162 journal of economic entomology [vol. 9 



Summary 



(1) The chance method for obtaining healthy experimental material 

 is absolutely worthless on account of chronic carriers. 



(2) By selection a stock of caterpillars can be produced in which 

 spontaneous wilt mortality is reduced to a minimum. 



(3) Wilt is a true infectious disease. 



(4) The virus of wilt is filterable through Berkefeld "N" candles. 



(5) Caterpillars that have died from infection with the filtered virus 

 are flaccid, completely disintegrated, and full of polyhedra. i ^ 



(6) Microscopic examinations of the bottom sediment of centrifuged 

 Berkefeld filtrates and platings of such filtrates show that they are 

 sterile for bacteria. 



(7) Berkefeld filtrates are free from polyhedral bodies. 



(8) The nuclear inclusions called polyhedral bodies or polyhedra are 

 by-products of the disease. 



(9) We have been unable to force the wilt virus through Pasteur- 

 Chamberland "F" filters. 



(10) In our experiments the period from inoculation by feeding to 

 death varied from 13 to 29 days. The mean for simple infections is 

 20 days; for Berkefeld infections 23 days. The mean for all the experi- 

 ments is 21 days. 



(11) An accurate record of the stock cultures is necessary for the 

 interpretation of experimental results. 



(12) Wilt seems to be transmitted from one generation to another 

 through the egg. 



(13) Certain individuals among gipsy moth caterpillars seem to be 

 immune towards wilt. 



(14) A new disease appeared in our foreign stock. 



(15) A Saccromycete and a Micrococcus were isolated from cases 

 of this new disease. 



(16) The new disease appeared only during the later stages (fourth 

 and fifth) and differ clinically and microscopically from wilt. 



(17) Field observations have never revealed this new disease in our 

 American race. 



(18) Sacbrood and wilt are not identical. 



Literature Cited 



1. Chapman, J. W. and Glaser, R. W. 1915. A preliminary list of insects which 



have wilt, with a comparative study of their polyhedra. Jour. Econ. Ent., 

 V. 8, No. 1. 



2. EscHERiCH, K. and Miyajima, M. 1911. Studien iiber die Wipfelkrankheit 



der Nonne. In Natiirw. Ztschr. Forst-u. Landw., Jahrg. 9, Heft 9, p. 

 381-402, 6 fig. 



3. Glaser, R. W. and Chapman, J. W. 1913. The wilt disease of gipsy moth 



caterpillars. Jour. Econ. Ent., v. 6, No. 6. 



