CHERMES HIMALATENSIS ON THE SPRUCE AND SILVER EIR. 109 



may open anywhere all over it. The portions more exposed to the sun and in direct 

 contact with warm air-currents ripen first. An examination of the insects within the 

 galls, just hefore the latter begin to open, will show them to be little thickish, puffy, 

 wingless Aphids, dull purple in colour and much ridged dorsally, with greatly enlarged 

 globose anterior coxae (PI. 21. fig. 2). This is the last stage of development of the 

 insect within the gall, no functional alar appendages being present. 



A section cut across the gall at this stage shows from 5 to 7 chambers of considerable 

 size (fig. 3), each containing on the average eight purple grubs amidst a mass of fine 

 white cottony material and cast larval skins. 



In opening, the upper two edges or sides of the diamond-shaped outer covering of 

 the chamber become detached at their points of juncture with the two lower sides 

 of the cover of the chamber next above, thus forming a kind of lip purplish in colour, 

 which can be forced open with a forceps. The external surfaces of the diamond- 

 shaped coverings then contract slightly, thus causing the aperture to permanently gape, 

 the opening becoming wider and wider as the surface dries and consequently contracts 

 (figs. 1, 4). The slit is at first quite narrow, but as soon as it appears the insects 

 commence to crawl out. On reaching the outside of the false cone the fat purple 

 nymph (fig. 2) at once undergoes its last moult. In doing this, the skin splits down a 

 median line, both dorsally and ventrally, as far as the mesothorax dorsally, and the first 

 and second pair of coxae ventrally ; the insect then slowly crawls out, leaving the white 

 papery cast skin, to which are attached the dark-coloured leg and antenna cases, 

 behind it. 



After this last moult it will be seen that the Chermes has undergone a great change. 



It now appears as a small gorgeously coloured Aphid. On either side of the thorax 

 two little bright-coloured bundles are visible, a bright Naples yellow anteriorly and 

 vivid apple-green posteriorly (fig. 5). The whole insect, in fact, is very highly coloured 

 and looks at this stage as if it had just been freshly painted with the very brightest tints 

 in Nature's colour-box and then given a coating of varnish. As soon as the Chermes 

 has freed itself from the last attachment of its last skin it begins to crawl actively 

 about on the exterior surface of the gall, and the little yellow and green bundles unfold 

 and disclose the fact that they are the rolled-up alar appendages (cf. fig. 5). As far as 

 I could perceive, the insects themselves take no active part in unfolding these wings. 

 They do not hang themselves up to get them unrolled, as is the case with Lepidoptera, 

 but simply walk about, and under the influence of the sun and heat the wings rapidly 

 spread out, stiffen, and become functional. I noted that in many cases, even before the 

 insect has entirely freed itself from the last larval skin, the little bundles had so far 

 unrolled as to he quite distinct from one another. Within half an hour from the time 

 of leaving the cone, the wings are fully unrolled, being held at an angle on the side of, 

 but not meeting in a roof-shaped manner over, the abdomen. These wings are pale 

 apple-green in colour with yellow nervures except at their juncture with the thorax, 

 where they are chrome-yellow (aide fig. 6). 



Within one and a half hours of shedding the last skin, patches of white setae begin to 

 appear upon the Aphid, and the meso- and metathorax turn from orange to shining 



16* 



