TRUE BUGS, CICADAS, AND RELATIVES: Hemiptera

PHYSICAL CHARACTERISTICS

The hemiptera are divided into four smaller groups based on their physical features. These groups include aphids, mealybugs, and scale insects; cicadas and hoppers; moss bugs; and true bugs. The relationships of whiteflies are uncertain, and they are sometimes included with aphids or hoppers.

Hemipterans are extremely variable in form, ranging from long, slender, and sticklike, to short and round, to very flat. The bodies of female scale insects are completely covered by a waxy shield. They don't even look like insects. Still other species are partially or completely covered in protective secretions of white wax that resemble dust, cotton, or feathers. The wax hides their bodies from predators and helps to seal in moisture. Hemipterans range in size from 0.03 to 4.3 inches (0.8 to 110 millimeters) in length. Their bodies come in a wide variety of bright or dull colors and patterns, and some species are virtually clear or colorless.

They have strawlike mouthparts for piercing plant or animal tissues and sucking out plant sap or body fluids. The mouthparts of most true bugs are long and flexible and are usually brought forward while feeding. The short, bristlelike mouthparts of all other hemipterans are permanently pointed backward toward the front pair of legs. In fact, the mouthparts of aphids, whiteflies, scales, and their relatives are actually attached between the front pair of legs. The antennae (an-TEH-nee), or sense organs, of all true bugs living on land are long and easy to see, but those of aquatic species and other hemipterans are usually short and bristlelike. Compound eyes, or eyes with multiple lenses, are usually present in most hemipterans; some species also have simple eyes, or eyes with only one lens.

Most adult hemipterans have four wings, but some species are wingless. The forewings of true bugs are thick and leathery at the base, but thin and membranelike toward the tip. The wings of true bugs are also folded flat over the back to form an 'X' pattern. The forewings of other hemipterans are entirely clear and membranelike or colored and slightly thickened. In many of these species, such as aphids and cicadas, all four wings have the same texture. Their wings are usually folded like a roof over the body with a single line running down the back. The legs of most hemipterans are especially fitted, or adapted for walking, running, jumping, swimming, or skating on water, grasping prey, or digging. In some species, such as scale insects and whitefly larvae (LAR-vee), the legs are greatly reduced in size or entirely absent.

The larvae of true bugs, or young of animals that must change form before becoming adults, are usually similar in appearance to the adults but are smaller and lack fully developed wings. However, the larvae of some hemipterans are very different from the adults. For example, adult whiteflies are slender with long legs, but their larvae are broad, flat, and lack legs.

GEOGRAPHIC RANGE

The hemiptera are found on all continents except Antarctica. They are even found on remote islands in the middle of the ocean. And they are the only insects that live on the surface of the ocean. There are about 82,000 species of hemiptera worldwide, with about 12,000 species in the United States and Canada.

HABITAT

Hemipterans live in nearly all kinds of aquatic and terrestrial habitats, from the seashore to high mountain peaks. Aquatic species live in fresh and brackish waters. They swim through the open water, crawl over the bottom or on plants, or skate across the surface. Sea skaters are the only truly marine insects and live their entire lives among mats of floating algae (AL-jee) on the surface of the ocean. Most hemipterans are terrestrial and are found on all parts of living plants. Some species live under the bark of dead trees. Others are found along the shores of ponds, lakes, streams, and rivers. Some species occur only in caves, spider webs, or animal nests, including those of other insects.

DIET

Most true bugs and other hemipterans suck fluids from leaves, stems, bark, flowers, seeds, and fruit, as well as algae and funguses. Other true bugs prey on living insects, spiders, slugs, snails, fish, frogs, and tadpoles. Some species prefer to feed on recently dead or dying insects. Some hemipterans, such as male scale insects, do not feed at all as adults. A few species such as bed bugs are parasites (PAE-rih-saits) on birds and mammals. Parasites live on another organism, or host, from which they obtain their food. The host is harmed but usually not killed by the parasite.

