A. Bacot 
•257 
The fertility of the eggs laid was not affected by increased feeding. 
The greatest number of fertihzed eggs laid by a $ P. humanm after the 
removal of the ^ was 115 (? No. 9), with a $ showing a higher daily laying 
average this might well be exceeded. With P. capitis the parallel figure 
is 70 (? No. 9). The of both species, after arriving at maturity, 
started oviposition irrespective of their having paired or not, but eggs 
laid by virgin ?? were invariably infertile.* 
Length of life. The fife of the ^ P- humanus used in the experiment 
recorded in Table I was 32 days; the longest $ life was 46 days, with 
an average of 34. For P. capitis the figures were; d fife 30 days; 
$ fife 38 days, with an average of 27 days. Whether or not the average 
lives of the insects would be extended by unrestricted feeding is an 
open question. 
The fife of the hybrid insects was not noticeably shorter than that 
usual for P. humanus, and they seemed to thrive better than P. capitis. 
Tests made with unfed P. humanus showed that the longest fives 
were at a medium temperature of 16° to 18° C., many of the insects 
living from three to four days, while two lived five and one lived seven 
days. At 24-5° C. all died within five days. At 361° C. all died within 
three days. 
Newly-hatched larvae, unless fed, lived less than 24 hours at 36’1° C., 
and when kept in a box in the vest pocket they lived but little more 
than a day; none survived a second day. 
Adults kept.in a box in the side pocket of a coat lived five days 
without food; this was in March. 
Moulting. 40 young Jice were reared in a box carried in a vest 
pocket and particulars of their moulting recorded. 
1st moult: 3 % moulted on the 3rd day; 42 % on the 4th and 
55 % on the 5th day. 
2nd moult: 15 yo nioulted on the 7th day; 72 % on the 8th and 
13 % on the 9th day. 
3rd moult: 5 % moulted on the 10th day; 3 % on the 11th, 55 % 
on the 12th, 32 % on the 13th day, while 5 % took 14 days to reach 
maturity. 
The (Jd usually mature rather earlier than the 
Cold. Active specimens of P. humanus survived two days at a 
temperature of — 2*3° C. to — 1*1° C., but none recovered after exposure 
to these conditions for a week. 
Hatching of eggs. Table IX shows that vmder humid conditions 
at 31° C. 3 % of the 1300 eggs tested hatched on the 7th day; 56 % on 
