56 
tion to beer mash as a cultivating fluid. If one boils a little of this 
in a flask, and, after cooling, sows 1t with spores, a rich mycelium 
develops, both within the fluid and upon its surface, and this pro- 
duces the spores again. ‘’o guard against the invasion of other 
fungi, which will ordinarily suppress the Isaria growing outside the 
body of the insect, the flask must be stopped with a little disinfected 
cotton or asbestos.” 
By Dr. Shimer, the enormous destruction of chinch-bugs in 1-66 
was ascribed to the indirect effect of the wet and cool weather. By 
Mr. Walsh, who discredited the idea of an epidemic or contagious 
disease, it was accounted for as the direct effect of moisture.* The 
phenomena connected with the action of parasites, which [ have above 
described, were apparenty independent of any appreciable general 
cause, as they were most manifest at a time when the weather had 
been warm, dry, and altogether unexceptionable for from one to two 
months. It is not unlikely, however, that wet weather may have the 
effect to stimulate the development of this parasite, either directly 
or indirectly—a hypothesis which will reconcile all the facts. now 
known, as well as the conflicting explanations of them which have 
been hitherto put forth. 
The most important facts under the head of natural enemies may 
‘be thus recapitulated : 
The chinch-bug is subject to attack by all the common lady-bugs 
(Coceinellide) and their larve, by a common predaceous ground 
beetle (Agonoderus comma), by the larva of the lace- wing fly, and 
by one of the robber-bugs (Harpactor cinctus). A number of Cocci- 
nelide, however, captured among the chinch-bugs, were shown by 
dissection to have taken only about eight per cent. of their food 
from these insects, the remainder consisting of plant-lice, spores of 
molds and lichens, and the pollen of flowermg plants; while the 
predaceous ground-beetle mentioned (Agonoderus) was found to have 
derived about one-fifth of its food from the bugs, and the remainder 
partly from other insects, but chiefly from the tissues of ordinary 
plants. A few common birds are shown to feed upon chinch-bugs 
occasionally. The joint effect of these various ordinary enemies 1s 
not necessarily insignificant, but is certainly of no great present 
importance. 
On the other hand, a much more important role is apparently 
played by certain obscure parasites, not previously detected. One 
of these is a minute bacterium (Micrococcus insectorum, Burrill,) m- 
festing the alimentary canal, closely allied to the micrococcus found - 
in the stomach and intestines of silk-worms, and now known to 
cause some of the destructive diseases of that insect. From the 
fact that these parasites were extremely abundant in specimens from 
a field where the bugs were rapidly dying, while in those from ad- 
jacent fields there were relatively very few, it was considered prob- 
*American Entomologist, Vol. I, p. 175, 1869. 
