HABITS OF BODY LOUSE 393 



According to observations by Sikora, copulation may take 

 place within ten hours after the last moult has been passed, and 

 Bacot also observed cases in which copulation took place on the 

 day of reaching maturity. Egg-laying begins in from one to four 

 days after the final moult and continues at the rate described 

 on the preceding page until the death of the insect. The aver- 

 age length of life for the females is about 35 or 40 days, and 

 probably a little less for the males. 



According to Bacot, hungry lice do not show a tendency to 

 wander on the skin, but proceed to pierce the skin and suck blood 

 at once. Nor do they shift to make another stab, as fleas fre- 

 quently do, if the first stab- does not immediately furnish blood. 

 They apparently place great reliance on the power of the sali- 

 vary secretion, which is poured into the wound, to dilate the 

 capillaries by its irritation and thus cause a flow of blood. Some- 

 times blood is not drawn for several minutes after the puncture 

 is made. Bacot states that lice fill their crops in from two to 

 15 minutes, but Sikora observed that adult lice, if fed only twice 

 daily, sucked for an hour to an hour and a half, and, if left in con- 

 tact with the skin for several hours, have a tendency to pump 

 blood intermittently with short pauses, meanwhile voiding ex- 

 crement containing undigested blood corpuscles. Sikora also 

 observed that hungry lice placed on the well-shaved skin of a 

 puppy made repeated attempts to draw blood without success, 

 and also that dog lice, Hcematopinus ventricosus, tried in vain to 

 draw blcod from the human skin. He concludes therefrom 

 that not only is it necessary for lice to penetrate the skin with 

 their piercing apparatus, but that they must also produce an 

 irritation by means of a salivary secretion, apparently specific 

 in its action for certain kinds of blood, in order to cause blood 

 to flow from the tiny puncture. Apparently the salivary se- 

 cretion deteriorates in unfed lice, for though starved lice may 

 still be able to drive their piercing apparatus into the skin, it 

 takes them three times as long to draw blood. 



A fact of far-reaching significance, if found to be commonly true, 

 has recently been reported by Hall in Texas. This author 

 found that a female body louse taken from a Mexican baby, 

 when placed in a bottle with a head louse taken from the same 

 baby, devoured the head louse. Two head lice were then fed 

 to the body louse daily for three days, and the same louse was 