BEHAVIOR AND REPRODUCTION

Most hemipterans are active during the day. They spend most of their time feeding on plants, hunting for prey, and searching for mates and sites to lay their eggs. Some species, either as larvae or adults, gather in large, temporary feeding groups. Many species, especially true bugs, defend themselves with special glands that release bad-smelling and bad-tasting chemicals that repel their enemies. The glands open underneath or on the sides of the thorax, or midsection, of adults and on the back of the abdomen of the larvae. The smell released by these glands has given at least one group the common name "stink" bugs.

Aquatic bugs trap layers of air over parts of their bodies or capture a bubble underneath their wings so they can breathe under water. Water scorpions have long breathing tubes on the tip of their abdomen that they use like a snorkel to breath underwater. The exoskeletons, or hard outer coverings, of some aquatic hemipteran larvae are so thin that they can draw oxygen into their bodies directly from the water.

Courtship is usually brief and involves flashing legs, wings, and antennae that are brightly colored or distinctly hairy. Some species produce sounds. Male and sometimes female cicadas vibrate special plates on the sides of their bodies to produce buzzes and clicks that are attractive to potential mates. Some hoppers vibrate their bodies to send signals that travel through stems. Male water striders use their front feet to send ripples over the surface of the water to stake out territories and attract mates. Many species produce pheromones, special chemicals that are used to attract members of the opposite sex as mates.

Males usually deposit sperm directly into the female's reproductive organs. During mating the male may ride on the back of the female, or the pair will become joined at the tips of their abdomens. They may remain together only briefly or for several hours. Terrestrial species usually mate on the surfaces of plants, rocks, logs, or on the ground. Water bugs mate above or below the water surface. Under water they will perch on rocks, logs, or floating plants.

Nearly all species of true bugs must mate in order to reproduce. However, some mealy bugs and scale insects reproduce by parthenogenesis (PAR-thuh-no-JEH-nuh-sihs), a process where the young develop from unfertilized eggs. Nearly all aphids reproduce by switching back and forth between mating and parthenogenesis. In spring and fall, winged males and females mate to produce eggs that hatch into wingless females. These females reproduce by parthenogenesis, giving live birth to more wingless females. At the end of summer the wingless females lay eggs that hatch into winged males and females. Some scale insects are hermaphrodites (her-MAE-fro-daits). Hermaphrodites are individual animals that have both male and female reproductive organs. This means that any two individuals, not just a male and female, can get together to mate to produce offspring.

WHAT'S BUGGING YOU?

The word "bug" comes from the Middle English word bugge, meaning spirit or ghost. Some people use the term "bug" to describe almost any kind of insect. But ladybugs and lightningbugs are actually beetles. And pillbugs and sowbugs are not insects at all but crustaceans related to shrimp and lobsters. Entomologists, scientists who study insects, use the name "true bug" to distinguish a specific group of hemiptera from all insects and other animals.

Eggs may be laid singly or in batches on or near suitable sources of food. Parasitic bat bugs and aphids reproducing by parthenogenesis do not lay eggs and give live birth. The adults of only a few species care for their eggs or young or both. Male giant water bugs remain close to egg clusters in order to guard them. In some species of terrestrial true bugs either the males or females will stand directly over the eggs until they hatch. The larvae of true bugs and many other hemipterans usually resemble the adults but lack fully developed wings and the ability to reproduce. They develop gradually by molting, or shedding their exoskeletons, five times before reaching adulthood. Their life cycles may take just a few weeks or more than seventeen years to complete.

HEMIPTERANS AND PEOPLE

Hemipterans are used as food for both people and their pets. In parts of Mexico, humans eat egg masses of water boatmen that are fried or dried in the sun. Giant water bugs in India are cooked in syrup and are sold as an expensive treat. Female cicadas full of eggs are eaten in many countries throughout Asia. Stink bugs and their eggs are also dried and sprinkled on food like pepper.

A reddish-purple dye known as carmine comes from a scale insect that feeds on the juices of cactus. This dye is used to color fabrics and as a food coloring. The bodies of a related insect, the lac scale, are used to make shellac.

A few species of true bugs are reared by the millions and released in agricultural fields. They are used instead of pesticides to control crop pests. For example, predatory stink bugs will attack caterpillars that eat soybean plants.

Cicadas have been used to symbolize life after death in the Far East. Jade carvings of these were once put into the mouths of dead princes and other important people. Today the Chinese keep cicadas in cages to hear them sing. They also make and fly kites that look like cicadas.

