THe Hoa Louse 649 
The last data relate to a female reared in captivity. Three days after 
the last molt, when put on the arm to feed, she moved rapidly about 
for thirty minutes, repeatedly elevating the posterior end of the abdomen, 
and made no attempt to draw blood. She was returned to the vial and 
two hours later was given another opportunity to feed, when an egg was 
found attached to a bristle in the vial. Twice a male was placed in the 
vial for some hours, but in neither case was copulation seen to occur. 
During a period of sixteen days eighteen eggs were laid, none of which 
hatched. The female died six days after laying the eighteenth egg, and 
gross dissection showed the ovaries very much shrunken. That oviposition 
continues without fecundation has been observed by various workers, 
and the unfertilized eggs are easily recognizable because they quickly 
change color and shrivel up. 
When laid, the egg is an iridescent pearly white. As development 
progresses it becomes more opaque, and toward the end of the incubation 
period it appears light amber in color. Its average length is 1.5 to 1.75 
millimeters, and its average breadth at the widest part is 0.5 to 0.75 milli- 
meter. It is symmetrical, tapers posteriorly, and is bluntly rounded at the 
anterior end, where the operculum is situated. The widest part is just behind 
the operculum (Plate LVIII, 2). The surface is covered with small puncta- 
tions, which are somewhat larger on the operculum than on the main part 
of the egg. The junction of the egg with the operculum is indicated by a 
small ridge bearing striations parallel to the longitudinal axis of the egg. 
Hatching has not been observed, but eggs have been seen shortly after 
being hatched. The operculum opened away from the bristle and remained 
attached to the egg by a small hinge; protruding from the egg was a small 
fragment of the vitelline membrane (Plate LVIII, 2). A number of authors 
have mentioned points in connection with the hatching of pediculi infesting 
man, and Sikora (1915:530) was the first to give a short description of 
the process, which has since been confirmed and extended by Nuttall 
(1917 d:148). Probably in the hog louse the process is essentially the 
same. The following data show that the period of incubation is influenced 
by temperature, and suggest a reason for the seasonal variation in the 
development of the eggs on the hog: 
Conditions Eggs hatched after Authority 
On hog © About 5 days Coburn‘ 
4 Data from Coburn (1888). 
