244 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
for several years until the trees are about 6 inches in diameter. As 
the bark becomes thicker. 
survival of the larvae is lower, and stands 
that escape severe destruction are relatively free from injury after 
FIGURE 5¢é 
of locust tree dying from 
injury by the locust borer 
(Jfegacyllene robiniae). 
reaching this size. The damage results 
from the breaking off of the stems and 
branches weakened by the borer mines in 
the sapwood and heartwood. Moisture is 
probably the governing factor in inhibit- 
ing the surv ival of the young larvae. Dur- 
ing dry springs many larvae survive, and 
stands that have been relativ ely free from 
damage have been observed to be com- 
pletely destroyed following very dry 
seasons. 
No satisfactory control or prevention 
has been developed for this insect. Hall 
(208) pointed out that damage is least in 
rapidly growing stands and greatest in 
slowly growing trees. Avoidance of poor 
sites, except for soil-reclaiming purposes, 
and utilization of measures that tend 
to stimulate growth are recommended. 
Shade produced by dense stands or mixed 
plantings seems to prevent considerable 
damage, especially on better sites. Badly 
damaged stands should be clear cut during 
the winter and allowed to sprout. Coppice 
stands seem to be relatively immune, at 
least for some years. Shade, ornamental, 
and valuable trees should be sprayed as 
recommended on page 26. This insect has 
been further discussed by Craighead (108) , 
St. George and Beal (372), and Gar- 
man GE). 
Desmocerus palliatus (Forst.), the el- 
der borer, is a rather large, elongate, ro- 
bust beetle of strikingly contrasted, bright 
yellow, orange, and blue colors. It has a 
small head narrowed behind into a neck. 
The eyes are deeply emarginate and the 
last joints of the antennae are velvety 
black. The larvae are of shining texture 
and robust form, having the head sub- 
orbicular, wider than long, with three 
ocelli on each side and the mandibles tri- 
angularly pointed. The pronotum is 
rugulose and shining, and the tubercles of 
the ampullae are confluent. The legs are 
well developed. These larvae feed in the 
roots and base of elders, eating out the pith 
and filling the mines with coarse, rather 
fibrous frass, much of which, however, is 
cast out. 
