Argentine Ant Linepithema humile Single-node (no stinger); All members of an Argentine Ant colony are uniformly brown in color; workers are 1/8" in length and emit a musty odor when crushed. These ants tend to displace native species upon which native flora and fauna depend. In addition they tend honeydew secreting plant pests such as aphids and scale insects. As an Argentine Ant colony moves its members can pick up various pathogens on their feet and transfer them to other surfaces such as counter tops, food and eating utensils. All members of this species are genetically similar and cooperation between individual colonies is the rule. It is thought that all Argentine ant colonies worldwide actually comprise one massive global super colony.

Carpenter Ant Camponotus modoc has a single-node (no stinger) Black in color, Workers 1/4" to 1/2" length. In California they are common in the foothills and higher elevations of the Sierra Nevada Mountains. This species does not eat wood but hollows out galleries within it as nesting places. Over time, as a colony grows, the damage can become significant. If a colony is identified control measures should be taken as soon as possible.

Carpenter Ant Camponotus vicinus Single-node (no stinger) Varies in color. Usually red & black, Workers vary from 1/8" to 3/8" length. Found in the lower elevations of east central California, this species habits are similar to those of C. modoc. Control measures should be taken if it is found infesting a structure or wood near any structure containing wood components.

Western Harvester Ant Pogonomyrmex occidentalis (Cresson) Single-node (no stinger) Workers 7-10 mm long, Color, orange to brown. Harvester Ants build gravel-covered mounds, with the entrances to the nest being on the sides and base of the mound. Harvesters are aggressive, readily defending their colonies.

Odorous House Ant Tapinoma sessile It possesses a single node (no stinger). Workers 1/8" long, color Black, emits "rotten coconut" odor when crushed. These non-aggressive scavengers will eat almost any human food and will readily nest inside homes and other structures. Like Argentine Ants, these insects will also tend aphids and consume the honeydew secreted by them.

Pavement Ant Tetramorium casespitum Two-nodes (possesses stinger) Workers 3.25 mm length, Color dark brown. This European native arrived on the North American continent in the 18th century. It gains its name from its habit of building nests in paved areas. It will also build nests in dry, bare soil conditions, dying out if vegetation becomes too dense. It feeds mainly on the dead carcasses of insects and other arthropods. Mainly a nuisance pest when it enters human structures.

Pharaoh Ant Monomorium pharaonis Two-nodes (possesses stinger) Workers 1/16" long, Color almost transparent light yellow to reddish brown with darker abdomen. Found on every continent except Antarctica, this species is almost exclusively lives in human habitations. The only exception being that it will live outdoors in tropical and subtropical climates. Spraying to control this pest will cause it to split the colony in a process called budding, actually making the problem worse. Baiting is the preferred control method.

Thief Ant Solenopsis molesta Two-nodes (possesses stinger), Workers 1/32" to 1/8" long, Color yellowish to brownish. This hardy ant can live just about anywhere, including buildings inhabited by humans. Because of their small size they can easily penetrate food wrappers. They will eat just about anything, including dead animal carcasses, making them a potential source of human disease pathogens.

Bats Most bat species are important predators that control insect populations in North America. California is home to a number of resident and migratory species. While bats are protected by law, because of their potential as disease vectors (rabies being the most concerning), they must be excluded from structures inhabited by humans.

Feral Pigeon, aka. Rock Dove, Columba livia Indigenous to the Mediterranean, it was introduced into North America. This species is a carrier of up to 50 pathogens that affect humans including Salmonella and Histoplasmosis. Their unsightly, caustic feces are responsible for extensive damage to structures and even marble statuary. Control of these birds is most successfully accomplished by the use of exclusion devices such as spikes, tension wires, netting and shock strips.

House Sparrow aka English Sparrow, Passer domesticus, is an invasive non-native species from Europe. It can now be found throughout the United States wherever humans live and work. Unfortunately this bird has a tendency to displace native cavity nesting species. The Western Bluebird is an example of a species that has suffered greatly from the House Sparrow's habits.

House Centipede, Scutigera coleoptrata; As its name suggests, this arthropod is frequently found in homes. About 1 & ¼" length, its color varies from black to brown to yellow or white. Having 15 pairs of banded legs, it is a fast runner. This predator of other insects possesses strong mandibles and will bite in self defense.

