THE GENUS DENDROCTONUS. 
53 
No. 3. THE ROUNDHEADED PINE BEETLE. 
(Dendroctonus convexifrons Hopk. Figs. 15-17.) 
The roundheaded pine beetle is a somewhat elongate cylindrical, 
reddish-brown to black, rather shining barkbeetle, 4 to 6 mm. in 
length, with the front of the head convex, and without frontal groove, 
the prothorax broad, only slightly narrowed toward the head, and 
finely punctured, the elytra with coarse rugosities toward the base, 
and the declivity with fine punctures and long erect hairs. (See fig' 
15.) It attacks injured, felled, and healthy western yellow pine from 
southern Arizona to northern New Mexico and southern Colorado. It 
excavates long, slightly winding, longitudi- 
nal, and sometimes transverse and branched 
egg galleries (fig. 16) extending through the 
inner living and dying bark and grooving 
the surface of the wood. At intervals 
along the sides of the galleries single eggs 
are deposited. The short, cylindrical, grub- 
like larvae extend their larval mines at right 
angles to the egg galleries, usually through 
the inner layers of bark, and mark the sur- 
face of the wood. The transformation to 
pupge and adults is sometimes in the inner 
bark, but probably more often in the outer 
bark. This barkbeetle is nearly always as- 
sociated with one or more of four other 
species of Dendroctonus — Nos. 2, 3, 5, 8, 
and 10. The presence of this species is Fio.is.-The roundheaded pine 
indicated by pitch tubes on the trunk and beetle (Dendroctonus convexi- 
, ,, j. v i i t i j. v frons): Adult. Greatly enlarg- 
by the fading and reddish foliage. ed. (Author's illustration.) 
SEASONAL HISTORY. 
OVERWINTERING STAGES. 
The winter is passed in the bark of trees attacked the preceding 
summer, as parent adults, young to matured larvae, young adults, 
and possibly pupae, the parent adults in the egg galleries, and the 
broods in the outer and inner bark. 
ACTIVITY OP OVERWINTERED BROODS. 
The overwintered parent adults extend the old galleries or excavate 
new ones from the time activity begins in May until the last of June, 
or later. The overwintered broods of young adults begin to emerge, 
probably, in June, and continue to come out until September. The 
overwintered larvae begin to transform to pupae and adults in June 
and apparently continue to develop and transform to adults until 
activity ceases in the fall. Some of the adults which have transformed 
