NOTES ON PEDICULUS VESTIMENTI. 267 



ternal use of drugs may be of practical value though it may have 

 scientific interest. 



As stated above these experiments were suggested by the ap- 

 parent direct response of the louse to the blood of the old sailor 

 who was habitually under the influence of some drug. Further 

 the toxic effect of the guinea pigs' blood and the non-nutrition of 

 the blood of other animals led me to suspect it might be possible 

 to find a drug that given to the host would make his blood dis- 

 tasteful or malnutritions to the lice, causing them to leave their 

 victim, or it might be sufficiently injurious to the reproductive 

 organs to inhibit multiplication. If the sperm or eggs can be in- 

 juriously affected this might prevent fertilization and so control 

 the most effective phase of infestation. The danger from this 

 cause is obvious from the fact that a single female lays about ten 

 eggs a day 1 and as soon as these hatch (in five or more days) the 

 nymphs begin to bite at once feed during the day and night, 

 and when mature (after about 20 days) the new life cycle 

 begins. Thus the danger from a single fertilized female is ap- 

 parent. 



The mature insects, which are about 3 mm. long, can be easily 

 found and as they are by no means active they can be readily 

 caught and killed. The eggs and nymphs, however, cannot be so 

 easily eliminated, for they are so tiny they may escape detection. 

 It is obvious therefore that any effort made to inhibit or even 

 limit reproduction is justified and worthy of patient experiment. 



The first difficulty encountered was to find a host who would 

 be willing not only to feed the lice but to consent to being drugged 

 daily for at least a month as that was the period selected in order 

 to determine any possible effect not only on the rate of repro- 

 duction but on the life of the nymphs as they may possibly be 

 more susceptible to the food supply than are the adults. After 

 finding a suitable host the experiments were conducted in the 

 laboratory on a limited number of pairs of P. vestimenti and in 

 order to detect any deviation from the normal a daily record was 



1 Nuttall, '17, page 130 "We may therefore conclude that under optimum 

 natural conditions 275 or 300 eggs represent the normal number of eggs which 

 a female is capable of laying and that during the greater part of her oviposi- 

 tion period she days 9 to 12 eggs a day or an average of 9.7." 



