Medically Important Arthropods Details

Cat Flea

In Texas, the cat flea is usually the most common species attacking both humans and their pets, causing irritation, loss of blood, and extreme discomfort. In addition, cat fleas are hosts in the life cycles of dog tapeworms which can occasionally infect humans. These fleas are also known to be involved in the transmission of the rickettsial pathogens that cause endemic typhus. A small number of endemic typhus in humans still occurs in Texas, primarily in the southern regions of the state. Treating pets for flea infestations is an important part of controlling these common pests in the household.


Centipedes are fast-moving arthropods having one pair of legs for each body segment. About one hundred and fifty species are known from the U.S., a number of which are found in Texas. Although most are quite small, some species attain a length of greater than 8 inches. Centipedes are predacious and feed primarily on small insects. Many are capable of inflicting venomous bites on humans, but very serious and fatal cases are extremely rare.

Fire Ant

One of several fire ants found in Texas, the red imported fire ant has spread since its introduction in the 1930's to become a common pest in many parts of the state. An aggressive ant, this species will rapidly become defensive to protect its mounds, swarming over the animal or human victim and inflicting both bites and venomous stings. Sometimes the resulting pustules are slow to heal, can become infected, and may leave scars. Recognizing and avoiding fire ants is important, especially for young children that may be slow to respond when attacked. If hypersensitivity, allergic reaction, or infection is suspected, it is advised that medical assistance is obtained promptly.

Kissing Bug

Although they resemble several common garden variety bugs, kissing bugs are strictly blood-feeders and usually nocturnal, hunting blood meals at night or in darkened areas. There are a number of species of kissing bugs, most of which are close to an inch in length. If disturbed or threatened, this bug will quickly inflict a very painful defensive bite. While taking a blood meal, it will feed for about fifteen minutes or until engorged with blood. Such feeding activity is seldom felt by the host and results in a raised, pinkish red reaction. Unfortunately, some of the kissing bugs in Texas are potential vectors of a serious protozoan parasitic infection in humans known as Chagas disease. Very common in parts of Mexico, Central and South America, human cases of Chagas disease are extremely rare in Texas. Please see the DSHS Zoonosis Control Branch for more information


Crab Louse

Crab lice are small grayish-white insects with a short abdomen bearing hairy lateral tufts and large second and third pairs of legs which give them a crab-like appearance. Crab lice are spread, chiefly by sexual contact, but may be acquired by other means such as infested toilet seats and beds, and by close personal contact.

Head Louse

Head lice are small grayish-white insects, 1/16 to 1/8 inch in length. Lice are wingless insects whose legs have claws that are adapted for clinging, giving the louse a strong grip on hair shafts. Head lice live on the head and rarely leave the body for any reason. Lice are usually transmitted through close personal contact. They are less frequently transmitted through the sharing of personal articles.


Scabies Mite

This insidious type of infection is the most important disease condition caused by mites in Texas. Sometimes these tiny arthropods cause only mild infections, but often scabies mites result in serious skin irritations. The immature nymphal stages will live in hair follicles; however, adult mites will burrow under the skin for extended periods of time. Open sores may develop which can be sources for secondary bacterial infections. There have been large outbreaks in Texas (especially in institutions, such as hospitals) separated by relatively quiet periods. Some have named this condition "the seven-year itch."

Tropical Rat Mite

The tropical rat mite is very common on various rodents. Most, if not all, tropical rat mite infestations are traced back to rodent problems. Often, the rodents are trapped or killed but their mite parasites are still present. In seeking a blood meal, they will readily attack humans and domestic pets. Unfed females may live for up to several weeks. However, these mites require feedings on rodents to complete their life cycle. Almost too small for us to see before feeding, tropical rat mites become much more visible after they engorge with blood and take on a reddish appearance. On a case by case basis, specimens for arthropod identification may be submitted to CDC via the DSHS Laboratory. Physicians or other Public Health Agencies should call 512-776-7615 to discuss the need for submission and/or identification.

Suspected mites should be collected in a small vial or bottle with alcohol for identification.

Asian Tiger Mosquito

Since its discovery in Houston, Texas in 1985, the Asian "tiger" mosquito Aedes albopictus has spread to 25 states. This mosquito is a small black species with a single, silver-white stripe down the center of the thorax. Ae. albopictus is a major biting pest and is a competent laboratory vector of at least 22 arboviruses, including many viruses of public health importance. Ae. albopictus is primarily a forest edge species that has adapted to the urban environment. It favors tree holes and artificial containers such as flower pots, bird baths, and discarded rubber tires.


The long slender tip of the scorpion’s abdomen bears a stinger enclosing a poison gland which is used to capture prey and as a defensive weapon. The striped scorpion is common in Texas and does not have a deadly poisonous venom. However, hypersensitivity and allergic reactions may require medical attention. It is not unusual for scorpions to enter houses and hide in closets, attics, garages, and other dark, undisturbed places. Scorpions feed on spiders and other small arthropods.


