1914] Tower—Mechanism of the Mouth Parts of the Squash Bug 99 
the -angles. I have seen such men months afterwards with the 
calves of the legs and the ankles discolored as though the limb had 
been beaten or severely bruised. It may.be stated in this con- 
nection that pellagra was not at that time recognized in this 
country. 
- 
THE MECHANISM OF THE MOUTH PARTS OF THE 
SQUASH BUG, ANASA TRISTIS DEGEER} 
By Dantet G. Tower, B.S., 
In preparing a previous paper dealing with the external anatomy 
of the squash bug (Tower, °13) it was found necessary to work 
out the structure of the mouth parts and internal anatomy of the 
head region. The mouth parts proved to be so interesting that 
a study more detailed than was possible in a general consideration 
of the anatomy has been made, the results being incorporated in 
the present paper. A brief description of the external region of 
the head and its parts has also been included so that one may more 
readily orient himself as to the relation of the parts to one another. 
At this point I wish to thank Dr. H. T. Fernald for his assistance 
and the loan of books and pamphlets from his private library; 
and Dr. G. C. Crampton, who has directed my work and greatly 
assisted me in preparing this paper for publication. 
As the sclerites of the head capsule are solidly fused together 
the general regions are all that can be described. Of these the 
occiput (occ), see Pl. 1 f. 1, lies behind the ocelli (oc) and forms 
the posterior portion of the head surrounding the occipital fora- 
men. It is marked off by a shallow transverse groove, from the 
vertex. The vertex or cranium (v) comprises the dorsal region 
in front of the occiput and bears the ocelli. This area is not marked 
off from the frons (f), which lies above and between the bases of 
the antenne. The anterior margin of the frons is united with 
the base of the clypeus (c). 
Below and on either side of the compound eyes (e) lie the gene 
(g), while the ventral posterior portion of the head capsule forms 
1 Contribution from the Entomological Laboratory, Massachusetts Agricultural College. 
