394 LICE 



induced to eat crab lice, small black ants, bedbugs, and raw beef. 

 When body lice were placed in a bottle with head lice, bedbugs, 

 and a piece of beef, they ate first the head lice, then the bedbugs 

 then the beef, and finally became cannibals to the extent of the 

 survival of the fittest! This would readily explain such facts 

 as that body lice (according to Hall) can be found in empty box 

 cars used to transport Mexican troops weeks before, and it 

 would account for louse-borne diseases lying dormant in isolated 

 places. A freight car once infected with typhus would be a source 

 of danger for a longer period than the few days a louse can live 

 without food. However, before insectivorousness can be ad- 

 mitted as a usual habit of lice in the absence of normal food, 

 further investigation is necessary. 



Digestion is very rapid. An entire two-hour feed may be 

 digested in from eight to ten hours at 95 F., but digestion is 

 slower at lower temperatures and the stomach contents remain 

 unchanged for ten hours or more at 45 F. or below. At tem- 

 peratures above 95 F. digestion is even more rapid, but there is 

 a high mortality. 



It is evident from Sikora's experiments that 95 F. is the op- 

 timum temperature for the development and reproduction of 

 lice. The absence of lice from hot countries observable in 

 Mexico, for instance, where they are abundant on the central 

 plateau above 5000 to 6000 feet, but absent from the hot coastal 

 strips is apparently not due to the high temperature but 

 probably to the disastrous effect of profuse perspiration and 

 consequent excessive humidity between the clothes and skin. 



The bites of the body louse produce itching red pimples which 

 become covered by a brownish crust, the results of the action 

 of the toxic salivary juices. Scratching produces characteristic 

 white scars, surrounded by brownish pigment; in fact, large 

 areas of the skin may take on a mottled bronze color. The color- 

 ing of the skin is said to be due to the stimulation of pigment 

 formation in the skin by toxins secreted by the louse. Many 

 individuals develop an insensibility to the bites of lice, a fact 

 which probably explains the indifference of some communities 

 to them as, for instance, the people of Russian Poland. 



Head Louse. The head louse, P. humanus capitis, is very 

 closely related to the body louse, and is, in fact, thought by some 

 workers to be a mere variety of the latter. Aside from its different 