Millipedes in northern California vary greatly in size and color. All have 2 to 3 legs per segment, unlike centipedes, which have only one pair, and their bodies are more cylindrical. They feed on decaying organic matter and do not bite. They prefer cool moist conditions and usually dehydrate and die inside climate controlled structures.

Scorpion, A few species of small, honey-colored to dark brown species occur in northern California. All of them sting. None of these species present a serious threat to humans.

American Cockroach Periplaneta americana 1" to 1 1/2" long, Reddish Brown, fully developed wings, adult males capable of limited flight. Commonly found outdoors in milder climates, in cooler northern climates they are most commonly found in sewers, under thick layers of leaf litter and in ground covers. They are only occasional invaders in homes and businesses.

Brownbanded Cockroach Supella longipalpa Light brown color, brown bands across abdomen. 1/2' long with fully developed wings, adult males readily fly when disturbed. This species has an affinity for electronic devices and higher locations in structures.

German Cockroach Blatella germanica 1/2" to 5/8" long, Tan to light brown, 2 dark lines behind head. The adults have fully developed wings but do not fly. German cockroaches are the species most commonly found indoors, preferring warm, moist, protected locations near food sources.

Oriental Cockroach Blatella orientalis (Linnaeus) - The adults of this species are 1" long with dark brown to black coloration. The females are wingless. The winged males do not fly. This is the filthiest of all cockroaches. As with the American Cockroach, this species is found most often in cool, moist areas like sewers and will also survive in leaf litter and thick ground cover outdoors. They are only occasional invaders of homes and businesses.

Deer Mouse Peromyscus maniculatus, Body 3"-4" in length, not including tail, large eyes & ears, white to black fur, with white underside. This native or North America is a vector of the deadly Hantavirus. The disease is contracted by inhaling the dust of its feces. Cleanup should be done by a professional.

House Mouse Mus musculus, 5-7" long including tail, color varies– white to grey and light brown to black. This mouse, as its name suggests, is commonly found in homes and businesses. It has a small range, generally foraging for food and water within 30 feet of its nest.

Norway Rat Rattus norvegicus, up to 10" long, not including its slightly shorter tail. It has a blunt nose, short ears, grey to brown coloration. The Norway rat prefers low places and commonly constructs burrows underground beneath piles of debris. In homes it prefers the lower floors, crawl spaces and basements. It is responsible for the spread of multiple human pathogens and should not be allowed to remain in structures used by humans.

Roof Rat Rattus rattus is 12.75–18.25 long, including tail, light brown to black in color, pointed nose and large ears. Its tail is longer than its body. This agile and acrobatic rodent prefers high locations such as palm trees and attics in which to live and nest. In homes it tends to stay in high places such as attics, but will move around in a structure when foraging. As with the Norway Rat, this rodent is responsible for the spread of multiple diseases and will chew through plastic plumbing or wiring in an effort to wear down it's ever-growing incisors. Rats are frequently responsible for fires and floods in homes and other structures. Rats also cause extensive damage to cars and other motor vehicles when gnawing on wires and hoses or when nesting in engine compartments of stored vehicles.

Cat Flea Ctenocephalides felis; This is the most common flea on domestic pets. The adult cat flea is 1-2 mm long, reddish brown color. It will feed on the blood of humans.

Rat Flea Xenopsylla cheopis; The adults are 2.5 mm long and reddish brown in color. They feed primarily on rats and sometimes on humans. It is thought to be a vector of the black (or Bubonic) Plague.

TICKS, Order Ixodida

There are hundreds of species of ticks worldwide, both soft and hard bodied that feed on animal blood. They vary widely in color and size. They are responsible for several diseases: Lyme disease, Q fever, Colorado Tick Fever, Rocky Mountain spotted fever, Tularemia, Tick-borne Relapsing Fever, Babesiosis, Ehrlichiosis, Tick Paralysis and Tick-borne Meningoencephalitis, as well as Bovine Anaplasmosis.

FLIES

Bottle Flies 1/4" to 3/8" length, metallic blue, bronze or green coloration. Feed on decaying organic matter especially animal flesh. Bottle flies are important transmitters of human diseases.

Drain Flies Psychoda, 1/4" length, fuzzy appearance due to numerous hairs on body and wings, weak fliers, grey to black color, feed on and breed in organic drain sludge. Control is gained by cleaning drains of the organic material and sludge that frequently accumulates in them. Drain flies are of particular concern in food service establishments where floor drains tend to accumulate grease and other organic matter.

