lacks depth perception, and they tend to be near-sighted. Insect compound eyes are capable of detecting ultraviolet light, though. Insect Antennae 5459067 All insects have a pair of antennae, usually located on top of Figure 7.20. Compound eyes, like the two red ones on this house fly, the head or at the front of the head. Antennae are used variously can collect visual information from around the insect; most insects for smelling, touching, and even hearing. To facilitate smelling, are considered to have poor vision, though. 5490053 5385891 Figure 7.21. The two most common types of insect mouths are chewing (image of the beetle on the left) and piercing-sucking (wheel bug on the right). 7-8  Insects CHAPTER 07 the antennae are covered with small hairlike receptors that col- the insect to pierce a food source and then slurp the juices out lect odorous cues. This allows the insect to detect food from afar, of it. Piercing-sucking mouths can be used on plants by her- to confirm that something is food, and to detect pheromones bivores to draw out sap, on animals by parasites to draw out produced by other members of its species. Antennae can be blood, or on other insects to consume their innards by preda- quite helpful for identifying insects to order and family, as there tors. Hemipterans have piercing-sucking mouthparts, as do a are lots of different shapes and forms of antennae (Table 7.1). few others like mosquitoes. Insect Mouthparts Chewing and Lapping Anatomically, insect mouths are made up of multiple struc- Chewing and lapping mouths are found on insects that chew tures. There are mandibles, different kinds of palps, and pieces pollen and drink nectar, such as honey bees. This type of mouth that function like lip covers, in a way. Taken as a whole, these will have chewing mandibles but also a long tube or tongue to pieces may be called the insect’s mouthparts. Insects feed on consume liquids as well. a great diversity of food, and mouthparts can be specialized to Sponging help the insect consume whatever food it feeds on (Figure 7.21). Found on many Dipterans (flies), sponging mouthparts have Chewing a structure that helps them to absorb liquids from surfaces. The most common of insect mouths, chewing mouth- Some sponging mouths may be paired with sharp cutting parts feature two mandibles, opposing one another, that organs to help gain access to blood. chew up food. Depending on the species, this could be for Siphoning herbivory or for predation. Mandibles are usually toothed to Moths and butterflies have siphoning mouths, simple, tube- facilitate chomping. like mouths that curl up under the head when not in use. They Piercing and Sucking can be unfurled and dipped into things like flowers to drink up The second most common type of insect mouths, piercing liquid food, such as nectar. and sucking mouthparts have been heavily modified to allow Table 7.1. Insect antenna types, and insects that most commonly have them. Antennae Type Bearing Insects Filiform Found in almost every order, and prevalent in The most basic of insect antennae, simple and Orthoptera, Mantodea, Blattodea, Dermaptera, threadlike and Neuroptera 5604059 Serrate Antennal segments have small triangular projec- Found mainly on beetles tions that appear like saw teeth to humans 5611543 Lamellate Start out thin but have finger- or page-like pro- Found mainly in scarab beetles jections at the tip UGA2146008 7-9 CHAPTER 07 Insects Continued from previous page. Table 7.1. Insect antenna types, and insects that most commonly have them. Antennae Type Bearing Insects Pectinate Found mainly on beetles, sawflies, and parasitoid Long, fingerlike projections on one side of anten- wasps nal segments, like a comb 5596601 Plumose Most common on moths and mosquitoes, but Feather-like, usually with projections on two may only be on males in certain species sides of the antennae 5444467 Aristate Small, feather-like antennae that sit on top of a Found typically on flies bulbous structure 5463550 Setaceous Found on fast flying insects, dragonflies, water Very simple and thin, looks like an individual hair bugs, cicadas, etc. 5444475 Geniculate Most associated with ants and other Elbowed antennae, look similar to filiform with Hymenopterans a joint in the middle 5393435 Capitate Found on butterflies as well as some Neuropterans Antennae terminate in a bulbous tip, knobbed and beetles in appearance 5367893 Clavate Clubbed antennae that gradually get thicker Found on beetles and moths most often toward the tip 5380080 7-10  Insects CHAPTER 07 Thorax allowing the insect to jump many times its own body length (Figure 7.22b). The next body section is known as the thorax. The thorax itself is split into three sections: the pro-, meso-, and metatho- Natatorial raxes. One pair of legs is attached to each section. Aquatic insects can have natatorial legs. These are usu- The thorax starts where the first pair of legs are and ends ally flattened and oar shaped, and sometimes they will have with the last pair of legs. This section specializes in locomotion; a dense coating of hairs that also help to push water as they not only are the legs attached here to facilitate movement but if swim (Figure 7.22c). the insect is winged, this is where the wings will attach as well. Fossorial Insect Legs These legs are designed for