400 
Biology of Plithiriis pubis 
Duration of the Life-cycle. 
Judging from my two reared females, the life-cycle is completed in 
22-27 days made up as follows: 
Hatching takes 6- 8 days 
Development to adult 15-17 ,, 
Pre-oviposition period 1- 2 ,, 
Life-cycle completed in 22-27 days = Egg to egg period. 
This affords no support to the assertion of Piaget (1880, p. 630) that 
Phthirus “seem to reproduce more rapidly than pediculi,” on the con¬ 
trary, in Pediculus humanus {corporis and capitis) raised by me on the 
body, the cycle was completed in 16-17 days (see p. 161). It is con¬ 
ceivable, however, that the life-cycle of Phthirus may be completed 
somewhat more rapidly on the pubis than on the leg. 
Longevity. 
(o) Unfed, in vitro. 
On dampened pubic hair placed in a corked bottle that was carried 
in the pocket near the body, Marzocchi (1913, p. 314) found that the 
insects mostly died in 10-12 hours. They died more rapidly in open 
vessels exposed to light. Although Galli-Valerio (1913, p. 501) states 
that Phthirus died in two days at 20° C., it appears to me probable that 
they died sooner than he records. 
The following experiments were made by me with adults and large 
larvae that were kept in the dark. 
Lot collected on 
No. of lice 
tested 
Conditions in vitro 
Result 
1. viii. 15, 1 p.m. 
20 
16° C. moist 
3/20 alive after 20 hrs. 
99 
20 
16° C. dry in room 
all dead ,, 20 ,, 
2. viii. 15, 3-4 p.m. 
200 
30° C. moist 
‘’0 
99 99 •• 
a 
99 
hundreds 
20° C. dry in room. 
2 dead after 17 hrs. 
3. viii. 15, 4 p.m. 
many 
danif) weather 
20° C. moist 
20° C. very moist 
20° C. dry 
8 alive after 264 hrs. 
all dead „ 421- ,, 
many feeble in 17 hrs. 
1 moving after 261 ,, 
all dead „ 421- » 
2 dead after 17 hrs. 
1 movmg after 261 hrs. 
all dead ,, 421 ,, 
99 99 ^'^2 99 
