Adult Fleas are 1/16 – 1/8 inch long and dark brown with compressed bodies; their back legs are modified for jumping. The cat flea is the most common flea species. Fleas lay their eggs on the host animal; but they soon fall off and tiny, white, legless, flea larvae emerge to scavenge on debris, typically near where the host spends most of its time. After pupation, adult fleas emerge and seek a host–typically a pet, but sometimes a human. Large infestations can cause significant discomfort for people and pets.
Sowbugs are oval, gray insects about 1/2 inch long; they have seven pairs of legs. The related pillbug looks very similar but, unlike the sowbug, a pillbug can roll itself into a ball. Sowbugs (and pillbugs) prefer moist areas and are commonly found under objects lying on the ground (stones, logs, etc.). They occasionally move into damp basements and crawlspaces.
Adult brown-banded cockroaches are approximately 1/2 long. Their bodies are golden brown with pale brown horizontal bands that run across their wings. Adult males can fly, but females cannot. Nymphs appear similar to adults, with the characteristic brown bans running across their bodies. Brown-banded cockroaches prefer warm locations above 80 degrees and are less dependent on water than other cockroaches species. As a result, they typically are found on walls, behind door moldings and picture frames, and in furniture casings, appliances, etc. Females glue their eggs in such locations.
The American cockroach is a large, reddish-brown species ranging from 1 1/2 – 2 inches long. Adults are weak flyers that rarely take off from the ground. American cockroaches typically do not inhabit living quarter in homes and other buildings. They prefer sewer systems, steam tunnels, and pipe and utility chases beneath commercial buildings.
Adult German cockroaches are medium brown and approximately 1/2 inch long. They are distinguished from other roaches by two dark, longitudinal stripes directly behind the head. Adults don not fly. Nymphs are smaller and darker than adults, with a single light stripe running down the back. German cockroaches reproduce quicker than other common pest cockroaches species, and their nymph survival rate is higher because females carry their egg cases until shortly before hatching, then drop them in suitable locations.
Oriental cockroaches are approximately 1 1/4 inches long and are dark brown to shiny black. They do not fly. The wings of adult males cover 75 percent of the abdomen, and females possess only rudimentary wings. Oriental cockroaches prefer cool, damp locations such as basements and crawl spaces; during the warm months, they can be found outdoors.
Asian Lady Beetles
Asian lady beetles are small, round insects less than 1/2 inch long. They vary from red to yellow, with or without black spots. A black mark in the shape of the letter M, behind the head, clearly identifies this beetle. Asian lady beetles become a nuisance in the fall when they congregate in and around buildings, looking for shelter. They can become a nuisance again when they emerge from their hiding places during the first warm days of spring.
Bedbugs are approximately 1/4 inch in length, reddish-brown, with flattened, oval bodies. The Common bedbug emerges at night to feed on its host. During the day, bedbugs hide in cracks and crevices near the host bedding. Bedbugs are not believed to be important in the transmission of diseases to peoples, but their bite may produce an allergic reaction, cause swelling, itching, etc.
Springtails are tiny, white or gray insects approximately 5/100 inch long. They have a forked appendage at the rear of their abdomen, which propels them into the air when disturbed. Springtails inhabit soil containing decaying plant material. They require high humidity for survival. Springtails become pests when they invade buildings in large numbers. They are commonly found underneath potted plants.
The bald-faced hornet is 3/4 inch long, with black and white markings including a white face. Its nest are papery oval structures that typically hang from tree limbs and sometimes buildings.
Bumble bees are 1/2 – 1 inch long, hairy, yellow and black insects that nest in the ground. Colony size is small compared to honey bees; only a few hundred individuals.
Carpenter bees are solitary insects. They resemble bumble bees, but have a shiny black abdomen. Carpenter bees excavate galleries in wood, where they lay their eggs. The entrance hole is approximately 1/2 inch in diameter. The tunnel extends into the wood for only a short distance before turning with the grain. Male carpenter bees aggressively defend nest sites, but only the female can sting.
The European hornet is almost 1 1/2 inches long. It is brown with dull reddish stripes. The European hornet is a woodland species that usually nest in hollow tree trunks, but sometimes in wall voids and attics.
Honey bees are 1/2 inch long, hairy, and golden brown and black. Their colonies, unlike those of other bees and wasps, can persist for several years. They typically nest outdoors, but sometimes nest contain a single queen, numerous sterile female workers, and drones (males). In contrast with other bees and wasp, honey bees can sting only once, leaving their stingers in their victims.
