Forest Preserve District of Cook County, Illinois
Nature Bulletins
Newton Home Page

Introduction and Instructions

Search Engine

Table of Contents



Nature Bulletin No. 293-A   February 10, 1968
Forest Preserve District of Cook County
Richard B. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation

Did you ever have fleas? We hope not. Just one of these tiny tormentors can cause a lot of commotion because it bites again and again, usually 2 or 3 places in a row, especially about the legs or waist. The bites itch more and more, for several days. The flea is hard to find and harder to catch. A stray cat or dog, sleeping under your porch, may leave enough fleas and flea eggs to start an epidemic; or your own pet may get them from other animals. The Dog Flea and the Cat Flea both feed on dogs, cats or people.

Fleas rank next to the bees, wasps and ants at the top of the insect world, and are the only group of wingless insects which have four life stages (complete metamorphosis): egg, larva, pupa and adult. The adult has a flat hard-skinned body, very thin from side to side, which permits it to slip between the hairs of feathers of the animal on which it feeds. Its mouth parts are made for piercing the skin and sucking the blood of its host. The large hind legs enable it to jump as much as 13 inches horizontally and almost 8 inches high.

A female may lay several hundred eggs, a few at a time, on the animal or in its bedding and the dirt around it. The eggs are not glued in place, as is the case with lice, and usually fall off. The hairy thread-like larva, without legs or eyes, has chewing mouth parts and feeds on animal matter or filth. When full grown it forms a cocoon of white silk -- the pupa stage. The length of time spent in each stage depends upon the species, the weather and other conditions, so that 2 weeks or as much as 2 years may elapse from the time an egg is laid until the adult emerges, ready to leap upon anything that passes by. Further, an unfed adult may remain alive a year or more. This explains the fact that one time, when our family returned home after being absent several months, we found the house alive with leaping hungry fleas.

There are at least 500 species of fleas and almost half of these are found in North America and the West Indies. All of them feed on warm- blooded animals; usually on a few kinds of wild mammals or birds. Only a few species affect man but these are very troublesome -- even dangerous -- because they may shift from one host to another and some of them transmit diseases. The Human Flea, common in the West Indies, occurs in some of our western states where it is found on hogs, dogs, skunks, rats, mice, or deer as often as on man and in his dwellings. The fur-bearers and all kinds of rodents have fleas.

In the great outbreaks of bubonic plague, fleas have been the most important factor in the spread of this terrible disease which is fatal to rats, monkeys and man. At least 9 species may carry it but the worst is the Indian Rat Flea now found in many places in this country. The California Ground Squirrel Flea, which also bites rats, spread bubonic plague among the ground squirrels in several Pacific and mountain states. Rodent fleas also transmit tapeworms, typhus fever, and probably tularemia or rabbit fever.

The Sticktight Flea, which frequently kills young poultry and causes hens to quit laying eggs, also attacks dogs, cats, horses and man. This flea imbeds its whole head in the skin. The Chigoe Flea of the West Indies feeds on blood and then the female burrows into the skin of some animal, frequently between the toes and under toenails of people. As the eggs develop, her body may become as large as a pea and cause a serious ulcer.

David Harum said: "a reasonable amount o' fleas is good fer a dog -- keeps him from broodin' over bein' a dog, mebbe".

To return to the Nature Bulletins Click Here!
Hosted by NEWTON

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Sponsered by Argonne National Labs