The Genus Hylastes, Er. 129 
From the ventral aspect the mesothorax is seen to be divided into 
prosternum, mesosternum and poststernum, while the episternum and epimeron 
are again visible. The prosternum is a narrow area divided from the 
mesosternum by a linear impression. The wmesosternwm occupies the 
remainder of the mesothorax, except for a small trapezoidal area lying 
between the coxe. ‘This represents the poststernwm. 
The Metathorax.—TYhe regions of the metathorax are somewhat com- 
plicated and are best indicated by the figures. The three regions—prescutwm, 
mesoscutum, and postscutwm—are visible dorsally on the removal of the wings 
and the elytra. 
Viewed ventrally, the epimeron and the various areas connected with 
the wing attachment are visible together with the long narrow episternum. 
On the under surface, the sternum occupies nearly the whole of the area. 
It bears a well-marked, median line, running from its anterior to its posterior 
borders. A small irregular, triangular piece lying between the coxe 
represents the poststernum. 
Wings and Appendages. 
The elytra or first pair of wings are attached to the prescutum. They 
are distinctly furrowed, the furrows being further deepened by rows of 
circular pits. The stviw are roughly crenate. The wings are attached to 
the metascutum and are of the typical Scolytid type. 
Legs. 
All the usual joints are present in the legs of Hylastes. The three 
pairs of legs are all somewhat similar in structure. They vary in 
two respects—in the shape and position of the cox and in the tooth-like 
projections on the outer margin of the tibiz. 
In the first pair of legs the coxe are almost contiguous. They are 
roughly circular and very prominent. The tibiz are shorter and broader 
and bear six teeth on the outer margin. 
In the second pair of legs the coxe are more oval, less prominent than in hs 
first pair and slightly wider apart. The tibiz are slightly longer and narrower 
than in the first pair of legs and bear seven teeth on their outer margin. 
The coxze of the third pair of legs are only slightly prominent. They 
are almost contiguous and extend laterally to the wing covers. The 
tibiz of the third pair of legs are longer and narrower than in the others. 
They bear on their outer margins a series of small teeth variable in number, 
followed by seven or eight more prominent teeth. It should be observed 
that by the articulation of the trochanters and cox the legs are capable of 
a pivot-like movement. 
