FAMILY SCOLYTIDAE 



523 



The beetles of the Hrst j^eneration of the }ear issue earl\- in Ma\', and 



tunnel into trees to oviposit. The beetle is usually or 



Life History. often found in company with Tomicus ribbcntropi (p. 552) 



in the trees. It appears to come in a little later than the 



larjj^er beetle, and it is possible that it seeks out trees already attacked 



by it. The insect remains in the trees longer than the Tomicus, and will 



attack trees whose bark has lost the freshness the latter requires. It thus 



resembles in habits Polygrdphus nigra, though it differs in appearance, 



size, and abundance from that insect. P. pini infests the bole of the tree 



and is only rarely found in the tops and branches in company with 



Polygraphiis major. 



It is probable that this insect has three to four generations in the \'ear 

 in favourable seasons, the first flight of beetles, from the eggs laid at the 

 beginning of May or late in April, appearing towards the end of May (I have 

 found pupae and lightish-brown immature beetles in the galleries on 

 22 Ma}). These at once lay eggs, and a second generation of beetles 

 appears about the beginning of July. Immature beetles were found on 



22 June at about the same elevation 

 as those found on 22 Ma}-. A third 

 brood of beetles from eggs laid by 

 these latter makes its appearance at 

 the end of September and beginning 

 of October, and at once lays eggs. 

 These latter develop into larvae, 

 some of which may reach the 

 beetle stage and ihus pass through 

 the winter. It would appear, how- 

 ever, that a large number pass the 

 cold weather as larvae enveloped 

 in a thin, white, papery cocoon at 

 the end of their larval galleries, 

 which they slightly enlarge. In 

 April these probably turn into pupae, 

 the resulting beetles emerging from 

 the tree towards the end of the 

 month or some time early in Ma}'. 

 Fio. 338.— I'airing-chamber (/) and eg^- The number of generations in 



galleries (e') of Polyi^raphits pint, Steb., in a year and the time spent in each 



blue pine. North-West Himalaya. (E. P. S.) i-r 1 • r ^u i j j 



^ . \ ^ liie-cycle require further study and 



corroboration, as there is not improbably a certain amount of overlapping. 



The 6 bores into the bast through the bark of the tree and excavates in 

 it a pairing-chamber, being joined there by the ?. At present my observa- 

 tions have shown me that there are always two beetles to be found in this 

 chamber whilst it is under construction. After pairing has taken place 

 the ? bores an egg-gallery away from the chamber in the bast and lays her 



