EXTERNAL PARASITES 237 



louse of chicks, while the latter, smaller in size, is commonly 

 foxmd on the bodies of the adult birds. 



There is still another variety of lice which may infest chick- 

 ens, but these two are by far the more common. 



On turkeys there may be found two kinds. The more com- 

 mon variety is scientifically known as the Gonoides styhfer. 



Ducks and geese each come in for their distinct varieties, 

 and on the pigeon the Lipeurus baculus is the long slender 

 louse, with long narrow head, thorax, and abdomen, so com- 

 monly seen in the pigeon cotes. 



Description. — The female louse is a trifle larger than the 

 male. Lice multiply or propagate by laying eggs, often called 

 nits, which are oval in shape and white in color, and are ce- 

 mented to barbs of the feathers by the female with a small 

 amount of cement with which she is provided. In a few days, 

 usually ten days to two weeks, depending on the temperature 

 and other conditions, the young louse escapes from the egg 

 by raising a small cap or piece of the egg covering. The j'oung 

 are lighter in color than the adults, but have about the same 

 shape and appearance otherwise. The females are usually 

 more numerous than the males. The lice now grow to full 

 development and, under favorable conditions, may live for 

 several months. During their growth to maturity they molt 

 several times, each time taking on a slightly darker tinge. 



Lice multiply very rapidly in hot weather, at which time 

 they find conditions for existence most favorable. One pair 

 of lice under the most favorable conditions may possibly be 

 grandparents to over 100,000 descendants in the short space 

 of two months. 



Chicks hatched in the incubator are free from lice, and stay 

 so until placed with lousy hens or in lousy brooders or other 

 surroundings. 



Lice hve for a considerable time off the hosts (birds). 



Symptoms. — ^Lice produce irritation, and large numbers 

 seriously interfere with the health, growth, and development, 

 as well as egg production and fattening processes. 



A lousy bird is noted to scratch and pick at its feathers. It 

 shows signs of being drowsy, may refuse to eat, and in growing 

 birds the body development or growth is interfered with. 



