HO ME. E. P. STEBBIXG ON THE LIFE-HISTOKY OF 



black. These hirsute white patches appear on the head, upon each division of the 

 thorax, and two little tufts, set side by side on each segment, run medianly down 

 the dorsal surface of the abdomen. On the prothorax these white setae are in a 

 transverse ridge ; on the rneso- and metathorax they are in two large patches as on the 

 abdomen. The wiugs become a paler green or yellow, the costal and median nervures 

 being strongly marked and orange in colour, the transverse intersecting ones being 

 silvery (fig. 7). 



The insect by now, i. e. within three hours of its last moult, has lost all its brilliant 

 colouring and has- become dull and inconspicuous. It only differs from the winged 

 form to be found at this period on the needles of the Silver Fir by being colourless, but 

 iridescent in certain lights. 



A certain proportion of this winged generation, which consists of females only, from 

 the Spruce galls fly off to the Silver Fir, where I have found them in the first half of 

 July clinging to the new year's needles. The others remain on the needles of the 

 Spruce They bury their proboscides in the tissue of tiie under side of the leaf, taking 

 up a position parallel to the long axis of the leaf with head pointing downwards. 



Summary. 



We may summarise this portion of the life-history as follows : — 



In the early spring the stem-mother lays a mass of eggs just beneath a bud on a 

 branch of the Spruce in the spot where she has hibernated through the winter with her 

 long proboscis fixed in the cambium layer of the branch. The irritation set up by the 

 sucking of the female has already resulted in the first beginnings of a gall the swelling 

 of which, commencing on the stem, subsequently envelops the whole of the developing 

 spring needles of the bud. The larvae hatching out from the eggs at the commence- 

 ment of May get enclosed in this gall. The growth of the gall and the larvae continues 

 throughout May and June, the gall becoming mature or " ripe " and the larvae fully 

 grown about the first week to middle of July. The gall differs from the European one 

 in that the whole of the needles become absorbed within it, only a minute portion of 

 the tip protruding from the hexagonal cap or lid forming the cover to each compartment 

 of the gall. The larvae moult their skins several times during their growth in the 

 chambers of the gall. In July the lower edges of the caps or lids of the galls open, 

 the cap drying and shrinking, and the larvae crawl out of the chambers on to the outside 

 of the gall. Here they at once cast their skins, the little flies crawling out. At this 

 moment the flies are highly coloured little insects, the wings being rolled up into little 

 bundles on the thorax; these rapidly unfurl, straighten out and stiffen in the sun's 

 rays, and become functional. Some of this winged generation, which consists of females 

 only, remain on the Spruce and lay eggs there; the rest fly to the Silver Fir and 

 oviposit on the needles or twigs. These eggs, or a portion of them, hatch out within 

 a week or fortnight, and give rise to a generation of larvae which crawl on to the 

 branches which have developed a first thin brownish-yellow cortex and bury their very 

 long proboscides deep down through a crevice of the bark into the cambium below. The 



