252 
Blo7ioniics of Pediculiis 
occasionally varied by three or four hours. It would be possible for 
the three records of hatching on the 11th day to be due to an earher 
examination than usual on the previous day. 
Table XI gives the record of an experiment of the hatching of batches 
of eggs taken from a stock box and placed under varied conditions. 
None of the eggs_ hatched at room temperature, 15-6° to 18-4° C., but 
a few lice emerged from eggs kept at 24-5° C. 
The widely distributed dates of hatching, in some instances after 
a long interval of time, of these eggs is in marked contrast to the 
uniformly rapid hatching of eggs kept at 36‘1° C. and reminds us of the 
instance recorded by Warburton (1909), although the period of delay 
is far shorter. 
Although the eggs were not counted, there is no doubt that many 
died when maintained at 24‘5° C.; the batch submitted to cool con¬ 
ditions, 15-6° to 18-4° C., was smaller than the one placed at 36'1° C. 
but the number must have been upwards of 100. 
Pediculus capitis. The attempt with this species to parallel the 
series of breeding experiments carried out with P. humanus were less 
successful. Possibly the former constituted a chance observation that 
it would be difficult to repeat without numerous failures, but more 
probably the conditions were less favourable for the head than for 
the body louse. There is, however, probably a real difference in the 
length of life and fecundity of the two insects even if this appears 
somewhat exaggerated in the protocol. 
From Table X it will be seen that four c?d were used in fertilizing 
the series of 20 $?, the first three dying early in their career, but the 
fourth fertihzed 10 $$ and certainly paired once at least with a malformed 
$ that developed no eggs. A shortage in the supply of virgin was 
responsible for the fewer opportunities afforded to this d than to the 
P. humanus. The fact that the in many instances were left longer 
with the $$ than the one day which was usual in the parallel experi¬ 
ment with P. humanus probably accounts for there being no failures in 
fertihzation. Similarly the periods during which the $$ retain the power 
to lay fertile eggs may have been understated since they have been 
reckoned from the date upon which the male was removed. 
Table XIII shows details regarding the hatching of the eggs recorded 
in Table X. Owing to the earlier loss of the power to lay fertile eggs 
in this species, the period is less clearly defined as regards its upper 
limit than in the case of P. humanus, but there is little doubt but that 
it is really shorter by about one-third. 
