G-. H. F. Nuttall 
171 
body by the wristlet method, the longest life of a male was 23 days, of 
a female 22 days; the experiment should, however, be repeated in cool 
weather, for I believe they will live longer. 
Therefore the females usually outlive the males. .The longest lives 
observed by me in corporis (and capitis) are markedly shorter than those 
recorded by Sikora and Bacot, the age of the females in both cases 
falling 5 days short of Bacot’s average. The reason seems clear when 
we consider that my females laid more eggs per day, their metabolism 
being necessarily more active under the more natural conditions in 
which they were maintained. Under approximately like experimental 
conditions, corporis lives some days longer than capitis. 
Feeding Habits. 
The act of sucking blood was first, observed microscopically by 
Robert Hooke (1665, pp. 211-213), who mentions that it is accomplished 
by a “pump” in the head 1 . Leeuwenhoek (ed. 1807, p. 163) relates 
that the louse everts a nipple-like protuberance from the front of the 
head from which the piercing organ issues; the latter being enclosed 
in a retractile sheath. Leeuwenhoek describes how the louse raises the 
posterior portion of its body when feeding; in the absence of hairs it 
clings firmly by its sharp claws to the skin surface; the blood is seen to 
flow through the oesophagus whilst the intestine shows active peristalsis. 
The process of feeding was also observed by Swammerdam (ed. 1682, 
p. 60) who described how he saw the blood flow like waves into the gut, 
recalling the rush of water through a sluice; the blood entered with 
such force that the excreta were propelled outward, whilst the gut 
moved actively. 
Various matters relating to the mechanism of feeding will be con¬ 
sidered in detail in the section dealing with the mouthparts 2 . Regarding 
the general behaviour of lice when feeding, little has been added to what 
was so well observed by the old authors just mentioned. Having 
anchored itself firmly upon the skin or by clinging to the base of one 
or more hairs, the louse feels about with its head depressed. The 
object of depressing the head is to permit the teeth of the haustellum to 
penetrate the skin. The haustellum, or “nipple-like protuberance” of 
Leeuwenhoek, is provided with rows of dorsally projecting recurved 
1 Nevertheless Widmann (18. vm. 1915, p. 290) makes the absurd statement that the 
blood is sucked up by “gut peristalsis” ! 
2 Lice refuse to feed on a drop of blood (Widmann, 28. ix. 1915; Galli-Valerio, 9. v. 
1916, p. 37). 