digging into soil. Part of the leg Depending on the order they belong to, insects may have will be modified to scrape soil. Scarab beetles, mole crickets, different kinds of legs. Legs may also help facilitate identifica- and several other families of insects will have a pair of them tion. Insect legs are structurally similar to human legs, with a (Figure 7.22d). coxa ball joint, a first section called the femur, a tibia, and tarsi Clasping at the end. These legs have been modified to allow an insect to grasp Walking onto hairs or feathers. They are most associated with lice Most insects will have at least one or two pairs of walking (Figure 7.22e). legs. These are very simple legs with no special adaptations. Raptorial They help the insect to scurry along (Figure 7.22a). These predatory legs have been modified so that the tibia Jumping and femur can close on one another, similarly to a bear trap. Grasshoppers, katydids, crickets, and fleas are most famous Mantises, giant water bugs, and mantis wasps are the insects for having jumping legs. This type of leg looks like a walking leg, most commonly associated with these legs (Figure 7.22f ). except the femur will be larger and packed with more muscles, 22a 22b 5581870 5573937 22c 22d 5403786 UGA5190033 22e 22f 5511979 5604058 Figure 7.22. Insect legs are suited to the lifestyle of the bug they are attached to. 7-11 CHAPTER 07 Insects Insect Wings are tactile organs that serve as sort of rear antennae. Some cerci Insects are the only invertebrates that have wings. Usually, are short (like on cockroaches), while others may be quite long they are clear and membranous, with noticeable veins inside (mayflies). Earwig cerci are hardened and antler-like, helping of them. Some wings have been modified and can be helpful to separate their order from others. with identification. Lepidopteran wings are coated with scales and are opaque. The front wings of beetles, known as elytra, Insect Development are hardened and leathery. They help to protect the softer, Insects use internal fertilization to reproduce. After mating, membranous hind wings. female insects can fertilize their eggs and then will usually lay Not all insects are winged. Some, like silverfish and firebrats, them outside of the body. Depending on the type of insect, have never had wings. Others, like fleas and bed bugs, once after an egg hatches, the insect will either be a nymph or a larva. had wings but over time they became greatly reduced, as these Nymphs go through incomplete metamorphosis, and larvae go insects found other modes of movement and did not need the through complete metamorphosis. wings anymore. Only adult insects have wings. Incomplete Metamorphosis Abdomen Also known as hemimetabolous development or gradual The final body section is the abdomen. It can be made up of metamorphosis, incomplete metamorphosis involves a eight or more segments. Internally, the abdomen houses many nymphal stage that looks similar to the adult form, except important organs; much of the digestive tract, circulatory sys- smaller and lacking wings (Figure 7.23). Gradually, the insect tem, respiratory system, and nervous system are housed here. will develop through several nymphal stages, shedding Most importantly, the insect reproductive system is in the abdo- their exoskeleton in between each. Hemiptera, Orthoptera, men. Externally, on female insects, an ovipositor may be noticed Mantodea, Blattodae, Dermaptera, and Odonata (amongst on some groups. These are often sword-like or stinger-like. Cerci others) develop through incomplete metamorphosis. may also be seen at the tip of some insects’ abdomens. Cerci egg nymph nymph adult Figure 7.23. Stages of gradual metamorphosis. egg larva pupa adult Figure 7.24. Stages of complete metamorphosis. 7-12  Insects CHAPTER 07 a. b. Figure 7.25. Basic larval types. a. Predator (some beetles, lacewings). Characteristics include a streamlined body with hard exoskeleton, long thin legs, and big, often a. b. sharp, jaws at the front of the head. b. White grub. This type has a distinct yellow-brown a. b. head with large jaws and a soft, white, curved body with distinct legs. This type is usually a root c. feeder, but some larvae of this type live in decay- ing organic matter. Japanese beetles and green a. b. June beetles have this larval type. a. b. c. Caterpillar. This type has a distinct head; a long, cylindrical body with three pairs of segmented legs; and two to five pairs of fleshy legs along the c. d. abdomen. This is the larval stage of butterflies and c. moths. Many caterpillars are striped or brightly col- ored, but caterpillar larvae that bore in plants are usually white or cream-colored. Sawflies are similar but have fleshy legs on all abdominal segments. d. d. Wireworm. This larval type has a round, cylindrical c. c. body that is hard and yellow or brown. It has three d. pairs of short, segmented legs behind the head e. but no fleshy legs on the abdomen. These larvae may live in the soil and feed on seeds or plant roots; some live in decaying logs. Some beetles have this form. d. d. e. Leaf beetles. This type is similar to caterpillars e. but has no fleshy legs on the abdomen. Many leaf beetles feed on leaves and are camouflaged e. f. by color and markings. Some have white, thinner bodies and live in the soil, where