House Fly Musca domestica 8-12 mm long, compound red eyes, grey thorax, 4 longitudinal lines on back, hairs covering body. The House fly will feed on a wide variety of decaying organics. It is known for spreading human disease pathogens.

Phorid Flies Phoridae, (Approx 4,000 species globally) 1/2-6mm length, yellowish to black in color, hump-backed profile similar to fruit flies. Most of these feed on organic matter and fungi.

HORNETS & WASPS

Baldfaced Hornet Dolichovespula maculata is a black and white, heavy-bodied wasp, 1/2" to 1" length, distinctive white markings on face. This wasp is aggressive in nature, second only to its cousin, the Yellow Jacket. It will defend its nest vigorously if threatened. Steer clear of its nest.

European Paper Wasp Polistes dominula is an exotic invader. It has yellow and black stripes, similar to yellow Jacket but with narrower waist and longer hind legs. It is believed to be out-competing native paper wasps. This mildly aggressive insect will defend its nest.

Mud Dauber Wasp, Sceliphron caimentarium; This solitary species has a long slender body with a thread-like waist.  Its colors are reddish-brown to black with yellow markings on its thorax, abdomen and legs.This species is known for making a mud tube nest, usually consisting of 1 to 3 tubes in which the female lays her eggs.  After the eggs are laid she finds and paralyzes a spider for each one, stuffing it in the tube, which she seals with more mud.  The spiders are food for the larvae to feed on after they hatch.  This is the extent of the paper wasps parenting skills.  She moves on, leaving the young to fend for themselves.  The species is very docile.  It is reluctant to sting and will usually only do so when necessary to defend itself.

Northern Paper Wasp Polistes fuscatus is a beneficial native insect.  This North American native feeds on caterpillars.  It is 3/4” to 1” long with a slender, narrow waist, long legs and it is reddish-orange to dark brown or black with a little yellow in color.  This fairly docile species is slow to defend its nest. 

Yellow Jacket Dolichovespula arenaria; This species sportsBlack and yellow stripes.  The workers are 1/2” long (queen 3/4”).  Yellow Jackets are very aggressive in defending it their nests.  They are strong, fast fliers.  Paper nests are built in cavities in attics or walls and under-ground.  Anyone who has stumbled across a Yellow Jacket nest knows that its reputation is well earned.

SPIDERS

Black Widow (Western) Latrodectus hesperus, (Female pictured.)This species is highly venomous.  The female is 14-16 mm length(size of a quarter), having a shiny black color, red hourglass marking on bottom of her abdomen (sometimes absent).  The bite of the female presents a health hazard and can be excruciatingly painful, although the bite may go unnoticed at first.  Persons with compromised immune systems, hypertension and the very young are most vulnerable.  Anyone bitten by a female black widow should seek immediate medical attention.

Calisoga Spider (aka. False Tarantula or Funnel Web Tarantula) Calisoga longitarsis, Brown to silver color, velvety pubescence (similar to Tarantula hairs but finer} Tarantula-like in appearance and behavior but smaller in size, about 2.5” to 3” length.  When it feels threatened it will rear up, exposing its fangs much like a taratnula.  It will use its painful bite in self defense but is non-poisonous.

Cellar Spider (aka Daddy Longlegs or Skull Spider) Pholcus phalangioides, tan color, 7 cm leg span.  Contrary to urban legend this spider’s venom has not been tested or demonstrated to be “the most potent.”  Though creepy in appearance, this spider is harmless to humans.

Jumping Spiders; Several species of this fascinating spider occur in California. They display varying colors and markings. They are known for jumping up to 50 times their body length. Bites from these spiders are painful, cause redness and swelling. In some persons fever and muscle aches may result from being bitten.

Hobo Spider, Tegenaria agrestis; This spider originates from the UK and is an exotic (non-native) species in US.  Positive identification requires microscopic examination and is best done by an Arachnidologist.  It is commonly found in the Pacific Northwest and rare, but increasing, in northern California.  Its bite can cause necrotic lesions.

STORED PRODUCT PESTS

Angoumois Grain Moth Cototroga cerealella (Olivier - The adult of this species is Yellowish-brown to Grey, 1/2” wingspan.  The larval stage infests and feeds on whole grains such as dried corn, rice, and wheat. 

