Fleas

Introduction

Fleas are troublesome ectoparasites on mammals and birds. They infest homes, bird cages, poultry houses, offices and other structures housing animals. Both males and females bite and suck blood; the bite often leaves an itchy red spot. Some kinds of Fleas transmit diseases such as bubonic plague, endemic typhus and tularemia to man. This is because many Fleas feed on a variety of animals or birds, and are able to spread diseases from one kind of animal to another; also, the Cat Flea and the Dog Flea are intermediate hosts for the dog tapeworm, which may infest man.

Effects of Flea Bites

Some people are more susceptible than others to Flea bites; some people become immune to any reaction after being bitten often over a long period. A typical Flea bite has a small, central red spot surrounded by a red halo and a little swelling. Bleeding usually occurs.

Description

Several species of Fleas attack mammals and birds. The Dog Flea (Ctenocephalides canis) and the Cat Flea (C. felis), which look very much alike, are the most widespread and the most troublesome as household pests. Both species attack dogs and cats and, sometimes, man; especially if the family pets are away. In general, Fleas stay off their hosts much of the time, attacking them only to suck blood.

Other species occasionally attack humans. The European Chicken Flea (ceratophyllus gallinae) is fairly common on poultry and in birds' nests. When the nests are built on buildings, this Flea often becomes a pest indoors, particularly after the young birds have left the nests. The western chicken Flea (C. niger) occurs on domestic and wild birds. The Human Flea (Pulex irritans) thrives as well on pigs, dogs, cats, goats, rats and many wild animals as on man, and is a serious pest in the Mississippi valley and the Southwest. Its bite is painful, and it may bite several times within a short period.

The Oriental Rat Flea (Xenopsylla cheopis) is fairly numerous as well as the European or Northern Rat Flea (Nosopsyllus fasciatus). These species are principally pests of rats and other animals including ground squirrels, field mice, chipmunks and rabbits, but may also bite man.

Adult Fleas are small, wingless insects with hard, dark-colored bodies; because their sides are flattened, like a goldfish, and each segment has one or more rows of backward-pointing spines or bristles, the insects can move easily among the hairs or feathers of the hosts.

Life History

The four stages of development of Fleas are: egg, larva, pupa and adult. The time for completion of the life cycle from egg to egg varies with species, temperature, humidity and food. Under optimum conditions a generation can be completed in as little as two weeks. However, it can be as long as eight months. The female Flea does not lay eggs until she has sucked blood.

The female usually lays her eggs, which are smooth, oval and light-colored, loosely among the hairs or feathers of the host. The eggs drop off and in a few days hatch into tiny, wormlike larvae. In homes, they develop in crevices in flooring and along baseboards, under the edges of rugs, and between cushions in upholstered furniture. They feed on organic material such as the faeces of adult Fleas, and on bits of dead skin, feathers and hair. The three larval instars are completed in from one week to several months after which they spin tiny cocoons, usually covered with debris, and change to pupae. After about a week or longer, the adults emerge from the cocoons. Under unfavorable conditions they sometimes need several months to develop from eggs to adults. Most of the Fleas found in North America overwinter in one of the immature stages, and the adults become abundant during summer and fall.

Flea larvae need moisture, thus Fleas are often numerous in sandy regions, because sand holds moisture more uniformly than most soils. The sawdust in woodyards is also a good breeding place. Although the expression "sand Fleas" is not uncommon, successive generations of Fleas cannot develop in sand areas unless they feed on animals, since the food of adult Fleas is blood. Fleas may feed several times a day when hosts are near, but adults can live for several months without food. Humans are attacked most by Fleas which cannot find their usual hosts. Dog and Cat Fleas in homes become starved when pets are kept outside during warm weather or are boarded out during vacations. Often upon return from vacation, homes are overrun with Fleas that have hatched while the occupants were away. Flea infestations may last for weeks or months after pets are removed, unless spraying properly controls them.