SIPHON APTERA 327 



The mouth-parts are formed for piercing and sucking. When seen 

 without dissection, the following parts are apparent; the maxillae, which 

 are triangular plates; the maxillary palpi, which are long and four- 

 jointed; and the proboscis (Fig. 570). 



The eggs of fleas are scattered about the floors of dwellings and 

 in the sleeping-places of infested animals. The larvae are slender, worm- 

 like creatures, with a distinct head and without legs. (Fig. 569.) They 

 have biting mouth-parts, and feed upon the decaying particles of animal 

 and vegetable matter always to be found in the dirt in which they live. 

 When full-grown the larva spins a cocoon within which the pupa state is 

 passed. 



Fleas are parasitic only in the adult state. Some species infest birds, 

 but by far the larger number prey upon mammals, and most mammals 

 are subject to the attacks of these parasites. Although the different 

 species of fleas infest different hosts they are not so restricted in their 

 host relations as are many parasites, and may pass from their normal 

 host to another species; for example, both the dog-flea and the cat-flea 

 frequently attack man. 



Formerly fleas were regarded as merely annoying pests of man and his 

 pets; but it has been found that fleas are the carriers of bubonic plague; 

 this fact has greatly increased the interest in these insects. 



Except where bubonic plague is present the bites of fleas are not likely 

 to cause serious results, although they may be very annoying. The irri- 

 tation caused by them can be relieved by the use of some cooling applica- 

 tion as menthol, camphor, or carbolated vaseline. Scratching the bites 

 should be avoided as that aggravates the inflammation. 



There are hundreds of species of fleas in the world but the following 

 forms are among those best known because they are most intimately 

 associated with man: 



The cat-flea, Ctenocephalns Jelis. — This is the species that is most 

 often found in our dwellings in the East and in the South, and the one 

 that most often attacks man in these regions. This species infests dogs 

 as well as cats. Its head and thorax bear rows of short, stout, dark 

 spines known as ctenidia. 



The dog-flea, Ctcnocephalus cams. — This species is closely allied to 

 the cat-flea. It infests dog, cat, and man. The head and thorax bear 

 ctenidia. 



The human flea, Pulex irritans. ■ — On the Pacific Coast this is the 

 species that is most often found in houses attacking man. It is easily 

 distinguished from the two preceding species by the fact that its head and 

 thorax lack ctenidia. Man is its natural host; but it will infest various 

 other animals temporarily. 



The Indian rat-flea, Xenopsylla cheopis. — Among the various species 

 that are supposed to transmit the bubonic plague, this cosmopolitan 

 species is regarded as one of the more important. It resembles the human 

 flea in lacking ctenidia. 



The sticktight flea, Echidnophaga gallinacea. — This is a very serious 

 pest of poultry especially in the southern and southwestern portions of 

 the United States. It is a small, dark brown species, which is often found 

 in dense masses attached to its host; heads of chickens are often covered 

 with dark patches of these fleas. While this species is chiefly a pest of 

 poultry, it is often found in dense masses on the ears of dogs and cats. 



