8 



those known to occur in the silkworm (Bombyx mori) and in 

 the " nun " moth (Psilura monacha), which latter destroys the 

 forests of Central Europe. 



The first scientific knowledge which we have of caterpillar 

 diseases we owe to the valuable investigations of the French 

 scientist Pasteur. Since his time many other investigators have 

 been engaged in this study, among them the Germans Standfuss 

 and Emil Fischer, the Italians Verson and BoUe, and the 

 Americans Snow and Forbes. By their experiments and in- 

 vestigations we are now able to recognize the character of the 

 more common caterpillar diseases. 



We may mention some of those diseases with which the 

 lepidopterist will come in contact in the course of a few years. 



A very frequent disease of caterpillars is the common 

 diarrhoea, which is produced in most cases by too juicy or too 

 wet food. This is shown by the unusually wet excrement, the 

 fluid part of which is green. If the disease is of longer stand- 

 ing, the excrement does not cling together, but is voided as a 

 pnlpy mass, in which the single vegetable particles swim around 

 undigested. This disease in itself is not dangerous, since it 

 is not infectious, but it may prepare the way for the attack of 

 other infectious diseases, which will be mentioned further on. 



In another disease, which has no popular name as yet, and 

 which I shall call head disease, the excrement masses hang 

 from the body like a string of beads. This intestinal disease 

 is probably due to unhealthy food, but the specific cause has 

 not been determined. Apparently this disease, too, is not 

 infectious. 



Of much greater importance is the disease known as muscar- 

 dine. This is really a collective name for a series of fungous 

 diseases, which convert the infected caterpillar in a short time 

 into a stiff, swollen mass, with the skin invested with a grayish- 

 white coating. Very hairy caterpillars are especially suscep- 

 tible to muscardine, but in extremely wet years even smooth 

 caterpillars suffer from fungous diseases. It is easy to deter- 

 mine whether muscardine is present in a given locality because 

 the diseased caterpillars crawl toward the exposed tops of grass 

 blades, poles or stems, and remain there after death, thus be- 