Cigarette Beetle Lasioderma serricorne is a reddish-brown beetle with 1/8” long, serrated, 3 Segmented Antennae.  Larvae feed on plant and animal based foodstuffs as well as non-food items, such as tobacco.  Long associated with humans.  Some were found in dried resin in Egyptian Pharaoh Tutankhamun’s tomb.

Confused Flour Beetle Tribolium confusum - The adult is reddish-brown color, 1/8 to 1/4” length, with four-clubbed antennae.  Each club increases in size as viewed from the base, outward.  The larvae can be found feeding on broken grain, grain dust, and other food items like flour, rice, dried fruit, nuts, and dried legumes such as beans and peas.  They do not feed on whole grain products.

Drugstore Beetle Stegobium paniceum, Reddish Brown Color, Adult up to 3.5 mm in length.  3 segmented antennae, grooved elytra, Wide variety of foods from pharmaceuticals to grain products.  They are sometimes are called the kitchen sink beetle because they feed on nearly everything.

Indian Meal Moth Plodia interpunctella – The moth is 8-10 mm Long, tan & brown to tan & copper color.  It has an erratic flight pattern.  The larvae feed on grains, dried fruits, nuts and other plant materials.  Sometimes all four stages of this moth’s life cycle can be found in a package.  Occasionally a package of product can be found with multiple generations of this insect, which apparently does not need to fly in order to reproduce.

Larder Beetle Dermestes lardarius, Adults brown with lighter band across wing covers.  Both adults and larvae eat high protein foods, preferring animal products.

Lesser Grain Borer Rhyzopertha dominica, Adults0.1” long, brown to black.  Cylindrical shape with pits on wing covers.   Both larvae and adults feed on wheat corn rice & millet.

Rice Weevil Sitophilus oryzae Adults 1/8” length, Reddish-Brown, 4 yellow or reddish spots on wing covers.  Slender snout;   Adults & larvae eat whole grains.  They will infest beans, birdseed, sunflower seeds and dried corn.   On occasion they can be found in pasta such as macaroni and spaghetti.

Sawtooth Grain Beetle Oryzaephilus surinamensis (Linnaeus) (top) and Merchant Grain Beetle Oryzaephilus mercator (Fauvel) (lower)Both Flattened, reddish-brown 1/10” long with 6 “sawtooth” projections on each side of the thorax.  The eyes of surinamensis are exposed and the eyes of Mercator are exposed.  Both species (adults and larvae) feed on separated and fine food particles of a wide variety of dried plant materials.

Varied Carpet Beetle Anthrenus verbasci - The adults are 3mm long, mottled orange, white & black color.  Larvae feed on natural fibers such as wool, cotton, silk, etcetera.  They will also feed on other keratin sources like discarded human and domestic animal hair and fur.  The adults feed on flower nectar.

Webbing Clothes Moth Tineola biselliella; The adult moths are 1-2 cm long with a silvery grey color.  Its wings have feathered edges.  Larvae cause extensive damage to natural fibers.  Telltale webbing tunnels and fecal droppings from larvae often present in damaged areas.  Larvae often pupate in food source.  The adults prefer dark places and are not attracted to light sources.

Yellow Mealworm aka Darkling Beetle Tenebrio molitor;  The adults are polished brown, 1/2” long, thorax finely punctured, wing covers striated.  The larvae can cause serious damage to whole grain stores.

SILVERFISH & FIREBRATS

Firebrat Thermobia domestica,  aka. Thermophilia furmorum   Similar to Silverfish but smaller at 1-1.5 cm in length.  It has darker colors than the Silverfish with longer cerci.  It prefers warmer temperatures but has the same food preferences.   It will also feed on some proteins, such as those found in pet foods. 

Silverfish Lepisma saccarina Adults 1/2 to 1” long, silver-gray appearance.  Body tapers to tail with 3 hair-like cerci at the end of the body.  It feeds on carbohydrates, such as those contained in book glue.

WOOD DESTROYERS

Powder Post Beetle Lyctoxylon dentatum;  This insect causes extensive damage to hardwoods  The adult beetle is 1/8” long, reddish to brown color.  Adults are seldom seen.  Larvae feed mainly on hardwood.  Infested wood has small holes where the adults emerge from pupation.  Identification is made by the presence of these holes and the powdery feces and wood fragments that fall from the holes.  The larval stage can last up to 10 years.

