Flea Facts, Identification and Control
Scientific Order: Siphonaptera
Common family: Pulicidae
Cat flea (Ctenocephalides felis)
Dog flea (Ctenocephalides canis)
Human flea (Pulex irritans)
Oriental rat flea (Xenopsylla cheopis)
Size: Very small; 1/12 to 1/4 inches (2.12 to 6.35 millimeters)
Color: Can include dark brown, black, brown-black, gray, or dark red-brown. Often semi-translucent
Behavior and Diet
Fleas are parasitic insects that feed on mammals, including humans and pets. Most species of flea prefer to feed on a specific type of host. Fleas derive their common names from their preferred hosts; cat fleas prefer to feed on cats, dog fleas on dogs, and so forth. However, fleas aren’t too picky to feed on other hosts when their preferred meal isn’t readily available. All common flea species can feed on humans.
Fleas require a blood meal for nutrition and the energy required to reproduce. They acquire their blood meals by latching onto prey and using specialized, piercing-sucking mouthparts to draw and consume blood. While feeding, fleas secrete a skin-irritating saliva from their mouthparts. Flea saliva may cause itching, skin lesions, welting, or rashes. Sensitivity to flea saliva varies from host-to-host. Some fleas may also transmit diseases from animals to humans through saliva-blood contact between multiple hosts. The oriental rat flea Xenopsylla cheopis was infamously responsible for the proliferation of the bubonic plague when it fed on rats and then humans.
Unlike ticks or most other pest parasites, fleas do not permanently stay latched onto their prey, and may jump on and off of a host repeatedly. Fleas usually detach from hosts when they’re gorged with blood to either mate and reproduce or rest and digest in dark, humid hiding places. They generally remain in these hiding places until they need to feed again.
Fleas are wingless and cannot fly. Instead, fleas developed long, powerful hind legs that are well-adapted to leaping. Fleas use these legs to leap up to 13 inches. They attack hosts by leaping from either the ground or an elevated position directly onto the host and then climbing to a bite-vulnerable area of the body. Fleas commonly leap onto pets outside and may become a problem after entering the home while concealed on the pet. Usually, fleas bite human ankles when attempting to feed on them.
Reproduction and Life Cycle
Mature female fleas usually lay eggs directly on a host they are actively feeding on. These eggs aren’t attached to the host, however, and generally fall off and continue to incubate on the ground or in the host’s home. If your pet has fleas, for instance, it’s probable that there are flea eggs in its bedding.
Fleas lay eggs after each blood meal. The number of eggs laid depends on the species of flea; some fleas lay only 4 to 8 eggs per meal, while other species, like the cat flea, may lay up to 25. Most fleas lay several hundred eggs in their lifetimes.
A flea’s life cycle is broken into four distinct developmental stages: egg, larva, pupa, and adult.
Flea eggs are white, oval-shaped, tiny (about 1/50 of an inch--less than one millimeter!), and difficult to see with the naked eye. The length of the egg incubation period depends on environmental factors like the temperature of the incubation site.
In an ideal environment, with 65 to 80 degree F temperature and high humidity, flea eggs could hatch in as few as 2 to 12 days. In less-than-ideal conditions, the eggs may take up to 20 days to hatch.
When fleas first hatch they are larvae. Flea larvae don’t look anything like fully-developed fleas, resembling small worms instead. They’re ¼-inch long with thin, translucent white bodies covered in tiny, bristly hair. Their heads are prominent and dark brown.
Larvae remain near their hatching site and feed on their own molting skin or on the feces of adult fleas. They molt three times, growing in size after each molt. The amount of time a flea spends as a larva varies based on environmental factors. This phase could last anywhere from a week to 200 days. After the third and final molt, the larvae spins a silk cocoon for itself and begins pupation.
During the pupal stage, the flea remains in a resting stage within the cocoon as it metamorphosizes into a fully developed adult. The pupal stage generally only lasts 5 to 14 days, but adult fleas tend to remain in the pupal stage until they’re stimulated by vibrations on the surface of the area where their cocoon rests, the presence of a desirable host, or the proper environmental conditions. Fully formed fleas may remain in the resting pupal stage for months before emerging.
Adult fleas emerge from their cocoons fully formed and ready to begin feeding immediately. They will often attack the first possible host they encounter to gain nutrients quickly. Fleas can survive for several days without a blood meal, but they prefer to feed multiple times a day.
Fleas generally target the most accessible host of their preferred kind first, so often a single flea will feed on a host several different times. Adult fleas are surprisingly long-lived; the common cat flea has been known to live and feed for over a year.
Signs of Infestation
If you have a pet, make note of how often they scratch themselves, especially in vulnerable areas like behind the ears. If your pet seems to scratch a lot, search it for fleas by gently pulling the fur away from its body and feeling the skin for bumps or bites. Flea bite scabs are small, black- or rust-colored spots that may be inflamed or puffy. Comb your pet with a flea comb frequently and inspect it after each brushing session.
Look for flea eggs in your pet’s house or bedding. Flea eggs look like tiny, grainy or sandy grey or black buildup. It may resemble dust or salt and pepper.
Check yourself for small, itchy flea bites, particularly around the shins, neck, or ears. Examine your body thoroughly when bathing. Fleas bites resemble smaller mosquito bites and may be darker in color. Flea bites don’t usually swell, but they may itch or turn red. Fleas often bite a host more than once, so look for patterns of 2 to 3 bite marks in close proximity.
If you notice other flea symptoms, make note of how often your pet goes outside, where it goes when it’s outside, whether or not it comes into contact with other animals, and how long it stays outside. Examine your pet thoroughly when it gets back inside. Flea infestation becomes more likely the more time your pet spends time outdoors, especially if they interact with other animals.
Treatment and Prevention
Wear long socks tucked into long pants when you’re mowing the lawn or out walking. Thoroughly wash and dry your clothing whenever it becomes dirty. Check yourself for flea bites whenever you get inside, especially from humid or forested areas.
Invest in an anti-flea collar or treatment for your pet, especially if they spend time outside. Check them for fleas immediately when they come inside and comb them with a flea brush regularly. Thoroughly wash and clean your pet’s living area frequently, especially their bedding. Consider throwing out and replacing your pet’s bedding if you discover it has fleas.
Vacuum thoroughly and frequently. Consider having your carpets shampooed and/or steam cleaned to remove any larvae or eggs that may be hiding in them. Dust surfaces frequently, especially in dark areas of the home that aren’t often accessed, such as a basement or cellar. Practice humidity control and consider investing in a dehumidifier for vulnerable areas. Mop hard floors frequently, and make sure to dry them thoroughly when you’re finished.
Keep your lawn mowed short and trim hedges, bushes, and ornamental plants frequently. Try to keep wild animals or other pets from accessing your yard if possible. Do not allow lawn debris or garbage to accumulate in piles nearby. Keep your dumpster at least 10 feet away from the threshold of your building.
New York City Department of Health and Mental Hygiene’s Flea page
Ohio State University College of Food, Agricultural, and Environmental Science’s Fleas fact sheet
University of Florida IFAS Extension Fleas page
Bugguide.net’s Fleas page
Cornell University Department of Entomology’s Flea Insect Diagnostic Laboratory fact sheet
Michigan State University Pesticide Safety Education Program’s Flea fact sheet
Washington County Health Department’s Fleas fact sheet
Penn State College of Agricultural Sciences Department of Entomology’s Cat Fleas Insect Advice Extension page