1(SG Bionomics of Oryphalus abietis 



In another experiment carried out in a similar method and under 

 similar conditions 60 adults were liberated on May 2nd, 1917. Dis- 

 sections of many mother galleries were made at intervals with a view to 

 collecting all the data possible on the making of the gallery and the 

 egg-laying. 



In one dissection made 16 days after the commencement of the 

 gallery I found one egg laid while in another four eggs were laid by the 

 end of a month. 



The incubation period of the eggs was on an average 10 days. Large 

 numbers of adults continued to escape from my "stock material" up 

 to June 15th, 1917. 



The time taken by the parent beetles to bore the mother gallery 

 varied from 5 to 7 weeks. 



Some larvae fed for 69 days and then pupated, the pupal period 

 lasting about 29 days. 



Thus in the case of eggs laid on June 4th, 1917, i.e. a month after 

 the commencement of the mother gallery, the total period until the 

 imago stage was reached on September 21st, 1917, was 108 days. 



In my control experiments in natural conditions, some badly 

 infested Silver Fir branches in the woods at Aboyne examined on June 

 26th, 1917, were found to contain hundreds of eggs of C. abietis and in 

 many cases the females had not yet completed their egg-laying. These 

 branches were examined at intervals throughout the summer and the 

 length of the various stages was found to be as follows, viz. egg on an 

 average 10 days: larva 71 days: pupa 22 da3's. That is to say the life- 

 cycle from the egg stage at the end of ,Iune to the adult stage on 

 September 27th was 93 days. 



While in the above cases many individuals of the same brood reached 

 the adult stage in the average period, quite a number of others were still 

 in the larval stage at the end of September, 1917, and hibernated as 

 larvae. 



As showing the variations found in the length of the life-cycle I have 

 set out in the following diagrams the life-cycles which I met with in my 

 control experiments and in the open. 



Diagram A. 



+ = adult. •=egg. -= larva. 0=pupa. 



Year Jan. Feb. March Apl. May June July Aug. Sep. Oct. Nov. Dec. 



19I() -t • -O 0+ + + + 



1917 + + + + ^- , , _ _ _ Q o+ 



