FOREST IMPORTANCE OF MYELOPHILUS MINOR HART. 215 
segment of the thorax, i.e. the metanotum, can he seen showing through them as 
a dark triangular area, whereas in M. piniperda the elytra are coarser and not 
so transparent and no such dark area can be seen, although of course on removal 
of the elytra the metanotum is visible. At first it seems to be quite impossible 
to distinguish the two species with the naked eye, yet with a little practice the 
two beetles can be readily distinguished. If the insects be held between the first 
finger and thumb and be looked at sideways, the apical part of the elytra of 
M. minor appears shiny all over, since there are no hollowed-out portions on the 
second interstices. . On the other hand, the apical part of M. piniperda held in a 
similar position appears shiny, except at the second interstices of the apical portion 
of the elytra ; there it appears dull, due to the hollowing out of the second interstice 
on each side of the suture. This character is undoubtedly the chief differentiating 
character between the two species. 
Sexual Differentiation in M. minor. 
It is difficult to distinguish the two sexes of this beetle by external characters, 
yet with the aid of a binocular dissecting microscope the following differences can 
be noted : — 
(1) The under surface of the last segment of the abdomen in the female is 
markedly convex from front to rear, while in the male this same part appears 
flattened or slightly concave. 
(2) The ventral surface of the abdomen is much more convex from side to side 
in the females than in the males, in which the ventral surface is- flattened. 
These same two characters can be safely relied on for differentiating the sexes 
of M. piniperda. 
A further aid in distinguishing the sexes in M. piniperda, pointed out by 
Eichhoff,* is that the apical part of the second interstice is narrower, deeper (more 
hollowed out) in the male, and in the female broader and shallower. I have 
repeatedly tested this and' found it a most useful character. 
Egg of M. minor. 
The egg is oval in shape, smooth, and in colour shining white. It measures 
1 mm. 
The eggs of M. piniperda and M. minor are indistinguishable. 
Larva of M. minor (fig. 8). 
The larva of M. minor is a typical Scolytid larva, and is well adapted to its 
mode of life. It is a soft, cyclindrical grub, legless, with curved body. The colour 
is yellow-white, except the hard chitinous head and mouth parts, which are dark 
* W. J. Eichhoff, Die europaischen Borkenkafer, p. 101. 
