340 SANITARY ENTOMOLOGY 



breeding on the young. This has been observed in the shaft louse of 

 chickens. On the other hand some of the species, for instance the head 

 louse of chickens, appear to thrive better on the young than on the 

 adults. 



Life Histories. — Very few of the so-called bird lice have been studied 

 fully. Our lack of knowledge of the life histories and habits of these 

 parasites is partly due to the difficulty of successfully rearing them 

 under control. There is a marked difference in the habits of the differ- 

 ent species of lice occurring on the same host. This may be explained by 

 the fact that the parasite has become modified in structure and function 

 of body parts to live under certain restricted conditions. For instance, 

 on the chicken we find the head louse breeding largely on the head of 

 chickens and seldom occurring on other parts. This species hangs to 

 the down on young chickens and is usually found closely adhering to the 

 base of the feathers on the heads of grown fowls. The body louse on the 

 other hand has adapted itself to living on the skin of the host and 

 is not commonly found on the feathers. This species is very active and 

 depends for protection on its agility on the comparatively bare parts of 

 the skin. The shaft louse usually rests along the shaft of the feathers 

 but can run freely on the skin, going from one feather to another. The 

 wing louse is ordinarily found between the barbules on the larger wing 

 and tail feathers, and the fluff louse, a very awkward and sluggish species, 

 clings to the fluffy parts of the feathers, principally on the thighs and 

 sides. 



The eggs of the different lice are laid in the regions where the lice 

 are usually found. The head lice eggs are attached singly to the 

 feathers on the head and neck. The body lice attach their eggs to the 

 base of feathers and are usually found in masses, especially on the base 

 of the feathers below the vent where sometimes the masses become ex- 

 ceedingly large — nearly half an inch in diameter. 



The life histories of a few of the common species have been worked 

 out by Mr. H. P. Wood and the writer. The head louse will serve as an 

 example. The eggs of this species hatch in from four to five days into 

 minute pale rather active larvae and these after molting their skins sev- 

 eral times become adults in from 17 to 20 days, and egg laying begins a 

 few days later. As far as we have observed, the length of the developmen- 

 tal period of the different species is quite similar. 



It is difficult to get any accurate record of the longevity of lice on the 

 host but we believe they live for several weeks if not months. When re- 

 moved from the host the longevity is comparatively short and this of 

 course assists in the application of control measures. The body lice 

 usually die within a few hours, while the head and wing lice are more 

 persistent. Professor Theobald records keeping the shaft louse alive for 



