MICROBIAL DISEASES OF INSECTS 935 



entertained that sacbrood will be transmitted by the hands or clothing 

 of the operator, by the tools used about the apiary, through the medium 

 of the wind, or by the queen. Flaming or burning the inside of the 

 hive, or treating the ground about a hive containing a sacbrood infected 

 colony appears to be entirely unnecessary. 



WILT DISEASE OR FLACHERIE or THE GIPSY MOTH CATERPILLAR, 



Porthetria dispar L. 

 Filtrable virus Glaser* 



HISTORY AND DISTRIBUTION. There is no account of the occurrence 

 of wilt in America prior to 1900. This disease may have been intro- 

 duced on trees or shrubs imported from Europe, in which country 

 'Wipfelkrankheit," a wilt disease of the European nun-moth cater- 

 pillars, Psilura monacha, exists. In Europe flacherie has become the 

 "guardian angel" of the central European forests. 



In the United States there is every reason to suppose that the wilt 

 is distributed over the entire territory infested by the gipsy moth, a 

 territory of about 4,850 square miles (1915) extending over various 

 parts of Maine, New Hampshire, Massachusetts and Rhode Island. 



SYMPTOMS. The symptoms of the wilt disease of the gipsy moth 

 caterpillars are those of flacherie of the silk- worm. They soon stop 

 eating, become languid, usually crawl up on some object where they 

 remain motionless. In a few hours there drops from the mouth and 

 anus a dirty, blackish, foul-smelling liquid; they become more and more 

 flaccid, one leg after another looses its support and finally the cater- 

 pillar reduced to a black skin is found hanging limply to tree trunks 

 and limbs, still holding on with one or two of its false feet or with the 

 anal claspers. After death their body tissues become degenerated so 

 rapidly that it is impossible to handle them; a slight touch breaks the 

 skin and a thin dark, offensive-smelling liquid flows out, consequently 

 they can never be used for histological work. 



CAUSAL ORGANISM. A filtrable virus seems to be responsible for the death of 

 these caterpillars. It is filtered with difficulty, however Bacteria are not respon- 

 sible for this disease. Minute dancing granules are observed in the Berkefeld 

 filtrate, which may be etiologically significant. No bacteria or polyhedral bodies are 

 observed in the filtrate. 



* Glaser, R. W. and Chapman, J. W. The Wilt Disease of the Gipsy Moth Caterpillar. 

 Jour. Econ. Entomol., 6, 1913, PP- 479-488. 



Reiff, W. The Wilt Disease, or Flacherie, of the Gypsy Moth, 1911. 



