FOREST IMPORTANCE OF MYELOPHILTJS MINOR HART. 
217 
The prothoracic segment in side view shows the following five folds * : the 
scutellar (Sr.) forming the dorso-lateral portion ; the scntal (Sc.) and the epipleural 
(e.) forming the lateral portion, the latter being more anterior and ventral than the 
former ; the hypopleural (h.) and sternellar (St.) forming the ventral portion, the 
sternellar fold being more ventral than the hypopleural. The scutal fold bears a 
spiracle which is situated in its most ventral part. 
The mesothorax in side view shows six folds : the prescutal (p.) forms the anterior 
dorsal portion; the scutellar (Sr.) forms the dorso-lateral portion; the scutal (Sc.) 
and epipleural (e.) form the lateral portion ; and the hypopleural (h.) and sternellar 
(St.) form the ventral portion. The metathoracic segment is similar to the 
mesothoracic. 
The Abdomen. 
The first seven segments of the abdomen of the larva (c, fig. 8) correspond in 
structure although they vary in size. In side view each shows six folds : the 
prescutal (p.), scutal (Sc.), and scutellar (Sr.) forming the dorso-lateral portion ; the 
epipleural ( e .) forming the lateral portion ; while the hypopleural (h.) and sternellar 
(St.) form the ventral portion as before. 
On each segment lying between the epipleural, and scutal, and scutellar folds there 
is an S-shaped groove in the anterior dorsal side of which lies a spiracle (Sp.). 
The 8th abdominal segment is similar to the first seven, except that there is 
no prescutal fold ; the scutellar fold is just traceable. The 9th abdominal segment is 
similar to the 8th, only it bears no spiracles. The 10th segment in side view shows 
three lobes surrounding the anus : the infra-anal lobe (i.) is situated ventral to the 
anus, the supra-anal (Su.) dorsal, while the para-anal (pa.) is between the above two. 
In a ventral view of the larva two other folds may be seen, namely, the sternal 
and poststernellar. These two folds are present in all the segments of the thorax 
and abdomen, except in the last three of the abdomen. In the 8th and 9th the 
poststernellar is absent, while in the 10th both are wanting. The sternal fold com- 
prises the anterior central portion of the ventral surface of each segment, while the 
poststernellar lies posterior to the sternellar. The poststernellar comprises the 
posterior portion of each segment ; only the lateral portions of this fold are visible 
in the prothoracic segment. 
Comparison between Head of Larva of M. minor and M. piniperda. 
After careful microscopic examination of numerous preparations of the head and 
mouth parts of the two different larvae, I have come to the conclusion that there is 
no satisfactory differentiating character. I have examined the parts mounted and 
unmounted, under cover-glasses where the pressure had the tendency to move the 
* In this description of the larva I have followed the terminology of Hopkins, “ The genns Dendroctonus ” 
U.S. Bureau of Entomology, Bulletin No. 83, part i,- p. 11, 1909. 
