In California, there are about 200 species but fewer than a dozen are important pests. The most common ant occurring in and around the house and garden in California is the Argentine Ant, Linepithema humile (formerly Iridomyrmex humilis). Other common ant pests include the Pharoah Ant(Monomorium pharaonis), the Odorous House Ant (Tapinoma sessile), the Thief Ant (Solenopsis molesta), and the Southern Fire Ant (Solenopsis xyloni). The Velvety Tree Ant, Liometopum occidentale, nests in old wood and is a common outdoor species in landscapes.

Less common, but of great importance, is the Red Imported Fire Ant, Solenopsis invicta, which has recently gained a foothold in southern California. In some areas, the spread of the fire ant has been slowed by competition from the Argentine ant.

Carpenter Ants, Camponotus spp., also invade buildings in California. Although they do not eat wood as termites do, they hollow it out to nest and may cause considerable damage.

Ants belong to the insect order Hymenoptera and are close relatives of bees and wasps. They are familiar insects that are easily recognized, especially in their common wingless adult forms, known as workers. However, winged forms of ants, which leave the nest in large numbers in warm weather to mate and establish new colonies, are often mistaken for winged termites, which also leave their nests to mate.

Ants undergo complete metamorphosis, passing through egg, larval, pupal, and adult stages. Larvae are immobile and wormlike and do not resemble adults. Ants, like many other hymenopterans, are social insects with duties divided among different types, or castes, of adult individuals. Queens conduct the reproductive functions of a colony and are larger than other ants; they lay eggs and sometimes participate in the feeding and grooming of larvae. Female workers, who are sterile, gather food, feed and care for the larvae, build tunnels, and defend the colony; these workers make up the bulk of the colony. Males do not participate in colony activities; their sole purpose is to mate with the queens. Few in number, males are fed and cared for by workers.

Ant facts
• Ants belong to the insect order Hymenoptera and are close relatives of bees and wasps.
• More than 12,000 species occur throughout the world.
• 200 species occur in California, but fewer than a dozen are important pests.
• Ants are common pests in homes, restaurants, hospitals, and warehouses.
• Ants enter buildings seeking shelter, food, and water.
• Established ant colonies are difficult to control.

ROACHES

Cockroaches thrive in warm environments that provide food, water, and shelter. Roaches hide in cracks, crawl spaces, and other dark places during the day and come out at night to feed. Pesticide sprays alone will not control roaches and are not usually required. Baits provide better control. You must integrate several strategies to make your home a less roach-friendly environment. Thoroughness is essential for effective control.

There are six species of cockroaches in California that can become pests: German cockroach, brownbanded cockroach, oriental cockroach, smokybrown cockroach, American cockroach, and Turkestan cockroach. A seventh species, the field cockroach, is not really a pest. It is usually found outdoors, but sometimes comes indoors when it is hot or dry and is often mistaken for the German cockroach. Of these seven species, the one that has the greatest potential for becoming persistent and troublesome is the German cockroach, which prefers indoor locations. Oriental and American cockroaches occasionally pose problems in moist, humid areas.

Cockroaches contaminate food and eating utensils, destroy fabric and paper products, and impart stains and unpleasant odors to surfaces they contact.

BEES

Carpenter bees build nests in wood, creating galleries that can weaken structures; however, they rarely cause severe damage. People may be frightened by carpenter bees because of their large size, their similarity to bumble bees, and their annoying noise.

RODENT

The house mouse (Mus musculus) is one of the most troublesome and economically important rodents in the United States. House mice thrive under a variety of conditions; they are found in and around homes and commercial structures as well as in open fields and agricultural lands. House mice consume and contaminate food meant for humans, pets, livestock, or other animals. In addition, they cause considerable damage to structures and property, and they can transmit pathogens that cause diseases such as salmonellosis, a form of food poisoning.

House mice are small rodents with relatively large ears and small black eyes. They weigh about 1/2 ounce and usually are light brownish to gray in color. An adult is about 5 to 7 inches long, including the 3- to 4-inch tail.