Yellowjackets are a stinging pest whose colonies can include several thousand individual by late summer. Yellowjackets are boldly marked in yellow and black, with a striped abdomen. They are approximately 1/2 long. Their nest is located underground or in structural voids, depending on the species. Yellowjackets pose a serious threat to people because of their large colonies and aggressive nature in defense of the nest.
Paper wasps are typically 3/4 inch long and reddish-brown. They build umbrella nests with hexagonal cells, open at one end. Nests often are located beneath roof eaves and overhangs. Note that European paper wasps are black and yellow and have a habit of nesting in small structural voids.
Mud daubers are slender, solitary wasp about 3/4 inch long. One common species is a dark brown with yellow markings. Mud daubers build tube-shaped nest of mud that typically are attached to the sides of structures.
Cicada killers, a species of digger wasp, are large, solitary insects approximately 1 1/2 inches long. They are predominantly black with yellow markings on the abdomen. Cicada killers nest in small burrows in the soil. Males guard the nest but are incapable of stinging.
Brown Recluse Spiders
The brown recluse spider is light brown with a distinctive fiddle-shaped mark on its back. It is a long legged spider with a body length of about 1/2 inch. The brown recluse remains secluded during the day, emerging at night to search for insect prey. The brown recluse is poisonous. Victims sometimes experience serious tissue damage around the bite, but the bites are rare.
Black Widow Spiders
The adult female black widow spider is readily identified by her shiny black color and rounded abdomen with a red hourglass marking on the underside. Her body is about 1/2 inch long. The male is smaller and nondescript. Female black widows construct irregular webs in undisturbed locations, often around building foundations, woodpiles, etc. The black widow bite is poisonous and can cause severe pain around the wound, dizziness, breathing difficulties, blurred vision and nausea.
Yellow Sac Spiders
Yellow Sac spiders are small, with a body size of approximately 3/8 inch and front legs that are noticeably longer than the rest. The yellow sac spider is generally straw colored. It is active at night, entering buildings in search of prey–especially when temperatures begin to drop in the fall. Sac spiders construct silken tubes in sheltered areas where they retreat during the day. They are a mildly venomous spider.
Wolf Spiders are large, hairy spiders almost an inch long. They are colored in various patterns of gray, brown, and black. Wolf spiders are active hunters that sometimes wander into buildings. Wolf spider will bite, but are not venomous.
Cellar spiders are pale with long slender legs. Their body length is about 1/4. They spin irregular-shaped webs in dark, damp locations.
The house cricket and field cricket are two of the most common crickets found indoors. House crickets are about 3/4 inch long and light yellowish-brown with three dark brown bands on their head. The field cricket is approximately 1 inch long, robust, and dark brown or black. Crickets are a nuisance because of their nighttime chirping and because they feed on a variety of foods; they also damage fabrics and paper.
Centipedes have one pair of legs per body segment. The house centipede is brown and has long, spindly, legs, and it can grow to a length of 1 1/2 inches. This common structure-infesting pest prefers basements, crawlspaces, and other damp dark spaces. House centipedes disturb building occupants primarily because of their size and rapid movement. They can bite, but it usually causes only minor discomfort.
Silverfish and Firebrats
Silverfish and firebrats are flat, elongated insects, 1/2 – 3/4 inch long. Silverfish are silvery gray, while firebrats are gray with dark markings. Both have long antennae and three long bristles at the tip of the abdomen; and both are attracted to flour and starches and can damage paper, bookbindings, and fabrics. Silverfish and firebrats are found in damp locations. Firebrats require warmer temperatures than silverfish and tolerate drier conditions.
Adult boxelder bugs are 1/2 inch long and dark brown to black with distinctive red markings on their backs. Nymphs look similar to the adults, but lack of wings. Boxelder bugs feed on a variety of trees, preferring boxelder. They sometimes enter structures in the fall, looking for a place to overwinter. Boxelder bugs don not bite or sting; but they can become a nuisance, especially when they move inside in large numbers.
Common House Spiders
The common house spider is gray to brown with several dark stripes on its rounded abdomen. Its body is about 1/3 inch long. House spiders construct irregular-shaped webs in secluded, humid locations. They typically are found in basements and crawl spaces.
Source: Purdue University – Purdue Extension PPP-7A Category 7A Industrial, Institutional, Structural and Health Related Pest Management. Indiana Commercial Pesticide Applicator Training Manual. Purdue Agriculture Rev 7/10