May 15, 1915 



Wilt of Gipsy-Moth Caterpillars 



123 



SERIES 3 



Last-Stage caterpillars were used in the third series of experiments, 

 which was begun on July 14. These animals were obtained from a locality 

 in which a tachinid, Compsilura concinnata, abounded. Later, during 

 the course of the experiments, quite a large num- 

 ber of these caterpillars succumbed to parasitism 

 by this species. 



The wilted material was strained through cheese- 

 cloth to equal 50 c. c. This was diluted with ten 

 times its volume of sterile water and filtered 

 through a paper filter. This filtrate was again 

 diluted ten times and a portion was used without 

 further treatment while the rest was passed through 

 Berkefeld candles. 



Figure 14 represents the mortality among 40 

 caterpillars fed with the Berkefeld filtrate. Eight 

 caterpillars died of wilt, seven of the "other cause," 



twenty succumbed to 

 tachinid parasitism, and 

 five male moths emerged. 

 Figure 1 5 gives the mor- 

 tality among 40 caterpillars fed with unfiltered 

 material. Fifteen died of the wilt, four died 

 of the "other cause," one escaped, eleven 

 succumbed to tachinid parasitism, and nine 

 male moths emerged. 



Figure 1 6 shows the deaths among 20 control 

 ^ , . , insects. Onediedof wilt, nine died of the "other 



Fig. II. — Curve showing the mor- • • i 



taUty among 50 gipsy-moth cat- causc," ouc succumbcd to tachmid parasitism, 

 erpiiiarsfedwith wilt virus after ^j^^j . j^^le and A. female moths emerged. 



filtration through the Berkefeld . . . .,_^,,__- 



filter. The mortality for senes 3 is given in table 1 v . 



Fig. 10. — Curve showing the 

 mortality among 19 " con- 

 trol" fifth-stage gipsy- 

 moth caterpillars. 



Table IV. — Mortality among gipsy-moth caterpillars in laboratory experiments (series j) 



a I escaped. 



Again, the number of caterpillars which died after feeding on the 

 unfiltered material was almost twice as great as the number that died 

 after feeding on the Berkefeld filtrate. 



