17 



season was taken into consideration. For instance, in locali- 

 ties which had prevailing east winds the infected material 

 was exposed near the eastern border of the forest, but still 

 inside of it, so that the wind, before reaching the larger part 

 of the wood, was forced to strike first the center of the diseased 

 area. It may be mentioned that in some cases, where no con- 

 venient cloth was at hand, the breeding cages themselves with 

 the material, after the removal of the cover, were hung between 

 limbs. No difference was observed in the results. The in- 

 fected material was planted in most of the localities at a time 

 when most of the caterpillars in the field were undergoing the 



Fig. 1. Method of hanging hammock in tree. 



third molt. The respective ages of the caterpillars will be 

 mentioned under each experiment. 1 



It was important to select places which gave the best guaran- 

 tee for the health of the growing caterpillars; hence, special 

 attention is called to the fact that in the experimental localities 

 no disease is known to have occurred among the caterpillars 

 of previous years. 



1 I had always planned to plant the disease as soon as it made its appearance in one or the other 

 of the broods. This was, however, frustrated on several occasions by various circumstances. 

 For instance, some local superintendents did not notice the Flacherie till after the disease had 

 prevailed for several days. It was, further, not always possible for me to depart immediately 

 upon receiving a communication concerning the outbreak of the disease. It was also almost 

 impossible for one man to transplant the infected material to all the chosen places during the 

 short time in which the gypsy moth caterpillars were in the third or beginning of the fourth stage. 

 This is the reason why in some localities the disease was planted later, although the caterpillars 

 were already beyond the third molt. 



