304 SANITARY ENTOMOLOGY 



stereotyped account of the life history, on the assumption that this article 

 will be read by all those interested. 



The first point to be noted is the fact that body lice may occur on 

 the body as well as on the clothing. Nuttall has brought out convincing 

 evidence that nits as well as lice themselves are often found upon the body 

 hairs, especially in the axillae, the hairs of the breast, and at times on tlie 

 pubic hairs and even the hairs of the thigh and leg. We have seen two 

 cases in which both lice and nits were present in the axillae. The impor- 

 tance of this point as regards control measures is obvious. Disinfection 

 of the clothing is not sufficient, but must be accompanied by a thorough 

 bath with some insecticidal liquid, such as cresol-soap, or the kerosene 

 soap used by Boyd in his work with the Mexican laborers of the Sante Fe 

 Railroad. 



Moreover, it was soon discovered from actual experience in this war 

 that a disinfection of a part of the clothing was entirely ineffective ; for 

 example, if clean shirts are provided, while the trousers have not been 

 cleaned, lice quickly migrate from the trousers to the clean shirt which 

 affords them new areas for deposition. Thus conditions are soon as bad 

 as before. 



A second point having an important bearing on control measures 

 is the number of eggs laid per female and their rate of development. The 

 importance of the improved technique for rearing lice, mentioned above, 

 consists in showing that previous statements, regarding the number of 

 eggs laid, clearly underestimated their power of reproduction. When the 

 licei are fed but twice a day only four to five or six eggs arc obtained per 

 day, while by the wristlet method Nuttall obtained as high as twelve eggs 

 per day per female, the average being about ten. He states that cor- 

 poris may lay 275 to 300 eggs during its lifetime. By the same method 

 the senior writer has obtained as high as fourteen eggs per da}^ with an 

 average of about eleven per day over a period of twenty-five days. 



The eggs are elongate, oboval, with a granulated cap or operculum 

 at the outer end (plate XXII). They are cemented singly to a hair (in 

 all three species), or a thread (P. corporis). Occasionally a single hair 

 will be covered with them. Oviposition usually commences in P. corporis 

 within two days after maturing. 



When a female is ready to oviposit she clings to a hair or thread, 

 and slipping backward, grasps it also with the gonopods and the pos- 

 terior lobes of the last segment. A drop of cement is excreted, followed 

 by the (^gg, which is thus firmly cemented to tlie hair and the insect 

 moves away. The entire operation consumes about 17 seconds. The 

 operculum is usually directed away from the root of the hair. 



Oviposition takes place most readily at about 30° C. (86° F.) and 

 ceases at 20° C. (68° F.). They lay rapidly at 37° C. (99° F.) although 



