126 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



beetles feed for a time on the inner bark around their pupal 

 beds and then issue forth by small exit holes. 



This description refers to typical unconfused galleries, but it 

 is impossible in most cases to trace either mother or larval 

 galleries when the outer bark is removed. It is usual to find 

 all the inner layers of bark converted to dust. 



It would appear that many factors influence the period of the 

 life-cycle from egg to adult. This time varies according to the 

 season of the year, the quality of the food material, and the 

 degree of shade or sunshine to which it is exposed. In one 

 case, from eggs laid in May the larval state extended over June, 

 July, and into August; pupation was during parts of August 

 and September, and perfect beetles emerged during the latter 

 month. These lived over winter, and practically the same 

 cycle was produced in the next year. Under the same condi- 

 tions, however, eggs laid in June might produce larvae which live 

 as such till the following June. The perfect beetles then emerge 

 in July. In the typical life-cycle it would appear that the larval 

 period is from 69 to 7 1 days, but when the larval stage is carried 

 over the winter it may extend to n^ months or longer. 



Investigations into the number of broods that may be expected 

 in a year are rendered difficult by the fact that, after the first 

 egg-laying the parents do not always die, but may feed for a 

 period and again proceed to pairing and egg-laying. Making 

 deductions from repeated observations, the investigator has 

 come to the conclusion that "even under the most favourable 

 circumstances the occurrence of a double generation in the 

 succession of parents, children, and grand-children within a single 

 year is most unlikely." Similarly, microscopic examination of 

 the reproductive organs of females that had completed egg-laying 

 in June, and had remained feeding under the bark till November 

 of the same year, showed that these were not yet ready for 

 egg-laying. 



Cryphalus abietis has been found on the Continent mainly as 

 a spruce-attacking species, although it is also known to be an 

 enemy of Abies and Pinus. Of the genus Pinus it is said to prefer 

 Pinus strobus. In Scotland it is recorded on various species of 

 Abies, as well as Picea excelsa and Pseudotsuga Douglasii. 



The favourite breeding-place is in dead and sickly trees, twigs 

 and branches of all ages. It is said to prefer material not 

 exposed to the sun. Heaps of brushwood are common places 



