186 
NOTES ON HEAD- AND BODY-LICE AND UPON 
TEMPERATURE REACTIONS OF LICE 
AND MOSQUITOES. 
By F. M. HOWLETT. 
I. On Head- and Body-Lice. 
The examination of a - large number of individual lice in India, 
where the facilities for obtaining material are unusually good, has 
impressed me with the fact that the characters ordinarily given as 
differentiating corporis from capitis are all to a greater or less extent 
inconstant and unreliable. In general, however, capitis is more 
heavily chitinized and the chitin is of a darker colour with less smooth 
outlines. The size is very variable, but corporis has an easier life and 
is more often large. 
My assistant Mr Patel and I have both reared capitis on the body, 
to ascertain whether the changed conditions would affect these charac¬ 
ters in any way. Our experiments were carried out in 1912 and 1913 
at the Pusa Research Institute, and gave practically identical results. 
The lice when put on the body showed a distinct tendency to migrate 
to the head, and had to be put back again- at intervals, but this character 
was markedly modified in their offspring, some of whom showed no 
definite tendency headwards. The eggs of these (F. 1) individuals 
were mostly laid on clothing; a few (in my case) on the hairs of the 
body, but fewer than those on the clothing. In the next (F. 2) 
generation the migratory tendency had very largely disappeared, and 
though a few individuals still shoved it to some extent it was much less 
definite than in their grandparents. The majority did not show it at all. 
Chitinization and colour were also greatly modified in the corporis 
direction. I can best express the extent to which this modification 
had gone by saying that I am convinced that if these F. 2 adults had 
been sent without explanation to an expert for identification, more than 
75 % of them would have been pronounced to be corporis, and the 
remainder would nearly all have run an excellent chance of being put 
into the same category as slightly aberrant forms. The total number 
of F. 2 lice was in my case something over 40. When the experiment 