Black Widow Spider

The black widow spider, Latrodectus mactans, is present all over the U.S. The female is usually jet black and on the underside of the rounded abdomen is a characteristic red or orange hourglass-shaped marking. The black widow spider has a total of eight eyes or two rows of four eyes each and the overall length of the female is approximately 1 ½ inches. The spider is found outdoors in grass, under stones, beneath pieces of wood, in rodent burrows and protected cavities of all kinds. In and around the house it occurs in garages, cellars, rainspouts, and in boxes sheltering water, gas, and electric meters.

The bite feels like a pin prick. In some instances it may not even be felt. Usually, a slight local swelling and two red spots with local redness indicate where the bite occurred. It becomes intense in 1 to 3 hours and may continue up to 48 hours. The symptoms may consist of abdominal pains, rise in blood pressure, nausea, leg cramps, loss of muscle tone and vomiting. When toxin reaches the respiratory centers, there is difficulty in breathing and prostration. If a black widow bite is known or suspected as having been inflicted, a physician should be contacted as soon as possible.

Brown Recluse Spider

This spider has an average adult length of about one half inch, is normally light to dark brown in color, and has short brown hair. The upper head and neck region has a distinct median line which resembles a guitar or violin, which explains its other common name: "fiddle back spider."

The brown recluse has three pairs of eyes whereas most spiders have eight eyes, not necessarily in pairs. This shy, nocturnal spider is found outdoors throughout much of the southwestern U.S. However, indoor infestations often occur and may lead to increased human exposure and bites. In a significant number of cases, local inflammation occurring at the site of the bite may result in a deadening of the skin (necrosis) involving an affected area several inches or more in diameter. In a few cases, systemic disturbances of a general nature have resulted in a rash resembling scarlet fever. Kidney involvement has also been reported in severe cases. If a brown recluse spider bite is suspected, a physician should be contacted as soon as possible. If the spider is killed or captured, the specimen should be submitted to the physician. On a case by case basis, specimens for arthropod identification may be submitted to CDC via the DSHS Laboratory. Physicians or other Public Health Agencies should call 512-776-7615 to discuss the need for submission and/or identification.

Information about testing ticks can be found at the DSHS Zoonosis Control Branch – Zoonotic Health Topics page.

Hard Ticks

The hard tick is distinguished by a dorsal shield. The dorsal shield is small in the female, but in the male it covers the entire dorsal surface. Hard ticks are also tapered anteriorly and the mouthparts are readily visible from the dorsal view.

American Dog Tick

The American dog tick, Dermacentor variabilis, is widely distributed east of the Rocky Mountains and also occurs on the Pacific Coast. The dog is the preferred host of the adult D. variabilis, although it readily feeds on many large mammals including man. The males and females have pale whitish or yellowish markings on the scutum or dorsal shield. Males may be only ⅛ inch long, while engorged females may be as much as ½ inch in length. This tick species is known to transmit Rocky Mountain spotted fever and tularemia.

Black Legged Tick

The black-legged tick, Ixodes scapularis, occurs in the eastern half of the U.S. Common hosts include deer, livestock and dogs. This species readily feeds on humans in the northeastern U.S. and only occasionally in Texas. The males and females are dark brown in color and have no white markings. Males may be only ⅛ inch long, while engorged females may be as much as ½ inch in length. This tick species is known to transmit Lyme disease and babesiosis.

Brown Dog Tick

The brown dog tick, Rhipicephalus sanguineus, is found throughout the U.S. It is a reddish-brown species that attaches to dogs and other mammals, but rarely bites man. This species is one of the most common in homes, where it feeds on dogs and then drops off the infested animal. This tick species can transmit canine ehrlichiosis.

Lone Star Tick

The lone star tick Amblyomma americanum, is found primarily in the southern and south central U.S. It is a reddish-brown species and the common hosts include a wide variety of mammals, including humans, and ground feeding birds. The adult females have a distinct white spot on their back and males have white markings around the outside of their back. This tick species can transmit ehrlichiosis, Lyme disease, Rocky Mountain spotted fever, and tularemia.

Soft Ticks

Soft ticks are leathery and without a dorsal shield. Their mouthparts are subterminally attached and not visible from the dorsal view.

Fowl Tick

The common Argas species found in the U.S. are A. radiatus and sanchezi. These species have been found on various wild birds and it is often called the "blue bug." Ticks of the genus Argas have the margin of the body flattened and show a sutural line, somewhat like the edge of a pie crust. It is parasitic to fowl and is known to transmit fowl spirochetosis.

Relapsing Fever Tick

The relapsing fever tick, Ornithodoros turicata, is found in the southwestern and south central states. This tick has a globular body which appears roughened or warty. Human beings are occasionally bitten by these ticks in mountain cabins, caves, or near wild animal burrows. This tick species transmits tick-borne relapsing fever. 

Last updated May 30, 2013