11 



liquid flows out. Flacherie kills the older more quickly than 

 the younger caterpillars. Young caterpillars, indeed, often 

 live several days before they are killed by the disease. It is 

 not positively known what organisms produce Flacherie. The 

 bodies of caterpillars which have died of this disease show ex- 

 tremely small bacilli, innumerable schizomycetes, and, more 

 particularly, many small strings of micrococci; but which of 

 these micro-organisms, if any, is the real carrier of the disease 

 is still unknown to specialists. 1 To the investigations of Dr. 

 E. Fischer, in Zurich, Switzerland, we owe considerable infor- 

 mation regarding the primary causes leading to Flacherie, and 

 the manner in which the disposition to this disease may be in- 

 duced. He has pointed out that a decrease in the nutritive value 

 of the food of the caterpillars, which induces a disturbance in 

 their metabolism, is the first condition leading to the contraction 

 of the disease. As a result of these disturbances the organisms 

 responsible for the disease immediately find conditions suitable 

 for their growth. One of the main causes of the disease is 

 therefore to be sought in the predisposition of the caterpillars, 

 while the specific infection of Flacherie is to be regarded as 

 coming more or less secondarily; in other words, without this 

 predisposition infection cannot take place, and the predisposi- 

 tion can be brought about artificially by insufficient nourish- 

 ment. 2 Flacherie seems to be influenced by climate and weather 

 conditions less than any other caterpillar disease. We meet 

 with it both in the old and the new world, in wet, in dry and in 

 normal weather. As a result of its comparatively great abund- 

 ance and its extremely easy infection, Flacherie has become the 

 " guardian angel " of the Central European forests. When the 

 " nun " (Psilura monacha) makes its appearance in some places 

 in Europe in vast numbers, man with his wit and the powerful 

 means at his command is quite unable to stop the destruction, 

 but Flacherie always comes to his assistance. Although this 

 disease has been much studied, it has not yet been positively 



1 Very recently C. Sasaki, in Tokyo, Japan, found that there were also polyhedral corpuscules 

 present in caterpillars which were sick from Flacherie ("Deutsche Entomologische National- 

 Bibliothek," Jahrgang II., 1911, No. 1, Referat). Since polyhedric corpuscules, however, are 

 found chiefly in caterpillars which have been infected by the pe'brine, a close relationship of these 

 two diseases is highly probable. 



* See Fischer's detailed accounts in the " Biologisches Centralblatt," Band XXVI., No. 13-16. 

 Leipzig, 1906. 



