156 



P. pyri, L., also occurs in Sweden, but is probably very rare. Hiber- 

 nation takes place in the adult stage ; the eggs are deposited in spring. 

 Owing to the scarcity of this species, injury by it does not appear to 

 have been observed. 



Up to the present P. pyricola, Forst., has not been observed in 

 Sweden. 



EscHERiCH (K.). Die Generation des grossen braunen Russelkafers 



{Hylohius ahictis). Zugleich eine Bitte um Mitarbeit. [The 

 Life-history of H. abietis. Also a Request for Co-operation.] — ■ 

 Forstwissenschaftliches Centralblatt, [sine loco] 1920, no. 12, pp. 

 425-431. 



A full knowledge of the life-cycle of Hylohius abietis has not yet 

 been obtained. Opinion is divided as to whether the larvae pupate 

 immediately on reaching maturity or require a long larval rest period 

 in order to become capable of pupating. Furthermore, it is not clear 

 whether the young adults are capable of reproduction immediately 

 after emergence or require a preliminary long maturing period during 

 which they feed. 



Acceptance of the first alternative in both the above cases involves 

 the assumption of a short hfe-cycle (one year or less), and acceptance 

 of the second of a life-cycle lasting about two years. 



The belief in a two-year cycle is held by Ratzeburg and others. 

 The author is in agreement with them, as a result of experiments 

 made in 1915-1916 with breeding-logs in two districts of Bavaria 

 differing rather markedly from one another. The following data were 

 secured in both places : — Chief oviposition, from April to June 1915 ; 

 chief growth-period of the larvae, ended by the end of September 

 1915 ; larval rest period, from October 1915 to June-July 1916 ; 

 pupation, from July to mid-August 1916 ; and emergence of the 

 young adults, after a 2-3 week pupal stage, from mid-August to 

 September 1916. 



The variations noticed in the size of the larvae in the summer of 

 1915 were compensated for in the next year, so that all the adults 

 emerged together. On 5th September 1916 none of the logs harboured 

 any larvae or adults. 



Some of the young adults were caged in pairs ; they fed on the 

 branches given to them but did not mate. It is therefore clear that 

 a period of 15 months was required from egg to adult, and that if the 

 fact that pairing did not take place in autumn be accepted, a two-year 

 cycle obtains. 



As others have made similar observations, there is no doubt that 

 H. abietis is able to undergo a two-year cycle. 



On the other hand, there exist actual observations of a much shorter 

 life-cycle. In his cage experiments von Oppen found the period from 

 egg to adult to be about 12 months. It is true that the beetles did 

 not attain the full average size, so that Altum spoke of maturity due 

 to necessity. Rothe (1910) observed that in localities where clearing 

 had been done, development was still shorter in Hylobius in the small 

 remainder of roots left in the ground. He also ascribed the early 

 emergence to pupation owing to lack of food. Another short cycle (3-4 

 months) was observed in Alsace by Eichhoff (1882), who was thus 

 led to suppose the occurrence of two annual generations. 