Several species of hemiptera are important crop pests. They damage leaves, stems, and fruits. Some species also spread plant fungus and viruses. In South America, blood-feeding species attack humans and other wild and domestic animals, spreading Chagas disease.

CONSERVATION STATUS

Five species of hemiptera are listed by the World Conservation Union (IUCN). Two are listed as Extinct, or no longer living. Three species of cicadas are listed as Near Threatened, or likely to qualify for a threatened category in the near future. Like most other organisms, hemipteran populations are threatened by a variety of things that cause habitat loss and destruction, such as logging, development, pollution, overuse of insecticides, and the introduction of exotic species.

GREENHOUSE WHITEFLY (Trialeurodes vaporariorum): SPECIES ACCOUNTS

Physical characteristics: Greenhouse whiteflies are small insects measuring 0.06 inches (1.5 millimeters) in length. Males and females are similar in size and appearance and winged. The yellowish to pale brown body and wings are coated with a powdery white wax. Larvae are flat and yellowish.

Geographic range: They are found on all continents except Antarctica.

Habitat: They are usually found on twigs and the undersides of leaves on a wide variety of tropical plants. They are also widespread on cultivated plants in greenhouses.

Diet: Greenhouse whiteflies feed on plant sap.

Behavior and reproduction: After hatching, the larvae wander for several hours before finding a feeding site on the underside of a leaf. After piercing the leaf with their mouthparts the larvae will remain at that same spot until they reach adulthood. The exoskeleton of the last (fourth) larval stage becomes a protective case where the winged adult develops. Both adults and larvae feed in groups. The adults move about and feed at different sites and will quickly fly if disturbed.

Males and females mate all year long. The yellow eggs are attached to the leaf surface in curved rows.

Greenhouse whiteflies and people: This species is a serious pest in greenhouses. When feeding in large numbers they can weaken a plant by draining its sap. Adults and larvae produce a sticky waste product called honeydew. Sooty mold develops on the honeydew. Cultivated plants covered with black, fuzzy mold do not sell, resulting in growers losing money.

Conservation status: This species is not endangered or threatened. ∎

PEA APHID (Acyrthosiphon pisum): SPECIES ACCOUNTS

Physical characteristics: Pea aphids are small, green, insects (either with or without wings) measuring 0.08 to 0.16 inches (2 to 4 millimeters) in length. They have red eyes and threadlike antennae as long as the body. The legs are also long and slender. Wings, if present, are clear. Projections on the abdomen are long and slender. The larvae resemble small, wingless adults.

Geographic range: They are found on all continents except Antarctica.

Habitat: Pea aphids live on their food plants. They are especially fond of plants related to peas, such as alfalfa, beans, clovers, peas, and other crops.

Diet: Adults and larvae suck sap from leaves, stems, and flowers.

Behavior and reproduction: Females survive through the winter on food plants. Winged males and females appear in spring. Adults and larvae feed in dense patches on plants.

The species reproduces by parthenogenesis all year long in warmer climates. In some areas they alternate between mating and parthenogenesis.

Pea aphids and people: This species can become a pest of alfalfa crops but is usually effectively controlled by using the parasitoid (PAE-re-sih-toyd) wasp. The larvae of parasitoids feed inside the body of the host, eventually killing it.

Conservation status: This species is not endangered or threatened. ∎

SEVENTEEN-YEAR CICADA (Magicicada septendecim): SPECIES ACCOUNTS

Physical characteristics: The seventeen-year cicada (sih-KE-duh) has a plump body, dull dark brown to shiny black in color, with reddish eyes, legs, and wing veins. They measure 1.37 to 1.57 inches (35 to 40 millimeters) in length. The underside of the abdomen has broad orange bands. The antennae are very short and hairlike. Legs are short and adapted for walking. At rest, the clear wings are folded rooflike and extend beyond the abdomen. The underground larvae are nearly colorless.

Geographic range: They are found in the eastern United States, east of the Great Plains.

Habitat: They live in a canopy of deciduous trees in temperate forests and rainforests.

Diet: Cicadas suck plant sap. Adults feed from twigs, while larvae attack roots.

