G. H. F. Nuttall 
205 
indigo and blue gave the next highest figures. In Set I the numbers fell 
steadily from violet down to red, in Set III the fall was less regular. In Set II, 
whilst the lice showed a preference for violet and indigo, they behaved 
irregularly toward the other colours, this being attributable probably to their 
wandering owing to hunger. The experiments with lice upon a polychrome 
carpet afforded no evidence of a preference for any particular colour on the 
part of the insects. 
2. THE INFLUENCE ON LICE OF TEMPERATURE CONDITIONS IN CLOTHING 
AND THE ABSORPTION OF RADIANT HEAT BY CLOTH. 
Galli-Valerio (xii. 1916, p. 35) was obviously wrong in attributing the reported 
inimical effect of black clothing to colour, for black is not a colour. A priori 
it appeared to me most probable that the effect would be found to depend 
upon the greater power of absorbing radiant heat possessed by black clothing 
when compared to* that made of various coloured fabrics, it being a matter of 
common knowledge that black clothing may be intolerably hot when worn by 
persons exposed to the sun. White is worn in the tropics or summer because 
it reflects the heat rays that are to a greater or less extent absorbed by black 
and coloured fabrics. 
The difference in the heat-absorbing capacity of clothing materials was 
studied by Krieger 1 , who found that white fabrics (cotton, wool, etc.) acted 
very similarly. When their behaviour was compared to that of various 
coloured or black materials, a distinct difference was observable. If a white 
fabric be taken as 100, the following showed an ascending scale of absorbing 
power for radiant heat: pale sulphur yellow 102, dark yellow 140, light green 
155, dark green 168, turkey red 165, light blue 198, black 208. 
In this connection, I would refer the reader to Parasitology, x. pp. 89-92, 
132, wherein the climatic conditions prevailing in clothing are considered and 
it is shown that a rise in temperature to ca. 35° C. may be distinctly inimical 
to lice (30-32° C. being favourable), that owing to the high temperature near 
the body in summer the insects tend to wander out upon ordinary garments, 
and that for the same reason they wander away from persons in fever. 
Moreover, it has been noted (Ibid. pp. 90, 579) that persons leaving temperate 
climates for the tropics may become freed from body-lice. 
Experiments. 
A double thickness of black serge was cut in the shape of a circle, one-half 
was covered and the other lined with white linen and the whole stitched 
together to form a mat fitting into a glass dish which rested on a black back¬ 
ground. A number of lice were distributed evenly over the bottom of the 
dish and exposed to the sun’s rays after the mat had been placed over the 
lice. Two experiments were made on a warm day with a total of 54 lice: 
1 Cited by Kratschmer in WeyVs Handb. d. Hyy. i. p. 379, Jena, 1899. 