Droppings, fresh gnaw marks, and tracks indicate areas where mice are active. Mouse nests are made from fine shredded paper or other fibrous material, usually in sheltered locations. House mice have a characteristic musky odor that identifies their presence. Mice are active mostly at night, but they can be seen occasionally during daylight hours.

While the house mouse has not been found to be a carrier of hantavirus, other mice have. Most notable are the deer mouse and the white-footed mouse, which sometimes invade cabins and outbuildings in California. The house mouse is distinguished from the deer mouse and the white-footed mouse by its overall gray-colored coat. The other two species have a white underside with a distinct line of demarcation between the dark coloration on top and the white underside. In addition, the tail on the house mouse has almost no fur on it, whereas the tails of the deer mouse and the white-footed mouse are moderately to well furred and are light underneath and dark on top.

Native to Central Asia, the house mouse arrived in North America on ships with settlers from Europe and other points of origin. A very adaptable animal, the house mouse often lives in close association with humans, along with Norway rats and roof rats; however, mice are more common and more difficult to control than rats.

Although house mice usually prefer to eat cereal grains, they are "nibblers" and will sample many different foods. Mice have keen senses of taste, hearing, smell, and touch. They are excellent climbers and can run up any rough vertical surface. They will run horizontally along wire cables or ropes and can jump up to 12 inches from the floor onto a flat surface. Mice can squeeze through openings slightly larger than 1/4 inch across. House mice frequently find their way into homes in the fall of the year, when outdoor temperatures at night become colder.

SILVER FISH

Silverfish and firebrats are nocturnal and hide during the day. If the object they are hiding beneath is moved, they will dart toward another secluded place. They come out at night to seek food and water. Both insects prefer dry food such as cereals, flour, pasta, and pet food; paper with glue or paste; sizing in paper including wallpaper; book bindings; and starch in clothing. Household dust and debris, dead insects, and certain fungi also are important sources of food. However, they can live for several months without nourishment.

Large numbers of these insects can invade new homes from surrounding wild areas, especially as these areas dry out during the summer. They also can come in on lumber, wallboard, and similar products. Freshly laid concrete and green lumber supply humidity, while wallpaper paste provides food.

The common silverfish, Lepisma saccharina, is shiny, silver or pearl gray, and about 1/2 inch long, although it can grow as long as 3/4 inch. The common firebrat, Thermobia domestica is shiny, a mottled gray or brown, and about 1/2 inch long. Adults of both species are slender, wingless, soft-bodied insects with 2 long, slender antennae. Their bodies taper gradually from front to rear to 3 long, thin, taillike appendages.

Although small nymphs (those that are less than 1/8 inch long) lack scales, both large nymphs and adults have them. If you see scales around or beneath damaged items, it is a good indication that these pests are the culprits. The scales are delicate, dustlike, and slightly incandescent in the light, and they stick to most surfaces.

Eggs of both species are about 1/25 of an inch long. The females lay the eggs in crevices, on cloth, or buried in food or dust. The average clutch contains 50 eggs, but this can vary from 1 to 200. Firebrat eggs hatch in about 14 days and silverfish eggs in about 19 to 32 days. In colder environments eggs can remain dormant for up to 6 weeks, hatching as soon as the temperature rises.

Newly hatched nymphs are about 1/16 of an inch long, plump, white, and have no scales. They acquire their scales about 12 days after their fourth molt; at that point the firebrat and silverfish look like smaller versions of the adults and gradually grow in size until they reach maturity. Unlike other insects, firebrats and silverfish molt continuously throughout their life, passing through 45 to 60 instars or development stages. Firebrats live about 2 years and silverfish about 3 years.

When the temperature is below 50°F, firebrats can take as long as 300 days and silverfish as long as 500 days to develop into adults. When it is above 75°F, it can take firebrats as few as 40 days and silverfish as little as 60 days to develop into adults.

FLIES

Of the thousands of species of flies, only a few are common pests in and around the home. Some of the more common nuisance flies are the house fly (Musca domestica), the face fly (Musca autumnalis), the stable fly (Stomoxys calcitrans), the little house fly (Fannia canicularis), and several species of garbage fly (especially in the genus Phaenicia). These pests breed in animal wastes and decaying organic material from which they can pick up bacteria and viruses that may cause human diseases. In addition, adult stable flies (sometimes called "biting flies") feed on mammalian blood and can give a painful bite.

