LICE WHICH AFFECT DOMESTIC ANIMALS 333 



ously mentioned species, they move about considerably among the hairs, 

 having feet well adapted for this purpose. 



These lice are small, yet visible with the naked eye, measuring about 

 one-thirteenth of an inch. They are reddish in color, having distinct 

 bands across the abdomen. The general shape of the body is quite dif- 

 ferent from that of the sucking lice, for their heads are broad and blunt, 

 while those of the sucking lice are much more pointed. 



The problem of working out the life history of these lice was much 

 more difficult, and the length of time during the various stages could 

 not be worked out with the degree of accuracy that was possible with 

 the less active sucking species. 



The eggs hatch in from five to seven days. The period from hatching 

 until the lice are mature and eggs are laid again, is about fourteen days. 

 The eggs are delicate white, flask-shaped forms, having a small cap or 

 lid on one end that is removed when the egg hatches, while the other end 

 is firmly glued to the hair. 



It was found more difficult to exterminate these small red lice either 

 with sprays, oils or fumigations than it was to kill the larger sucking 

 lice. This was possibly due to their more resistant chitinous covering, 

 their large numbers and their activity. 



METHODS OF STUDY OF LIFE HISTORIES 



Much time was taken to determine the periods of incubation of the 

 eggs of different species of the cattle lice and the length of time necessary 

 for the lice to mature, because this was considered an important feature 

 that would determine the proper length of time between applications of 

 control measures. It would be difficult to find any substance active 

 enough to kill the embryo louse in the egg, thus preventing it from 

 hatching, and at the same time not be so active as to do injury to the 

 skin of the cow. The control must therefore be based on some other phase 

 of the life cycle. 



In order to make sure of no previous infestation, the method was to 

 isolate a new-bom calf and place adult female lice that had been fer- 

 tilized upon the shoulders of the calf and watch for the first presence of 

 eggs. As a rule these were found a few days after the lice were placed 

 on the calf. Eggs were examined each day and as many of the old lice 

 as could be found were removed from the animal. It was surprising 

 how many of the sucking lice could be found after they had been placed 

 on the shoulders of the calf, for they moved but little from where they 

 were first placed. The calf was thrown on a bundle of hay each day at 

 the same hour and the caps on the eggs were watched. Where these were 

 found removed, the period of incubation was recorded. 



