55 6 FAMILY SCOLYTIDAE 



are made use of as " trap " trees and removed in due time, when the trees 

 arc full of mature grubs. Allowing girdled green trees to remain standing in 

 the forest is sure to lead to a bad infestation of this pest. 



Pompilus sp. The grub of this fly feeds parasitically upon the Tomicus 



larvae. 

 Parasitic and 



Predaceous Insects. Fty- The fly is black in colour, but I have not succeeded in 



obtaining any fully mature insects. Mr. Claude Morley identifies the 

 insect as a species of Pompilus. 



Grub. Yellow in colour, pointed at each end, legless, with a small head and seg- 

 mented body. 



Life History. I have taken this insect on several occasions in Jaunsar 

 (in 1902 and 1906), but usually in the larval or pupal stage. It should 

 prove comparatively easy to rear the flies, but I have been unfortunate 

 in my attempts. 



The life history is simple. The fly evidently creeps down the entrance- 

 tunnel of the Tomicus beetle and lays her egg or eggs in the pairing-chamber 

 or egg-galleries. The grub on hatching out crawls down the short gallery 

 in the bast of the young scolytid larva and attaches itself to the latter. It 

 then feeds parasitically on its host, but does not kill it until the Tomicus 

 grub has reached full size and completed its larval gallery and eaten out the 

 p>upal chamber at the end. The latter then dies of exhaustion, the greyish 

 black shrivelled skin being visible in the pupal chamber. By the time the 

 scolytid larva dies the parasitic grub has reached full size and pupates 

 in the pupal chamber made by its host. The flies mature about the time 

 the next generation of the Tomicus is egg-laying, and they then leave the 

 tree and oviposit in the egg-galleries of this generation of their host. 

 Observation would seem to show that the number of generations in the 

 year of the parasite coincides with those of its host. 



The Pompilus must be looked upon as a most important insect in the 

 forest. 



Cylistosoma dufali, Mars. (p. 106). This insect is predaceous upon this 

 Tomicus and also, doubtfully, on Polygraphus pini. 



Hcctle. Elongate, narrow, compact, black, and shining. The head is provided with 

 stout mandibles and angled brownish antennae ending in a club. Thorax wider than long, 

 smooth and shining. Elytra elongate, smooth and shining in centre, with several well- 

 marked longitudinal striae laterally ; the elytra leave the last two segments of the body 

 exposed, these segments being heavily punctured. Under-surface of body and legs brownish. 

 Length, ,/i, in. 



-This insect is to be found fairly commonly in the beetle 

 stage at the end of May at elevations of about 7,500 ft. in the coniferous 

 areas of the Xorth-West Himalaya. It frequents the galleries of the blue- 

 pine and spruce Tomicus, and apparently oviposits in them. The histerid 



