12 
spot under a clod of soil, and there dies in the spot usualiy 
chosen by the healthy bugs for a quiet place to shed their old 
skins. The wire-worms attacked by a disease caused by Isaria 
anisoplie Metch. are usually found in bunches of loose vegeta- 
ble matter, in which they die. Possibly they gather there after 
being attacked; at any rate the fungus-growth usually spreads 
from the body of the wire-worm to the vegetable matter, on 
which it grows and spreads. These actions of the insects aid 
in spreading epidemics found among them. Many epidemics 
among insects are useful to man, if noxious insects are the 
sufferers, and it is possible by artificial means to cultivate and 
increase the spores, which cause them, to almost any extent. 
But this is about all that man can do, as he is unable to produce 
at the same time all those conditions that are in favor of the 
parasite. 
The manner in which an insect is attacked by a fungus-dis- 
ease is usually through the skin or breathing-pores, or else by 
eating the pores that found their way toits food. In either 
case the minute spore germinates or puts forth a slender germ- 
tube, which penetrates the skin of the wall of the intestines or 
stomach, and grows into the body-cavity. Here it develops 
by taking food from the juices of the body; sometimes branching 
freely and often breaking up into short segments, until it even- 
tually fills part or all of the body of the insect with a more or 
less firm mass of interlaced fibres. Figure 5 shows the manner 
in which one of the cabbage-worm diseases destroys its victim. 
The death of the insect has generally occurred by this time and 
it only remains for the fungus to provide for the reproduction 
of its kind. This it does by the growth of the threads through 
the skin and the production, on the outside, of spores or con- 
idia born in various ways, sometimes in loose fluffy masses of 
threads, as in the case of the chinch- bug disease, sometimes in 
a more elaborate growth, which, if the insect is subterranian, 
usually reaches up above the surface of the ground; sometimes 
the spores are borne close to the body on the ends of threads 
which barely project through the skin. This is the case with 
the fungus of the common house-fly, as may be seen in the il- 
lustration fig. 2. These spores gain access to other insects, 
and the cycle of growth is repeated until winter or unfavorable 
conditions prevent its further progress. 