Behavior and reproduction: Adults are active during the day from late May through early July. Males chirp loudly to attract both males and females. Larvae feed underground, feeding on the same root for long periods of time. As they grow larger they move to thicker and thicker roots. When they are ready to become adults, they dig a tunnel upward. They emerge from the soil and crawl up a tree or fence to molt for the last time. Each population reaches adulthood about the same time, every seventeen years. However, different populations called broods will reach maturity on a different cycle.

Males call to attract females. Mating occurs on stems with the male and female connected by the tips of their abdomens. Females embed their eggs in plant stems. The larvae hatch, drop to the ground, and search for a suitably sized root to feed. The larvae resemble the adults but lack wings, have strong front legs adapted for digging, and are incapable of reproducing. They molt, or shed their exoskeletons, five times over a seventeen-year period to reach adulthood. The adults live four to six weeks.

Seventeen-year cicada and people: The appearance of thousands of cicadas every seventeen years has fascinated naturalists and scientists for more than three hundred years. If abundant in nurseries and orchards, larval feeding can be harmful to trees. Adult females in large numbers can also damage twigs by the egg-laying activities. The sound of thousands of male cicadas singing at once is annoying to many people.

Conservation status: This species is listed by the World Conservation Union (IUCN) as Near Threatened, or likely to qualify for a threatened category in the near future. They are not under immediate threat of extinction, but many populations are threatened by the removal of large numbers of trees from their habitats. ∎

GIANT WATER BUG (Lethocerus maximus): SPECIES ACCOUNTS

Physical characteristics: The giant water bug is the largest true bug in the world, with adults reaching 4.5 inches (115 millimeters) in length. The body is uniformly pale to dark grayish brown. The forelegs are large, powerful, and adapted for grasping prey. The middle and hind legs are flattened for swimming. Males and females are similar in both size and appearance. The larvae resemble the adults but are smaller and lack fully developed wings.

Geographic range: Giant water bugs are found from the West Indies south to northern Argentina.

Habitat: This species lives on submerged plants growing along the margins of pools and lakes.

Diet: They eat aquatic insects, fish, frogs, and tadpoles.

Behavior and reproduction: Giant water bugs kill their prey with digestive saliva that turns the victim's tissues into liquid. The fluid is then sucked up with short, beaklike mouthparts. They will successfully capture and kill prey that is larger than they are. Adults breathe by capturing air under their wings. Larvae rely on patches of short hairs underneath their bodies to trap a layer of air. Adults fly to different bodies of water at night and are often attracted to lights.

Clusters of dozens of eggs are laid on twigs above the water surface and are guarded by the male until they hatch. The larvae disperse at hatching.

Giant water bugs and people: Giant water bugs prey on young fish and may seriously reduce production at fish farms. Bites are very painful but infrequent.

Conservation status: This species is not endangered or threatened. ∎

BED BUG (Cimex lectularius): SPECIES ACCOUNTS

Physical characteristics: A bed bug has a body that is rusty brown to dull red, flat, oval to round when not fed, and much fatter and longer after a meal. They measure 0.16 to 0.19 inches (4 to 5 millimeters) in length. The mouthparts are short and beaklike. The antennae have four segments. The front segment of the thorax or midsection is expanded so that it surrounds the back of the head. The legs and wings of these flightless insects are short. The larvae resemble small adults.

Geographic range: Bed bugs are found on all continents, except Antarctica. They are rare or absent in large areas of Asia.

Habitat: They prefer to live in human dwellings and usually find shelter in the narrow spaces found in bedrooms, bed frames, and mattresses, or under wallpaper.

Diet: They feed on human blood but will also attack chickens, dogs, and bats.

Behavior and reproduction: Adults and larvae hide during the day and emerge at night to feed. They walk across bedding and clothing to look for sleeping people. When they find a human host they use their mouthparts to pierce the skin and suck blood from the wound. They will suck up four to five times their body weight. In cold climates they can live without food for more than a year but are unable to reproduce during this time.

Males and females mate while they are hidden in their shelters. Males use their reproductive organs to puncture the female's abdomen and place sperm in her body cavity. The sperm eventually finds its way into the female's reproductive organs. Eggs are attached to any surface on or near beds. The larvae start feeding as soon as they hatch.

