May 15, 1915 



Wilt of Gipsy-Moth Caterpillars 



121 



Fig. 6. — Curve show- 

 ing the mortality 

 among 15 control 

 second-stage and 

 third-stage gipsy- 

 moth caterpillars. 



Figure 7 represents the deaths among 26 fourth-stage caterpillars 

 obtained from Providence, R. I., in a lightly infested point which was 

 supposed to be entirely healthy. The disease had not appeared in the 

 field at the time the collection was made, and although 

 all were kept in one tray, not a single caterpillar died of 

 wilt in the laboratory. Twenty-five died of the "other 

 cause" and one male moth emerged. 



Figure 8 gives the mortaUty among 8 fourth-stage cater- 

 pillars obtained from Providence. Each caterpillar was 

 placed in a separate tray and the entire eight were starved 

 until they died. The post-mortem appearances were so 

 similar externally to the deaths from the "other cause" 

 that they are represented by a broken line. 



Figure 9 represents the deaths among 16 fifth-stage 

 gipsy-moth caterpillars kept in one tray. These were 

 from the same collection as those used in the experi- 

 ments. Not one case of wilt appeared, but they all died 

 of the "other cause." 



Figure 10 shows the deaths among 19 fifth-stage cater- 

 pillars, also from the same lot as those used in the ex- 

 periments. 



From figures 2 and 4 it is evident that the deaths from the wilt dis- 

 ease all occurred during days when the temperatures were high. Taking 

 the midway point between 79° and 80° F. in the tempera- 

 ture range 68° to 91°, it is found that 14 deaths occurred 

 at and above 80° against 9 deaths below that tempera- 

 ture. There seems to be no definite correlation between 

 temperature and the deaths from the "other cause." 



SERIES 2 



The second series of experiments was begun on July 3. 

 Last-stage caterpillars were used. Material strained 

 through cheesecloth with sterile water to equal 50 c. c. was 

 diluted with 20 times its volume of sterile water, then 

 shaken, and filtered through paper filters. A portion of 

 this filtrate was used as it was, part was filtered through 

 the Berkefeld candles, and another portion was sterilized 

 for the controls. The infections were repeated on July 6, 

 and another dose was administered on July 13 to all cater- 

 pillars that had not pupated. These experiments were 

 performed in a room some distance from the one in which 

 the first were carried on. 

 Figure 1 1 represents the mortality among 50 caterpillars fed with 

 the Berkefeld filtrate. Wilt caused the deaths of 13 in the cater- 

 pillar stage and of I in the pupal stage; 3 died of the "other cause"; 



Fig. 7. — Curve show- 

 ing the mortality 

 among 26 " con- 

 trol" fourth-stage 

 gipsy-moth cater- 

 pillars from Provi- 

 dence, R. T.. 



