W. RlTCHIK 



195 



In Table No. 1, 1 have .summarised my observations and results of 

 the control experiments already referred to under the paragraph dealing 

 with the length of a life-cycle in a single generation. From this table it 

 will be seen that the new generation developed from eggs laid in May 

 of the year and issuing in September is unable to proceed to an egg- 

 laying, i.e. a new generation, in the same year. At the earliest it would be 

 the next spring before they laid eggs. Similar results were also obtained 

 from experiments and dissections from material bred in the open in the 

 summer and autumn of the vear 1917. 



Table I. 



Even adults derived from overwintering larvae and which issue in 

 midsummer do not have a new generation in this year as is proved by 

 the undernoted observations. 



Some larvae that hibernated during the winter of 1916-17, the first 

 of which pupated on June 5th, 1917, issued as adults from July 21st, 

 1917, to August 20th, 1917. The majority of these young adults however 

 never swarmed at all during the year 1917 but remained underneath 

 the bark where they were reared and hibernated the second winter as 

 immature adults. That they were immature was proved from a large 

 series of dissections made of their reproductive organs in November and 

 December, 1917. 



Some of the reproductive organs of those adults that did swarm in 

 July and August of 1917 were also examined as the beetles issued from 

 the material where they had been reared but they too were found to be 

 immature. The others that issued I liberated on August 14th, 1917, in 

 muslin cages enclosed within which were paraffined branches of Silver Fir, 

 on which they could feed or breed as they chose. On the 16th of August, 

 1917, a number of them were found to be boring on the Silver Fir branches, 

 evidently feeding. Examination of these branches was made at intervals 

 up to Dec. 3rd, 1917, but in no case were eggs found in any of their 