Bed bugs and people: Bed bugs have been considered pests since the time of ancient Egypt and classical Greece. Their populations expand rapidly among humans living in crowded conditions. Bed bug bites are painless, but their saliva does cause itching. They can spread some parasites with their bites.

Conservation status: This species is not endangered or threatened. ∎

SEA SKATER (Halobates micans): SPECIES ACCOUNTS

Physical characteristics: The sea skater has a short, thick body, with a very short abdomen. They measure about 0.16 to 0.18 inches (4.0 to 4.6 millimeters) in length. The dull brown to black body is covered with a coat of small, silvery hairs. The head has a pair of yellow marks.

Geographic range: They are found between the latitudes 40° north and 40° south, with most species living on warm, tropical waters.

Habitat: Sea skaters live among mats of floating algae on the surface of the ocean.

Diet: Adults and larvae feed on tiny crustaceans, small fish, and floating jellyfish. Crustaceans have a soft segmented body covered by a hard shell.

Behavior and reproduction: Sea skaters move quickly on the ocean surface to find food and mates.

Males and females mate on the ocean surface. Eggs are laid in great numbers and are attached to any floating object, including feathers, seaweed, wood, or the bodies of cuttlefish. The larvae molt five times before reaching adulthood.

Sea skaters and people: Sea skaters do not affect people or their activities.

Conservation status: This species is not endangered or threatened. ∎

BACKSWIMMER (Notonecta sellata): SPECIES ACCOUNTS

Physical characteristics: The backswimmer's body is widest at the middle. The head is rounded, while the abdomen narrows at the tip. They measure 0.31 to 0.35 inches (8 to 9 millimeters) in length. Their bodies usually have dark blue and white markings, but some individuals are colorless. The mouthparts are short and cone-shaped. The front and middle legs are short. The hind legs are long, fringed with hairs, and are held away from the body and used like boat oars. The larvae closely resemble the adults but are smaller and lack wings.

Geographic range: They are found in the lowlands of southern South America from central Bolivia, Paraguay, and southern Brazil to northern Argentina, east of the Andes.

Habitat: This species prefers to live in cloudy water in shallow ponds and pools with few plants. It is often found in temporary rain pools.

Diet: They feed on all kinds of small insects and crustaceans living near the water surface.

Behavior and reproduction: Backswimmers slowly swim upside down near the water surface, searching for prey, but can move quickly when threatened. They seize prey and hold it with the front and middle legs. Winged adults escape drying ponds by flying away. They are often attracted to lights at night.

Mating takes place near the surface of the water. Eggs are glued individually to submerged twigs and algae. The larvae molt five times before reaching adulthood.

Backswimmers and people: Backswimmers may harm small fish, but they may also control mosquito larvae.

Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Books:

McGavin, G. C. Bugs of the World. London: Blandford, 1999.

Schuh, R. T., and J. A. Slater. True Bugs of the World (Hemiptera: Heteroptera): Classification and Natural History. Ithaca, NY: Cornell University Press, 1995.

Tavolacci, J., ed. Insects and Spiders of the World. Volume 2: Beetle-Carpet Beetle. Vol. 3: Carrion Beetle-Earwig. New York: Marshall Cavendish, 2003.

Periodicals:

Evans, A. V. "Dogdays Are Here Again." Fauna (July-August 2001): 58–66.

Web sites:

"Hemiptera. Bugs, Aphids, Cicadas." Ecowatch. http://www.ento.csiro.au/Ecowatch/Hemiptera/Hemiptera.htm (accessed on October 8, 2004).

Order: Homoptera. http://insectzoo.msstate.edu/Students/homoptera.html (accessed on October 8, 2004).

Periodical Cicada Page. http://insects.ummz.lsa.umich.edu/fauna/Michigan_Cicadas/Periodical/Index.html (accessed on October 8, 2004).

Scale Net. http://www.sel.barc.usda.gov/scalenet/scalenet.htm (accessed on October 8, 2004).

"True Bugs. Heteroptera." BioKids Critter Catalog. http://www.biokids.umich.edu/critters/information/Heteroptera.html (accessed on October 8, 2004).

Videos:

Bug City. Aquatic Insects. Wynnewood, PA: Schlessinger Media, 1998.