THe Hoc LovusE CALs 
nations respectively of the transverse conjunctivae between the pro- and 
the mesothorax and between the pro- and the mesosternum. 
A second structure hitherto undescribed in the Siphunculata is found 
in the. head, under the posterior lobes of the brain. The position and 
structure of this pair of bilaterally symmetrical circular bodies suggests 
their interpretation as the ‘ corpora allata”’ of Heymons and other 
investigators (cited by Berlese, 1909:588, and by Schréder, 1912-13:86). 
In the study of the stomodaeum and the mouth parts, the aim has been 
to present as accurate a picture as possible of their anatomical structure, 
musculature, and working. Their homology is not touched upon, because 
in the case of structures so far modified from the generalized type, inter- 
pretation should rest upon an investigation begun with the earliest 
appearance of segmentation in the embryo and continued to maturity. 
Cholodkovsky (1903:120) alone has touched upon this aspect, in his 
work on the man-infesting pediculi, whose pharynx and mouth parts are 
similar in plan to those of the hog louse. In none of the sections of the 
alimentary canal have protozoan parasites been found, and the physiology 
of digestion has been touched upon but briefly. 
The reproductive systems and the secondary sexual characters resemble 
those of other members of the order, but in the female no receptaculum 
entering the uterus has been found. According to Harrison (1916 b:221), 
“in the Ischnocera, and in all Anoplura save Pediculus, a receptaculum 
of remarkable structure opens into this uterus by a long narrow duct, 
the entry of the duct into the reeeptaculum being marked by a conspicuous 
chitinous ring.” 
The experimental work on the biology of the species has been carried 
out with much care. In the acceptance of the resulting figures indicating 
periods in the life history, however, it must be borne in mind that in the 
natural habitat, with continual opportunity of feeding, these periods 
may be somewhat shorter. 
ACKNOWLEDGMENTS 
Thanks are due to Dr. V. A. Moore, of the New York State Veterinary 
College at Cornell University, for facilities for keeping a hog for experi- 
mental work; to the Department of Entomology of the New York State 
College of Agriculture at Cornell University, for the payment of the 
expenses connected with keeping the hog; to the Department of Animal 
