INSECT ENEMIES OF EASTERN FORESTS Dla 
matured larva makes an upward excavation extending outward toward 
the bark for a pupal chamber. The adult gnaws the exit hole. 
Above 7,000 feet in the Rocky Mountain region extensive areas of 
aspen are destroyed by these larvae. In many places 90 percent of 
the trees are found to be attacked each year, some breaking off during 
the winter storms. Following severe ice storms stands have been 
examined where nearly every tree was felled and each showed the hol- 
lowed butt, where it was broken. It would be impractical under pres- 
ent forestry conditions to attempt the control of this insect, as both 
the stumps and roots would have to be removed to destroy the larvae. 
The rustic borer (Xylotrechus colonus ¥.) is a dark-brown beetle 
from 8 to 17 mm. in length with irregular variable whitish or yellowish 
markings. The larvae are found under the bark of almost all dead 
hardwoods; in fact, it is one of the commonest of all cerambycids in the 
Eastern States. Y. sagittatus (Germ.), a somewhat larger species, 
from 15 to 20 mm. long, is hghter-brown in color. It bores in the wood 
of most conifers, particularly pine, and in many localities where pine 
predominates is the most abundant wood borer, with the exception of 
Monochamus spp. 
FamMiry CHRYSOMELIDAE 
THE LEAF BEETLES 
By H. J. MacALonry 
The leaf beetles, or chrysomelids as they are sometimes called, belong 
to a very large family which is closely related to the roundheaded 
borers, there being no definite and constant differences. As a rule, 
however, the adults are very different in general appearance; usually 
they are medium-sized or small, short-bodied, and more or less oval in 
shape. The legs are generally short; but in some species the femora 
of the rear pair are enlarged, thus fitting them for Jumping. There 
isa great variation in coloration and markings. More commonly the 
adults are spotted or patterned in brightly contrasting nonmetallic 
colors, but some have a bright metallic sheen on the thorax and elytra; 
still others are dark or straw-colored. In some cases the coloration 
varies greatly within the species. Many species are hairless, whereas 
others are pubescent or are covered with scales or scalelike hairs. 
The larvae are usually soft-bodied and frequently have highly pig- 
mented or well-chitinized sclerites on the integument. They are 
usually free living, except the leaf miners, root feeders, and case- 
bearers, and the form varies greatly from short and compact to de- 
pressed cuneiform.in the leaf miners. The head is usually protuberant, 
except in the leaf miners, and bent down for. feeding. There is no 
hypopharyngeal bracon, the mandibles are of the biting type without 
a molar structure, the gula is soft and fleshy, and the, ventral mouth 
parts are compacted into a unit with the maxillary sclerite indistinct 
or fused, and not cushioned as in the Ptinidae, Cerambycidae, and 
related families. The legs are usually well-developed, five-jointed, or 
occasionally wanting: the ninth abdominal segment sometimes bears 
paired processes, and the tenth segment is small. 
792440°—49—__18 
