336 The Large Poplar Lone/horn 



cotton cage. This female lived until August 28th, 1918. In other cages 

 similar observations were made, only the beetles lived somewhat longer. 

 In some cases the females lived for three weeks after egg-laying was 

 completed, while the males lived for one week after pairing. 



During the period of egg-laying freshly cut pieces of stems of poplar 

 were placed in all the cages so that plenty stem-surface would be given 

 for the females to lay on. The eggs laid on the stems enclosed in the 

 cages were examined at intervals to ascertain if any of them had hatched, 

 but in no cases, even in those eggs laid as early as August 2nd, 1918, had 

 larvae issued. Dissection of some of the eggs at the end of September, 

 1918, yielded young larvae. 



Throughout the hibernating period, October, 1918, to May, 1919, the 

 eggs on the stems were examined at intervals but always without any 

 hatching. On examination of the stems on June 14th, 1919, however, 

 some of the eggs present on the stems had hatched. Others hatched in 

 the following days and by June 20th, 1919, all the eggs present on the 

 stems under my notice had hatched. The egg stage in these experimental 

 cases thus lasted about ten and a half months. 



On the stems marked in July, 1916, left in the open under natural 

 conditions, similar results were obtained as regards the length of both the 

 larval and the pupal periods. Adults were found to escape from stems 

 in the open — marked and unmarked — from July 16th onwards, and 

 egg-laying was found to take place on the basal portions of the stems 

 from August 4th, 1918, to August 25th, 1918. The principal period of 

 emergence of the beetles was from mid July to mid August. During the 

 period of ovi position in the open, a search of the infested areas was made 

 for females that were laying eggs and also for fresh egg-bites. Where 

 these were found, nicks were cut so that the places could be detected 

 later. From August 4th, 1918, to August 25th, 1918, a large number of 

 those egg-notches were marked. The marked stems were examined every 

 three days throughout the late summer and autumn, but in only two 

 cases were eggs found to have hatched. The date on which these w r ere 

 found was August 26th, so that the incubation period was in this case 

 about three weeks. In all the other cases examined the eggs remained 

 unhatched. Portions of these stems cut down in May, 1919, were kept 

 in the open and examined at intervals, but not till June 15th, 1919, did 

 any of the eggs on them hatch. The two cases where eggs hatched in 

 late August, 1918, were exceptional and large numbers of stems containing 

 eggs w r ere examined. 



During the summer of 1919 many egg-incisions were made by females 



