11 
of seeds in more highly organized plants. The practical value 
of a disease-producing fungus depends largely upon its ability 
to grow on other material than insects, or in other words, on 
the ease with which it can be artificially cultivated, aside, of 
course, upon its fatal character to the insects themselves. It 
also depends very largely on the habits of the insects on which 
it grows. ‘Thus social insects are more liable to epidemics 
than solitary species, for in social species a constant contact 
with the diseased objects as well as with the other members of 
the same colony greatly facilitates the spread of the disease. 
This explains, in part, why a disease will spread much more 
rapidly, and work more effectually, when insects occur together 
in large numbers, than when few and scattered. The same 
thing occurs when an epidemic of yellow fever or cholera 
sweeps through our land. How much more quickly and fatally 
it works in our cities than in thinly populated regions! Some 
of these diseases seem to force their victim to wander about, 
and thus spread them in all directions. Thus grasshoppers 
attacked by the Grasshopper-fungus (Zmpusa grilli Fres. ), 
invariably climb some tall weed or grass, and cling to it long 
after death. 
Figure 4 shows a grasshopper 
(Melanoplus bivittatus Say.), which 
has been attacked by the fungus 
and killed after it had climbed to 
the top of a plant. The figure 
shows well the frantic efforts of 
the grasshopper to cling to its 
support. This peculiar effect of 
the disease enables its spores to 
infect a much wider area, as they 
can from this elevated position fall 
on the food of the grasshoppers 
as well as on the grasshoppers 
themselves. This fungus has also 
the power of throwing its spores 
to a considerable distance. <A 

P 4 Fig. 4.—Melanoplus bivittatus. 
chinch-bug when it feels the first ined by a tungus. Original. 
effects of the Sporotrichum, usually seeks some cool, shady 
