102 ME. B. P. STEBBING ON THE LIFE-HISTORY OE 



the bark of the stern of young saplings. The cottony masses contain a number of egg- 

 bunches, having the appearance under the lens of bunches of yellow and brown grapes, 

 as shown in PL 22. fig. 5. These eggs are those laid by the Colonici. From these 

 eggs hatch out in the early spring little larvae, which crawl on to the newly-developed 

 young Silver Fir needles, insert their proboscides into the tissue of the under surface 

 and suck out the sap. These larvae reach full growth as apterous females, Exstjles 

 (fig. 2), in about three weeks, and these apterous females secrete cottony filaments, 

 under which they lay bunches of eggs on the needles, similar in appearance to the 

 spring ones, and die (figs. 3, 1). A portion of this generation is winged (fig. 7) and 

 would seem to represent a part of Burdon's Generation IV. Sexupar^e. From the 

 eggs laid on the Silver Fir needles hatch out in a few days small red grubs (see fig. 8), 

 which in their turn become full-grown and lay similar eggs (Exsules). A portion of 

 these latter generations collect and feed down at the base of the needles and stem, 

 and cause the needles to contort and twist and curl inwards, forming a corkscrew 

 termination to the shoot towards the end of June {of. PI. 23. fig. 1). This corkscrew 

 would almost seem to be of the nature of a rudimentary gall structure, and thus this 

 species differs fundamentally from the European Ghermes on the Larch, which forms 

 nothing in the shape of a gall-like structure. In this corkscrew both apterous (Exsules) 

 and winged (SEXUPARiE) insects are to be found. In the latter part of June and first 

 part of July the twisted-up needles are found to contain numerous eggs covered by the 

 usual dead mother skin and white cottony substance. These egg-masses are also to be 

 found on the twigs and stem of the tree and are very visible. 



These eggs hatch out into grubs, which grow into minute apterous female insects 

 furnished with very long proboscides (PL 23. fig. 3). These insects, if not already there, 

 crawl down on to the bark of the branch, insert their proboscides down a crevice into the 

 bast and remain feeding there (cf. PL 23. figs. 2, 3) throughout the rains, and, I think, 

 probably through a part of the winter, when they secrete the cottony material, lay eggs, 

 and die. 



The winged forms (Sexupar^e), or a portion of them, migrate to the Spruce, as I have 

 found living specimens on the old needles of the tree, as also dead insects stuck to the 

 needles. These insects presumably lay eggs upon the needles and give rise to the fifth 

 generation, the Sextjales. I have not found this generation on the Spruce. It would 

 presumably consist of wingless males and females, and give rise to the first generation, 

 the Ftjndatrices. 



From what has been said, it thus becomes obvious that one important factor governs 

 the appearance and duration of the various generations passed through upon the Spruce 

 and Silver Fir, and that is the monsoon. The rains burst in the Outer Himalayan 

 Region we are considering early in July and bring to an end Generations I. and II. upon 

 the Spruce and Generation IV. on the Silver Fir. 



With this brief review of the various phases of the life-history we will now proceed 

 to consider in fuller detail the life-stages passed respectively on the Spruce and 

 Silver Fir. 



