149 



violacea, L., was never found breeding in trunks used for traps ; its 

 larval mines occur in 3-6 year old twigs in the upper portion of pine 

 crowns, the pupal chambers being at the surface. This marked 

 specialisation of M. violacea results in its seldom playing a dangerous 

 part, owing to its breeding opportunities being so limited. Whereas 

 an attack by P. pini involves the presence of unhealthy trees, that of 

 M. violacea depends on the presence of tops and branches that have 

 been left on the ground. The only instance of an extensive infestation 

 by M. violacea was seen in a thinned stand of Finns montana, all the 

 branches on the ground being infested. Pityogenes hidentatus, Hbst., 

 and Pogonochaerus fasciculatiis, DeG., also depend on the presence of 

 -clearings where tops and branches are l\ang near to the growing 

 trees. 



Cidaria dilutata, Thnbg., is a periodic pest in the birch zone of the 

 Scandinavian mountains. In 1918 it appeared in eight Swedish 

 districts This periodicity can only be explained by assuming that 

 in these districts certain checks on the moth had been removed. 

 Such checks are represented by an ant, Formica rufa, and by parasites, 

 of which Rhogas circiimscriptiis, Nees, and Itoplectis aliernans, Grav., 

 var. kolthofi, Auriv., were bred by the author from larvae of Cidaria. 

 They are distinctly polyphagous and should therefore be numerous 

 in regions where many hosts occur. If, however, C. dilutata is the 

 only host in the Scandinavian birch zone, the parasites must be few 

 in number, and therefore unable to check an outbreak of this moth 

 at its outset. The absence of F. rufa and of alternative hosts of the 

 parasites of C. dilutata probably accounts for the outbreaks of the 

 latter. A warm spring and a warm autumn appear to be contributory 

 factors. Gelis alternans, Thnbg., var. petulans, Forst., and G. instabilis, 

 Forst., were also bred, but are certainly hyperparasites. 



Spessivtseff (P.). Bidrag till Kannedomen om Splintborrarnas 

 Naringsgnag. [A Contribution to the Knowledge of Feeding 

 by the young Adults of European Scolytids.] — Medd. Stat. Skogs- 

 forsoksanst., Stockholm, xviii, no. 6-9, 1921, pp. 315-326, 5 figs. 

 (With a Summary in German.) 



The feeding done by young adult Scolj'tid beetles is either ignored 

 ■or little recognised in European text-books. It is only lately that 

 notes on the subject have appeared. Wichmann has observed this 

 phenomenon in Scolytus {Eccoptogaster) laevis, S. {E.) pruni and 

 S. (£".) pygmaeus, and Gornostaev believes that the rosette-like 

 mines of young S. nigtdosus are due to this cause. 



In 1921 the author was able to confirm Wichmann's observations 

 on S. laevis. On emerging from the deep-lying pupal chamber the 

 young beetles come out of the wood, resembling in this respect Myelo- 

 philus minor and Hylesinus fraxini. The young individuals of 

 S. laevis are, however, externally similar to older ones. The duration 

 of feeding by the young beetles is short, lasting four or five days only 

 in warm, sunny weather. The manner in which this is done varies 

 considerably. Usually it is the green shoots that are attacked, a mine 

 about f cm. long being bored inside them. Sometimes even the leaf- 

 stalks are destroyed, and thicker twigs may also be attacked in the 

 5ame way. These injuries resemble those found in hickory and due 

 to 5. quadrispinosus in America. The femfile genitalia are not mature 