they feed on plant roots. f. Maggots. This type is headless, legless, soft- bodied, and white or cream-colored. They are the e. e. f. larvae of flies. g. f. g. Legless grubs with distinct heads. Many feed in plants or seeds. Bees and wasps have this type of larva. Figure 7.25. Stages of complete metamorphosis. g. f. f. Complete Metamorphosis begin or continue developing. For the insect to move from one g. stage of life to the next, that temperature needs to be reached or Also known as holometabolous development, this is the most common type of metamorphosis that insects go through maintained for a certain number of days. We call these “growing (Figure 7.24). In this type, the egg will hatch and a larvae will degree days,” and we can use temperature data to calculate them emerge. Larval insects usually g. look radically different from and predict insect emergence times. Simply put, the cooler the g. temperatures, the slower they develop, and the warmer it is, the their adult form (Figure 7.25). Larvae may have special names, such as caterpillars (immature Lepidoptera), grubs (immature faster they develop. Coleoptera), or maggots (immature Diptera). Larvae lack Winter presents an issue for insects; the cold could mean wings and usually feed on different food than the adult form death, since they can’t warm themselves. To deal with this, dif- will; for example, caterpillars eat leaves usually, while adult ferent types of overwintering strategies have been developed. moths consume nectar. Between the larval and adult stages, Some insects will literally leave the cold area and migrate to a the insect will pupate. Pupae are an intermediate stage between warmer location to spend the winter months. The monarch immature and mature forms. Coleoptera, Diptera, Lepidoptera, butterfly is a famous example. Some insects, like stink bugs or Hymenoptera, Neuroptera, and many other orders use this type lady beetles, will stay in the cold location but huddle together in of development. a protected area to avoid cool air temperatures. Other species have timed their development so that they spend the winter Growing Degree Days and Overwintering as an egg or as a pupa, usually in a protected area. These stages Insects generally can’t control their own temperature, and don’t require food and don’t move, ideal traits in the dead of their development speed is determined by the temperature winter. Finally, some insects can produce antifreeze compounds around them. Each species has different requirements, but in their body to prevent full freezing. there is usually a temperature they need to reach in order to 7-13 CHAPTER 07 Insects Identifying Insect Pests by Damage Health Pests: These pests may be human health hazards or veterinary issues. Fleas, mosquitoes, and bed bugs are com- While most insects may not be pests, the ones that are can mon examples that can serve as vectors for disease or cause cause considerable damage and can be expensive to manage. emotional distress. There are multiple categories of pests, clustered based on what For Master Gardeners, the plant pests are usually the insect they are causing damage to. pests you will deal with most often. These pests attack differ- Plant Pests: Plant pests may attack crop plants being grown ent parts of the plant, including leaves, flowers, fruit, stems, for food or ornamental plants grown for beauty. and roots. As plant pests feed, they often leave behind diag- Urban Pests: Insects and other arthropods that enter struc- nostic symptoms that can help to deduce what pest you are tures and cause issues can be addressed as urban pests. Some dealing with. may be structural pests, such as termites, that actually harm the structure itself. Others may be annoyances, such as home- Chewing Pests invading ants. Finally, some may be stored-product pests, If pests chew on leaves, they can create damage such as organisms that will attack foodstuffs in storage and consume skeletonization, where the leafy tissue is consumed and veins them. Indian meal moth is a good example. are left behind (Figure 7.26); shot hole damage, showing small, irregularly shaped holes in leaves; and complete defoliation, where the leaves are gone or only the midrib is left. Each of these is associated with specific types of pests; scarab beetles tend to skeletonize leaves, shot hole damage is usually caused by flea beetles, and complete defoliation is usually from cater- pillars or sawflies. Sucking Pests Pests with piercing and sucking mouthparts will pull fluids from the host plant. This can result in droopy, wilted-looking leaves; cupped leaves; leaf yellowing; and early leaf drop (Figure 7.27). Sucking pests also generally produce honeydew, a sticky fecal material found near the population of pests. Mining and Boring Pests The mature stages of these plant pests feed inside of part 5443540 of the host plant. Leafminers create diagnostic mines in the leaves of host plants. These tunnels can be noticed from the Figure 7.26. Chewing damage can look like this skeletonized leaf, outside. There are three types: serpentine mines, blotch mines, where scarabs have consumed the green tissue and left the veins behind. and linear blotch mines. The shape, paired with the host plant name, will usually reveal what species is the problem. Wood- boring pests can create distinctive