All flies undergo complete complete metamorphosis with egg, larva, pupa, and adult stages in their development. The female fly deposits her eggs in animal waste or moist organic material where the larvae, or "maggots," complete their development, feeding on bacteria associated with their developmental site. When the maggots have completed their development and are ready to undergo the next step in their metamorphosis, they convert their last larval skin into a puparium, a hardened shell within which the pupa develops. Within the puparium, the pupa transforms into an adult fly, which pops off the end of the puparium and emerges. Body fluids pump into the fly’s veins, causing the wings to unfold and expand and allowing them to dry and harden so that the adult can fly. The rate of fly development is dependent upon temperature, and under optimal summertime conditions flies may develop from egg to adult in as little as 7 days. Once the female fly has mated, she can lay several batches of eggs, typically containing over 100 eggs each.

While humans commonly find adult flies to be the most bothersome, the larval stage should be the prime target for control efforts. Elimination of larval habitat is the preferred method of pest fly suppression. By removing material in which the larvae develop, the life cycle of the fly can be broken, preventing subsequent production of adult flies. While chemical pesticides may be effective for suppressing adult fly populations in some situations, they are not a substitute for proper sanitation and aggressive elimination of nuisance fly developmental sites. Because flies can quickly develop resistance to insecticides, use them only as a last resort to obtain immediate control of adult flies.

WASPS

Only a few of the very large number of wasp species in California live a social life; these species are referred to as social wasps. Some social wasps are predators for most or all of the year and provide a great benefit by killing large numbers of plant-feeding insects and nuisance flies; others are exclusively scavengers. Wasps become a problem only when they threaten to sting humans. One of the most troublesome of the social wasps is the yellowjacket.

In western states there are two distinct types of social wasps: yellowjackets and paper wasps. Yellowjackets are by far the most troublesome group. Paper wasps are much less defensive and rarely sting humans. They tend to shy away from human activity except when their nests are located near doors, windows, or other high traffic areas.

Nests of both yellowjacket and paper wasps typically are begun in spring by a single queen who overwinters and becomes active when the weather warms. She emerges in late winter/early spring to feed and start a new nest. From spring to midsummer nests are in the growth phase, and the larvae require large amounts of protein. Workers forage mainly for protein at this time (usually in the form of other insects) and for some sugars. By late summer, however, the colonies grow more slowly or cease growth and require large amounts of sugar to maintain the queen and workers. So foraging wasps are particularly interested in sweet things at this time.

Normally, yellowjacket and paper wasp colonies only live one season. In very mild winters or in coastal California south of San Francisco, however, some yellowjacket colonies survive for several years and become quite large.

The term yellowjacket refers to a number of different species of wasps in the genera Vespula and Dolichovespula (family Vespidae). Included in this group of ground-nesting species are the western yellowjacket, Vespula pensylvanica, which is the most commonly encountered species and is sometimes called the "meat bee," and seven other species of Vespula. Vespula vulgaris is common in rotted tree stumps at higher elevations and V. germanica (the German yellowjacket) is becoming more common in many urban areas of California, where it frequently nests in houses. These wasps tend to be medium sized and black with jagged bands of bright yellow (or white in the case of the aerial-nesting Dolichovespula [=Vespula] maculata) on the abdomen, and have a very short, narrow waist (the area where the thorax attaches to the abdomen).

Nests are commonly built in rodent burrows, but other protected cavities, like voids in walls and ceilings of houses, sometimes are selected as nesting sites. Colonies, which are begun each spring by a single reproductive female, can reach populations of between 1,500 and 15,000 individuals, depending on the species. The wasps build a nest of paper made from fibers scraped from wood mixed with saliva. It is built as multiple tiers of vertical cells, similar to nests of paper wasps, but enclosed by a paper envelope around the outside that usually contains a single entrance hole. If the rodent hole is not spacious enough, yellowjackets will increase the size by moistening the soil and digging. Similar behavior inside a house sometimes leads to a wet patch that develops into a hole in a wall or ceiling.