Termites   Collectively, termites are responsible for billions of dollars in damage every year, across the US.  3 species are present in California:
Pacific Dampwood Termite Zootermopsis augusticollis;  This species of termite feeds almost exclusively on damp and decaying wood and is generally not damaging to structures.
Western Drywood Termite Incisitermes minor; This species is an important pest because it does not need any moisture to survive.  If you live in an old home or by the coast, make sure you have it checked by a licensed Inspector. They are responsible for over 250 million in damage and treatment costs to California structures annually.
Western Subterranean Termite Reticulitermes hesperus   This is the most concerning species present in California.  Its colonies live in soil, feed on wood and build tunnels to gain access to our structures.  It causes the most extensive damage to our structures containing wood and other cellulose.

VERTEBRATES (BURROWING)

California Ground Squirrel Spermophilus beechey Fur mottled with mixture of dusky, light brown and gray hairs with the underside white or yellowish.  This mammal creates large open burrows which can be hazardous to humans and domestic animals sometimes undermining building foundations and other structures.

California Vole (aka. Meadow Mouse) Microtus californicus   Up to 8” length, compact body, short, furry tail.  Color varies from gray to brown or black. It burrows among and feeds on the roots & crowns of ornamental plants and creates long trails through turf.  In some years its populations can be up to 1,000 animals per acre.

Mole Scapanus spp.  Various subspecies exist, differing in size and coloration.  All burrow through soil in search of their prey which are grubs, insects and worms.  Moles create mounded burrow entrances that are round with a plug in the center.

Western Pocket Gopher Thomomys bottae;  Growing to about 8 inches long including tail, grayish to brown color.  Feeds mainly on plant roots, bulbs and fleshy portions of plants, sometimes stems & leaves near burrow.  The entrance to a gopher burrow is a roughly horseshoe shaped mound, with an off-center earthen plug.  These solitary and highly territorial animals will defend their homes aggressively, killing an opponent if necessary.

WILD ANIMAL PESTS

Opossum Didelphus virginiana is the only true marsupial in North America.  It can cause significant damage when it invades structures and can spread important parasites and human pathogens.

Raccoon Procyon lotor can cause significant damage to structures which it often invades to create a den for rearing its young.  It can also spread important parasites and human pathogens.  The species has been known attack and kill household cats and small dogs.

Striped Skunk Mephitus mephitis;  This skunk is known to burrow under homes and other structures.  Its strong odor makes it an unwelcome guest.  Trapping is the preferred method of removal.

Western Gray Squirrel Sciurus griseus, also non-nativeEastern Gray Squirrel S. carolinensis and Fox Squirrel S. niger;  All are damaging to structures.  Control of these tree dwelling rodents is mainly by exclusion and to a lesser degree, trapping.  The Western Gray is protected by law in California.

MISCELLANEOUS

Bed Bug Cimex lectularius Apple seed sized adults reddish to brown, flat profile, oval from above.  Eggs cream-colored, nymphs nearly clear at first and darken as they mature.  Cimex is an important parasite of humans.  Present in most human civilizations throughout our history.  Its feeding can cause red, swollen spots and intense itching.  This bug is expert at developing resistance to pesticides by altering its DNA.  It is not known to act as a disease vector.

Brown Marmorated Stink Bug Halyomorpha Halys   This is a new exotic pest imported from Asia.  Specimens were first collected and identified in the US in Allentown, PA in 1998 it has spread to 32 states and the District of Columbia and shows no sign of stopping.   This insect causes extensive damage to a wide selection of crops.  It congregates in human structures to overwinter.  There are several native look-alike stink bugs so an expert entomologist is needed to make a positive identification.

Earwig Forficula auricularia is an occasional invader in human habitations.  Earwigs prefer cool, moist, outdoor conditions.  Most species of Earwig have wings folded under the elytra which extend about ¼ the length of their abdomens and are capable of infrequent, clumsy flight.  Their preferred method of escape is to scurry under a nearby object and hide.

Springtail Order: Collembola is a tiny, 1/8” long, gray-colored nuisance pest that occasionally appears in large numbers, usually following cool, rainy weather.  They prefer cool, moist, outdoor conditions and do not thrive indoors.  They feed on decaying organic matter and do not bite.