piles of frass on the outside of infested trees or leave behind diagnostic exit holes when they emerge as adults. Gall Makers These insects use secretions to induce the larval host plant to form a “home” around the immature insects. These galls come in different shapes and sizes; some look like small fingers, and others like apples. They can appear on leaves or stems. Usually, they present no hazard to the plant. Aside from these direct feeding or damage issues, some insects serve as plant pathogen vectors as well. This is similar to human health pests: the insect picks up a pathogen from one host plant and then moves it to another host plant, proliferating the disease. Sucking pests, such as aphids, thrips, planthoppers, leafhoppers, and mites, are most commonly associated with UGA1235159 disease vectoring, though some specific bark beetles may also serve as vectors. Figure 7.27. Sucking damage causes leaves to cup and curl, with pests often hiding in the cupped area. 7-14  Insects CHAPTER 07 Insect plant-disease vectors may have pathogens on their Monitoring for pests by observing plants in the landscape, bodies or inside their mouthparts, prompting transmission. regular sampling, or setting out traps can alert us to when Some may indirectly spread disease by damaging the plant and pest populations are rising and becoming a problem before creating a wound that a pathogen will enter to infect the host severe damage has occurred. Monitoring also allows for pest plant. Others may purposefully move fungal pathogens from identification, which can help to provide more specific pest tree to tree in order to grow them and consume them. management solutions. Natural enemy populations help to suppress but not elimi- nate pests. Adjusting expectations for the landscape from Abbreviated Guide to Pest perfection to a more natural equilibrium allows for beneficial Management on Plants predators and parasitoids to exist and function in a healthier ecosystem. Management of plant pests should be done through an Insecticides can be deployed for pest outbreaks or for issues integrated pest management (IPM) approach (See Chapter with invasive species that don’t have a natural solution. 10, Integrated Pest Management, for more information). This Organic and biorational products can be sprayed, hopefully means thinking about ways to utilize all of the tools for pest with less impact on non-target organisms such as pollinat- suppression that are available, rather than relying on any one ing insects. kind of management method. Pest problems can be prevented somewhat by making sure By following an integrated approach, growers can reduce that the right plant is put in the right place. Choosing spe- reliance on insecticides and keep themselves and the environ- cies or varieties not adapted for Kentucky can lead to higher ment healthy. stress for the plant, reducing defense and making the plant Other Resources to Consider: more attractive to arthropod pests. Further, when planting, consider selecting varieties that are pest resistant. Books Avoiding monocultures when planting creates more diversity Garden Insects of North America by Whitney Cranshaw for the landscape and can also help minimize pest popula- Tracks and Signs of Insects and Other Invertebrates by Charney tions. Diverse plants can also mean more natural enemies, and Eisman such as predaceous insects, in the landscape. Using good cultural practices such as sanitation of gardens in Web Resources the fall can help by removing overwintering habitat for pests Kentucky Pest News like squash bugs. Sanitation can also include the removal https://kentuckypestnews.wordpress.com/ and destruction of diseased or heavily infested plants. Other University of Kentucky Department of Entomology Factsheets cultural practices include proper watering, fertilization, https://entomology.ca.uky.edu/entfacts and pruning. 7-15 CHAPTER 07 Insects Photo Credits Braman Termite & Pest Elimination Natasha Wright, Bugwood.org—Figure 7.22d Bugwood.org Joseph Berger—Table 7.1: Geniculate, Figures 7.4, 7.13, 7.21b, 7.22b, 7.22c David Cappert—Table 7.1­: Lamellate, Figures 7.6, 7.12, 7.21a Mohammed El Damir—Figure 7.17 Johnny N. Dell—Figure 7.18 Kansas Department of Agriculture—Figure 7.22e Steven Katovich—Figures 7.16, 7.27 Mary C Legg—Figure 7.22a Wendy Patrick—Figure 7.5 Pest and Diseases Image Library— Table 7.1: Aristate, Figure 7.20 California Polytechnic State University at San Luis Obispo Gerald Holmes, Bugwood.org—Table 7.1: Filliform, Figure 7.22f Colorado State University Whitney Cranshaw, Bugwood.org—Figures 7.8, 7.14 University of Georgia Russ Ottens, Bugwood.org— Table 7.1: Capitate Rebekah D. Wallace, Bugwood.org—Table 7.1: Setaceous, Plumose Harvard University Gary Alpert, Bugwood.org— Table 7.1: Clavate, Figures 7.3, 7.10, 7.11 South Carolina Department of Natural Resources Allen Bridgman, Bugwood.org—Figure 7.9 USDA APHIS PPQ Quin Bayne, Sawfly GenUS, Bugwood.org—Table 7.1: Pectinate Tevan Brady, Exotic Bee ID, Bugwood.org—Figure 7.19 USDA Cooperative Extension Slide Series Clemson University, Bugwood.org—Figures 7.15, 7.26 USDA Forest Service Southern Research Station, Bugwood.org—Figure 7.7 US Geological Survey USGS, Bugwood.org—Figure 7.2 William Fisher Photography William Fisher, Bugwood.org—Table 7.1: Serrate Revised 01-2024