422 IVAR TRÄGÅRDH [22] 



SUMMARY. 

 Forest-entomological contributions II 1 . 



i. The sprnce resin fly {Chilosia morio Zett (?]). 



When lQoking for the flow of resin which signifies the presence of Den- 

 droctonus micans in spruce-trees one often finds other insects, f. i. larvae of 

 Tineida and Pyralidce, and often empty skins of some fly pupariwn are noticed 

 sticking in the resin. 



During the last years, however, mr. E. Lundberg, Kloten called my attention 

 to the occurrence of dipterous larvae in the resin, and subsequently the author 

 has found such larvae repeatedly in the same localities. I have not yet been 

 able to breed the larvae but dr. W. Baer of Tharandt, Germany, to whom 

 some specimens were sent has kindly informed me that they are identical 

 with the larvae which he found in similar localities and which he succeeded 

 in breeding, the imago being identified by the dipterologist A. Kuntze in 

 Dresden as Chilosia morio Zett. 



Remarkably enough, the larvae of this fly seems hitherto to have escaped 

 the notice of the European forest entomologists, with the exception of dr. Baer. 



In U. S. A., on the other hand, the larva of Chilosia alaskensis was re- 

 corded from similar localities by Burke already in 1905. In both cases it 

 seems to be an established fact that the larva is not predatory but takes its 

 nourishment from the sap of the spruce-tree. In Sweden, at all events, the 

 larva was almost ahvays found single, not associated with other insects. 



For the description of the larva the reader is referred to figs. 1 — 4. We 

 notice that the respiratory tube is divided into 3 parts which can be telescopically 

 extended and retracted. The top of the tube (fig. 4) has unusually great 

 circular plates and 4 pairs of well developed, fan-shaped bristles, bent for- 

 wards. The spirades are not visible from the surface but hidden underneath 

 the exteriör edge of the plates, which are surrounded by a high ridge. The 

 mouth hooks (fig. 3) are comparatively blunt, not very curved and on the 

 ventral side provided with a row of blunt teeth which are inserted in a deap 

 furrow. Their shape suggests that they are used as locomotory organs and 

 possible also as a kind of rasps. Certain observations made by mr. Lund- 

 berg and the author seem to suggest that the fly preferably oviposits in 

 wounds in the bark, because in the flow of resin caused when marking the 

 trees to be cut with an iron preparatory to thinning, the larvae occurred with 

 great frequency. It is also possible that holes made by Dendroctonus micans 

 but subsequently deserted may serve the fly for oviposition purposes. It is 

 not yet known, whether the injuries caused by the larva weaken the trees 

 and render them liable to be attacked by other insects. Probably this depends 

 on how many years the attack lasts and this Hme may vary but has in some 

 instances been found to extend över a couple of years. 



2. The one-banded pine ivecvil {Pissodes phhiiphilus Herbst). 



During the last years numerous observations have been made in Sweden 

 which show that P. piniphilus (fig. 7) is a common insect and that the in- 



1 No. I was published in Meddelanden från Statens Skogsförsöksanstalt H. 19, 1922. 