Immature yellowjackets are white, grublike larvae that become white pupae. The pupae develop adult coloring just before they emerge as adult wasps. Immatures are not normally seen unless the nest is torn open or a sudden loss of adult caretakers leads to an exodus of starving larvae.

Aerial-nesting yellowjackets, Dolichovespula arenaria and D. maculata, build paper nests that are attached to the eaves of a building or are hanging from the limb of a tree. The entrance is normally a hole at the bottom of the nest. These aerial nesters do not become scavengers at the end of the season, but they are extremely defensive when their nests are disturbed. Defending D. arenaria sometimes bite and/or sting, simultaneously. Wasp stingers have no barbs and can be used repeatedly, especially when the wasp gets inside clothing. As with any stinging incident, it is best to leave the area of the nest site as quickly as possible if wasps start stinging.

Paper wasps such as Polistes fuscatus aurifer, P. apachus, and P. dominulus are large (1-inch long), slender wasps with long legs and a distinct, slender waist. Background colors vary, but most western species tend to be golden brown, or darker, with large patches of yellow or red. Preferring to live in or near orchards or vineyards, they hang their paper nests in protected areas, such as under eaves, in attics, or under tree branches or vines. Each nest hangs like an open umbrella from a pedicel (stalk) and has open cells that can be seen from beneath the nest. White, legless, grublike larvae sometimes can be seen from below. Paper wasp nests rarely exceed the size of an outstretched hand and populations vary between 15 to 200 individuals. Most species are relatively unaggressive, but they can be a problem when they nest over doorways or in other areas of human activity, such as fruit trees.

FLEAS

Cat fleas, Ctenocephalides felis, are the most common ectoparasite on domestic cats and dogs. Dog fleas, C. canis, look like cat fleas but are rare in California. Sticktight fleas, Echidnophaga gallinacea, are commonly found on ground squirrels and poultry; the females firmly attach themselves along the ears and eyes of their host. They can become a problem with pets that roam. The ground squirrel flea, Oropsylla montana, is found on ground squirrels and is the vector of sylvatic plague in California. However, fleas on cats or dogs in California most likely are cat fleas.

IDENTIFICATION

Adult fleas are no larger than 1/8 inch long, so it is difficult to see a number of the characteristics used to describe them. These reddish-brown, wingless insects are laterally compressed, so they look as if they are walking on edge. Cat fleas have both pronotal and genal combs. They have piercing-sucking mouthparts through which they obtain blood meals from their hosts.

Unlike most fleas, adult cat fleas remain on the host where feeding, mating, and egg laying occur. Females lay about 20 to 50 eggs per day. Cat flea eggs are pearly white, oval, and about 1/32 inch long. The eggs are smooth and readily fall from the pet and land on surfaces such as bedding and carpeting in the animal’s environment. They hatch in about 2 to 5 days.

Flea larvae are no larger than 3/16 inch long, hairy, and wormlike with a distinct, brownish head but no eyes or legs. The larvae feed on dried blood and excrement adult fleas produce while feeding on the pet. Larval development is restricted to protected places where there is at least 75% relative humidity. The larvae feed and crawl around for 8 to 15 days before building small, silken cocoons in which they pupate and develop into adults. Debris, such as pet hair or skin or carpet fibers, usually covers the pupae, providing visual camouflage.

Flea larvae develop more quickly at higher temperatures, preferring areas that are 70° to 90°F. At cool temperatures, fully formed fleas can remain in their cocoons for up to 12 months. Warm temperatures and mechanical pressure caused by walking on or vacuuming carpet stimulate emergence from the cocoon. At normal room temperatures, the entire life cycle can occur in about 18 days.

An adult cat flea generally lives about 30 to 40 days on the host. When normal grooming activity is restricted, 85% of adult females survived for 50 days. You can find fleas on pets throughout the year, but numbers tend to increase dramatically during spring and early summer when conditions favor larval development.