254 
Bionomics of Pediculus 
With the F. 1 generation of reverse cross, P. humanus c? and P. capitis 
the disparity was not so obvious. 
The first trial failed owing to the death of the ? whilst pairing. 
A second attempt was more successful and about 50 eggs were laid, 
the $ dying on the 17th day. 
The F. 1 generation consisted of 27 dd (= 55 %) and 22 $$ (== 45 %). 
In the third trial the $ died after laying one egg. 
A fourth attempt was made; two $$ of P. capitis being confined 
with one d of P. humanus. One of the died within a day or two and 
the other was left with the she laid about 30 eggs, but died within 
10 or 12 days. 
The F. 1 generation from this pairing consisted of 17 (= 71 %) 
and 7 ?? (= 29 %). 
One or two other attempts were made which resulted in the death 
of the ?$. 
Of the subsequent generations reared from the F. 1 generation of 
the second pairing, a large number of specimens were reared and killed 
as they reached maturity. They consist of a portion, not the whole, 
of the offspring of two single pairings and a number of pairs left together 
in a stock box. 
The specimens of the F. 2 generation are 
143 SS (= 57 %), 109 ?? (= 43 %) and 6 nymphs. 
The specimens present of the F. 3 generation are 
63c?cJ (= 50%), 64 ?? (=50%). 
In size the specimens of the F. 1 and F. 2 generations of both crosses 
are generally intermediate between those of P. humanus and P. capitis, 
but in the F. 3 generation considerable disparity was noticeable—some 
very large dd and some very small being observed. 
In the F. 2 generation, observations were made in regarjjl to the egg 
laying habit, both hair (human) and cloth having been placed in boxes 
with a few selected pairs of hybrids of the F. 2 generation of the cross 
P. capitis d and P. humanus $. I noticed that the laid on hair for 
choice, only a few eggs being attached to the cloth, but the lice showed 
the instinct to cluster their eggs, a few only being generally scattered 
along the hairs as is the case with eggs of P. capitis^. 
^ The F. 1 generation of this cross, resulting from a later pairing, show a marked 
preference for laying on cloth; out of four pairings three $$ laid their eggs on cloth, 
while one selected hair and laid nearly all her eggs upon it. Unfortunately I was too 
busy to note the egg laying habit of the F. 1 generation of the earlier pairing. 
