PARASITES OP ANIMALS. 



13 



tunities offer it is always ready to jump upon the naked feet 

 or ankles, and may thus gain entrance to the bed. Many 

 persons, especially ladies and children, are badly poisoned by 



Figure 17. Figure 18. 



them, and may suffer severely for several days from the bite 

 of a single flea; for, unlike the mosquito and other blood- 

 sucking insects, they are never satisfied with a single bite, or 

 with one spot, but must travel about and bite as they go, 

 literally " biting on the run." In these respects, however, it 

 agrees closely with the so-called human flea (Pulex irritans). 



The cat-flea (Figure 17) is dark chestnut-brown in color, 

 and is stouter and thicker in the thoracic region than Pulex 

 irritans, which has a rather slender waist and darker color. 

 There is a row of sharp spines along the lower side of the 

 head on each side, and another row of similar spines on the 

 posterior edge of the first segment of the thorax; but the 

 human flea lacks both these sets of spines. Other good dis- 

 tinctions are found in the joints of the feet or tarsi, and in 

 the mouth organs. In all fleas the males and females differ 

 considerably in form and size, the males being smaller and 

 shorter. 



The female cat-flea lays her eggs among the fur of the cat, 

 to which they are but slightly attached ; these eggs are very 

 small, white, and long-oval. As the cat walks or runs about, 

 the eggs are constantly being scattered around, often in great 

 numbers. On one occasion I was able to collect fully a tea- 

 spoonful of these eggs from the dress of a lady in whose lap a 

 half-grown kitten had been held for a short time. The places 



