. 12. Contagious Diseases of the Chinch-bug. 
ber of other insects as well, and probably never dies out entirely over any large 
area of the state, but is always sufficiently prevalent and common under all con- 
ditions to furnish a suitable beginning for a spontaneous spread wherever an in- 
sect species, like the chinch-bug, becomes for a time superabundant under 
conditions favorable to the growth and reproduction of the fungus characteristic 
of this disease. 
‘*2. The conditions necessary to its appearance among chinch-bugs on the 
epidemic scale are an abundance of the bugs themselves and a considerable 
amount of wet weather, with not too low an average temperature. 
**3. Its hidden presence among bugs which, as observed in the field, seem to ~ 
be wholly free from it may often be demonstrated by shutting up such bugs for 
two or three days in a moist atmosphere; but, on the other hand, as this pro- 
cedure often fails to develop it, it is not always and everywhere present. 
‘‘4. Its characteristic fungus may be easily cultivated on certain mixtures of 
animal and vegetable substances, or on either of these substances alone — plain 
beef broth or simple agar-agar, for example. The cheapest and most satisfactory 
mixture thus far used is corn-meal saturated with beef broth. 
«5. It can only be grown on these media in the absence of the germs of fermen- 
tation and decay. If these are not excluded, they take possession of the surface, 
and the muscardine fungus will not grow in competition with them; methods of 
sterile culture are therefore indispensable. The most convenient apparatus of 
sterile culture used by us is a circular copper pan, nine inches across and one 
inch deep, with straight sides, and a cover which shuts over the pan like the lid 
of a pill-box. A less convenient but slightly safer apparatus is a Mason fruit-jar, 
with the metal cap altered by the insertion of a tube, which may be plugged with 
cotton, as a protection against bacteria and other fungus germs. 
‘*6. Propagation of this fungus to living insects is easy if the atmosphere is 
kept moist. We have found as yet little, if any, reason to believe that the cul- 
tivated Sporotrichum is any less active as an agent of infection than that 
grown on the insect body. Its spores will germinate on the surface of in- 
fected insects, sending their thread-like outgrowths through the cuticle; but 
soft-bodied forms, like caterpillars, are, as a rule, more easily infected than those 
with a hard crust. 
“7. The distribution of the Sporotrichum in the field will have no immediate 
effect if the weather is dry, but spores may live in a dry state for many months, 
and may thus give origin to an outbreak of muscardine, if the weather changes, 
long after they have been distributed. 
‘8. The readiest and most convenient method of rapid propagation and gen- 
eral distribution of muscardine is to grow the fungus on corn-meal batter mixed 
with beef broth by the sterilization methods of the bacteriological laboratory, 
and to distribute this cultivated fungus to farmers, with instructions for its use. 
For its dissemination in their fields, chinch-bugs are to infected by exposure to ~ 
the fungus in tight wooden boxes, with a layer of earth in the bottom of each 
box. The imprisoned bugs must be supplied with food, which should be renewed ~ 
as necessary, and the contents of the boxes must be kept continuously moist. As 
the bugs show evidence of disease, a part of them are to be scattered in the fields 
at intervals, their places being taken by fresh bugs put in the box. This opera- 
tion is to be continued until the desired result appears. A more convenient 
method, and one less liable to miscarriage through failure of the farmer to carry 
on successfully operations for the propagation of the fungus, is the cultivation 
of spores in sufficient quantity to permit their direct application in the field. 
This would require, however, a very large central plant for cultivation and dis- 
