The Hog Louse 671 



been traced between them and the brain, but they are in close association 

 with the tracheoles of the commissure passing under its posterior part. 

 While a study of the texts of Berlese (1909:588) and Schroder (1912-13: 

 86) suggests that these bodies may be homologues of the "corpora allata" 

 described by Carriere and Burger in 1897, Heymons in 1899, Janet in 

 1899, and others, a knowledge of their development is essential for their 

 correct interpretation. A short distance behind the brain and approxi- 

 mately above the esophageal ganglion, there has been seen in longitudinal 

 sections of the head a ganglion in the course of the recurrent nerve, but 

 no branches have been found issuing from it. This may be the hypo- 

 cephalic or hypo-cerebral ganglion figured by Berlese (1909:596). 



No attempt has been made to interpret a peripheral nervous system 

 such as was described by Briihl (1871:477) in the pediculi infesting man, 

 but if the nerve to the antennae be followed, it is seen to give off branches 

 to the second and third segments which end directly under the cuticula 

 in large multinuclear sensory cells similar to those at the termination of 

 the labral nerves. In the terminal segment the nerve breaks up into 

 branches corresponding in number to the blunt spinelike processes on 

 the terminal sensory plate. Each branch terminates under its process 

 as an oblong-ovate multinuclear sensory" cell (Plate LIX, 9),but the actual 

 connections between the cells and the processes have not been seen. 

 Similar sensory cells have been seen in a few sections underlying the 

 hairs of the abdomen. 



THE STOMODAEUM, MOUTH PARTS, AND SALIVARY GLANDS 



Writing of the clothes louse, Sikora (1916:22) says: " Es gibt kaum 

 cin anderes Insekt, liber dessen Anatomic so lange gestritten wurde, 

 und liber das so viele voneinander ganzlich abweichcnde Meinungen 

 geaussert worden waren, wie die Laus." Most of the literature is 

 the outcome of investigations of the man-infesting pediculi, but in some 

 instances more or less detailed comparative studios have been made 

 on the hog louse. With a few exceptions workers have confined them- 

 selves to the study of the mouth parts and their homologies, and this 

 for two reasons: first, because in the middle of the last century a contro- 

 versy was carried on as to whether lice possessed biting or sucking mouth 

 parts, and secondly, because the systematic position of the group, long 

 a matter of uncertainty, was thought to be dependent on the morphological 



