February, '16] CHAPMAN AND GLASER: WILT OF GIPSY MOTH 155 



were quickly discarded for fear that the infection might spread to the 

 remaining individuals. 



Animals needed for an experiment were taken from a particular 

 stock culture. The remaining individuals comprising this stock were 

 kept under close observation throughout the season i. e., the number 

 of deaths and the number of moths which emerged were recorded. 

 Thus in most cases, we were able to determine the health of a partic- 

 ular culture. Needless to say, no deaths in stock or experiment were 

 attributed to wilt unless all the gross and microscopic symptoms were 

 typical. (See Glaser, Journal of Agricultural Research, Vol. IV, No. 

 2, p. 104.) 



Simple and Passage Infections 



The following experiments were performed in order to prove whether 

 or not wilt is a true infectious disease. All caterpillars used for an 

 experiment were taken from a particular stock and isolated in sep- 

 arate, small, round tin boxes measuring three-fourths inches in depth 

 and two and one-half inches in diameter. Such tin boxes were found 

 far superior to the pasteboard boxes used during previous seasons. 

 By keeping the lid closed the proper humidity conditions are obtained 

 and the food remains fresh for two or three days if not eaten. The 

 caterpillars also moult regularly in these tin boxes and they seem not 

 to suffer in the least from their confinement. Lastly, the tin boxes 

 can be easily sterilized by boiling water and can be used over again 

 repeatedly. 



The stock animals were nearly all raised in glass fruit jars measuring 

 about three and one-half inches in height and in diameter. By screw- 

 ing on the tin tops, the proper humidity conditions could likewise be 

 obtained. If the humidity increased sufficiently so that drops of 

 water formed on the glass, a little dry sand put into the bottom of 

 each jar soon absorbed the excess moisture. 



Table VI gives the results of the first experiment. Twenty fifth 

 stage foreign clispar caterpillars were isolated, ten for the experiment 

 and ten for the controls. Caterpillars which died of wilt were ground 

 up in a motar with sufficient sterile water to facilitate the process. 

 This liquid was strained through cheesecloth and then diluted to 40 

 c.c. with sterile water. The solution was next filtered through paper 

 in a Buchner filter by using a slight suction. Ten caterpillars were 

 fed from an eye dropper (method of feeding described on page 152) 

 with the Buchner filtrate and ten controls, fed with the same filtrate 

 sterilized by autoclaving, accompanied the series. Eight caterpillars 

 died of typical wilt in the experiment and no controls succumbed. 

 Two controls died of an "other cause." Two moths in the experiments 

 and eight moths in the checks emerged. In the stock culture of 240 



