THE CHERRY LEAF-BEETLE. 5 
season had undoubtedly been favorable to the development of un- 
usual numbers of these beetles—as much as their native host plant 
could support. Furthermore, the foliage of the pin cherry was reduced 
by a freeze on May 27, and perhaps in a part of the range by tent 
caterpillars also. Similar conditions were probably responsible for 
the outbreak in Michigan. These conditions induced a migration 
which was given direction by a strong wind that blew from the south- 
east and south on June 5, 6, and 7. It is probable that the majority 
of the beetles had emerged from hibernation and had been feeding 
for some time before their advent in the grape belt, for an outbreak 
was reported from Jamestown, N. Y., about 25 miles south of Lake 
Erie, as early as May 12. 
Within a few days after their arrival the numbers of the beetles 
began to decrease in some orchards, and in two weeks this was gen- 
eral. By the latter part of June practically all had disappeared from 
the orchards, although a few scattering ones were found as late as 
early August. 
CAUSE OF INCREASE OF BEETLES. 
The increased numbers of the cherry leaf-beetle may be attributed 
to an increase in abundance of its natural food plant, the pin cherry. 
This tree springs up rapidly along roadsides and in cut-over or fire- ° 
swept forest land which has been left uncultivated. Such lands cover 
wide areas in western Pennsylvania, and furnish ideal breeding con- 
ditions for the beetle. A typical view of such a situation is shown 
in Plate I. 
FEEDING HABITS AND DESTRUCTIVENESS. 
The adult cherry leaf-beetle feeds almost exclusively on the under- 
side of the leaves of the plants attacked (Pl. V, C, D), eating small, 
wregular holes through the lower epidermis and parenchyma and 
sometimes through the entire leaf. These holes may join one 
another or come so close together as to skeletonize the leaf. Ina 
few days after feeding, the upper epidermis thus exposed dries and 
falls out, and, in case of severe injury, the whole leaf dries, and 
defoliation ensues. To an extent it feeds also upon the fruit of the 
cherry, scarring and pitting it. (Pls. III, IV.) 
On cold days and at night the beetles crowd on the upper surface 
of the leaves, and hence have given the impression that they feed 
there. Occasionally the writers have found beetles feeding on the 
upper surface of peach leaves, usually those attacked by leaf curl, 
and once on the upper surface of cherry leaves. The misapprehen- 
sion in regard to their feeding on plum has been discussed in an earlier 
paragraph. The shot-hole fungus, responsible for this mistaken 
belief, also attacks other stone fruits which the beetle attacks, and 
