INSECT ENEMIES OF EASTERN FORESTS 243 
M. robiniae so closely that for present purposes it need be separated 
only by its habits, although the larvae can be distinguished from 
those of M. robiniae by having oval instead of circular spiracles. Dur- 
ing the entire winter the pupa is found in the wood. It is of a yellow- 
ish color with darker, rather greenish, markings on the wing pads and 
small chitinous points on the dorsal surface of the segments. The larva 
feeds in freshly cut wood, exuding large quantities of granular frass. 
It attacks hickory and occasionally Osage-orange, hackberry, grape, 
and ash throughout the Eastern and Central States. 
Very early in the spring, when the leaves are first unfolding, adults 
are found laying eggs beneath scales of the bark on logs cut in the 
winter. For about 8 weeks the larvae feed beneath the bark and then 
enter the sapwood and later the heartwood, where they excavate deep 
mines. AJ] the frass is exuded through a small hole, which is enlarged 
as the larva grows. Early in the fall the matured larva pupates 
behind a wad of fibrous frass at the end of the larval mine. It over- 
winters in the pupal stage, the adult emerging through the exuda- 
tion hole. Hickory cordwood cut in the winter and held over the sum- 
mer is injured, and by the middle of the summer it may be completely 
riddled and the spaces between the ricked sticks of wood filled with 
the exuded dust. Rustic work put up during the winter is ofttimes 
injured. The adults frequently emerge from wood stored for fuel in 
warm cellars and cause annoyance. 
The locust borer (J/egacyllene robiniae) is a medium-sized, robust 
beetle from 14 to 18 mm. in length, black marked with yellow cross 
bands (fig. 52, B). One of those on the elytron is W-shaped. The tho- 
rax 1s wider than long. The larva (fig. 50, 6) is short, robust, and sub- 
cylindrical, having the head wider than long, the apex of the mandible 
rounded, and three pairs of small black ocelli. It feeds beneath the 
bark and in the wood of living black locust trees, exuding the frass, 
and is now distributed practically throughout the United States except 
possibly in California and Oregon. 
In the fall when the goldenrod is in full bloom, the adults are found 
feeding on the pollen of this plant. They lay the eggs beneath the 
bark scales of black locust, the young larvae hatching before the leaves 
fall and overwintering in the outer corky bark. During early spring 
they feed in the bark, and the sap flowing freely from the wound indi- 
cates their presence. About the time the new folhage appears they 
bore through the bark and enter the wood, where they continue to 
feed. Extensive mines are made through the heartwood (fig. 53) and 
the granular frass is exuded through a hole marking the point where 
the egg was laid. In July the larva pupates behind a wad of fibrous 
frass at the end of its burrow and emerges about the time the first 
goldenrod is in bloom, coming out through the hole maintained for 
the exudation of frass. 
The locust borer is the most serious pest of black locust. It has in 
the past destroyed thousands of acres of plantations and greatly dis- 
couraged the planting of this valuable tree. Locust has the ability to 
do fairly well on poor, run-down soils; consequently, it is widely used 
to reclaim waste land and to stop erosion. Borer attack does not in- 
terfere with these uses, but it does prevent the realization of com- 
mercial products such as posts and poles. Plantations are seldom 
attacked until the fourth or fifth year, after which the injury increases 
