554 William Reiff 



course, isolated the apparently healthy animals, but too many of 

 them had already contracted the disease. The first symptom of 

 flacherie appeared as a complete apathy, both in feeding and in 

 movement. Later the animals crept slowly up the walls of the 

 breeding cage and remained motionless under the lid, where they 

 died in the course of a couple of days. As a rule, one pair of pro- 

 legs was fastened to the gauze of the wall, while the anterior and 

 posterior portion of the caterpillar hung down on the right and left 

 side. The dead caterpillar at once decomposed, and often 

 dropped into several pieces at the least touch. 



The caterpillars were reared at out-of-door temperature. Pupa- 

 tion began the sixth of October. The time of pupation, that is, 

 the time which elapses between the attachment of the caterpillar 

 and the completed pupa, differs according to the prevailing tem- 

 perature. At 23° C. pupation took place in from 10 to 12 hours; 

 18° C. caused the caterpillars to pupate in 17 hours; 9° C. in about 

 48 hours; 6° C. in 60 hours, and below + 4° C. pupation did not 

 take place at all. The caterpillars, which I subjected for a long 

 time (up to 8 days) uninterruptedly to a lower temperature, vary- 

 ing between 0° and +3° C, died, no matter in what stage they 

 happened to be. I used for this purpose caterpillars of all ages: 

 animals that had not yet completed their second moult, up to those 

 which had all attached themselves for pupation. 



In the original locality Mr. Doll had found caterpillars of all 

 sizes as late as the end of October. Indeed, there were even 

 some freshly hatched butterflies, together with flown specimens 

 of the preceding generation. In his letter to me he suggested 

 the question as to whether the caterpillars might not hibernate, 

 since it was obviously impossible for the majority of them to pupate 

 during this same year, as the food-plant was mostly frozen and 

 the temperature was becoming lower from day to day. I am now 

 of the opinion, after the above experiments, that J. coenia never 

 passes' the winter in the northern states as a caterpillar, but that 

 all caterpillars die as soon as the temperature sinks to +3° C. 

 for several days. The pupa is not quite so sensitive to continued 

 cold as the caterpillar, but still to a considerable degree. All the 

 pupae which I exposed to a constant low temperature (—5° C. or 



