210 Bioloyy of Pediculus human uh 
the other (6) being left white, whilst instead of a hair-grid, a narrow strip of 
cloth was wound inside against the sides of the box. The white box contained 
white flannel, the black box contained black cloth, and its gauze top was 
blackened. The lice were fed twice daily on my Laboratory Assistant’s arm, 
and, between feeds, were maintained at 31° C. in a glass-doored thermostat 
t _ 
facing a window. But little light penetrated the boxes through their upturned 
gauze fenestra and the insects were disturbed as little as possible. The adults 
began to emerge in both boxes on the same day (5. vi. 18), and 77 out of 92 
reached maturity, the black box containing 40 (18 d, 22 $) and the white box 
37 (16 <$, 21 $). The results in respect to pigmentation were as follows: 
(a) Black box', all the adults (40) were very darkly pigmented, almost as 
dark as specimens of capitis collected from African negroes. The whole 
integument appeared ashy, whilst the heavily chitinized structures (sides of 
thorax, pleurae, plates, dorsal bands of male, etc.) were blackish brown and the 
head and legs dark. (See Plate X, fig. 1.) 
( b) White box : all the adults (37) were pale, whitish or translucent, a few 
females showed moderately pigmented genital plates, sides of thorax and 
heads, but almost all had colourless pleurae and legs. (See Plate X, fig. 2.) 
The eggs laid by the lice in boxes (a) and (b) were left in situ, hatched out 
at 31° C., and the larvae raised to adults without being disturbed (see Expt. 
III). The black adults from box (a) were transferred on 11. vi. 18 to white 
boxes and the pale adults (6) to black boxes (see Expt. IY). 
Experiment II (Black, white, gray). 
The same parent lice that were used in Expt. I, to the number of 2 dd 1 and 
4 were allowed to lay six batches of eggs in as many pill-boxes. Three 
boxes were placed fenestrum up in the thermostat whilst three stood bottom 
up with the gauze resting on the floor of the thermostat or on black cloth to 
exclude the light. 
A. Boxes with gauze fenestra uppermost. 
(c) Black box , contained 30 eggs laid 22-23. v. 18. Hatching began 29. v. 
and 16 adults emerged 8-11. vi. Examined 6-8 days after moulting, 15 
appeared dusky and darkly pigmented, and 1 $ was moderately dark. 
( d) White box, contained 31 eggs laid 23-24. v. 18. Hatching began 30. v. 
and 19 adults emerged 9-11. vi. Examined 6-8 days after moulting, 17 
insects appeared pale and 2 females showed slight pigmentation at the sides 
of the thorax and pleurae. 
(e) Gray box, contained 27 eggs laid 24-25. v. 18. Hatching began 31. v. 
and 19 adults emerged 12-16. vi. Examined 6-10 days after moulting, the 
colouration of each individual being separately noted with reference to a 
colour scale, the insects showed various grades of pigmentation. A few' w r ere 
very slightly pigmented, the majority moderately pigmented, but none v r ere 
as dark as those in black box (c). 
