88 Second Report on Economic Zoology. 



No male is known to occur, and yet we get successive generations 

 not only going on through the summer, but the asexual reproduction 

 carried on from year to year. The Larch 

 Bug or Aphis {Chermes laricis) (Figs. 17, 18) 

 is thus agamic ; but it is now thought that 

 this larch pest is only a form of another 

 species, the Spruce Gall Aphis (Chermes 

 ((Metis). These two previously supposed 

 distinct species are, I feel sure, one and the 

 same — merely different forms which can 

 migrate between two food-plants ; certain 

 stages being passed on the spruce, other 

 The true sexual form is the Spruce Gall Aphis 

 This form, so well known on account of 



Fig. 18. — Chermes laricis 

 (winged female). X 20. 



stages on the larch. 

 {Chermes uhietis) (Fig. 19) 

 the beautiful pineapple -shaped galls (Fig. 19, «) they produce, attacks 

 the spruce only. It occurs on the White Spruce (Picca alba), the 

 Norway Spruce {P. excel sa,), the Blue Spruce (P. 'pungens), the Black 

 Spruce {P. 7ii(/ra), and the Hemlock Spruce (P. canadensis). They 

 are first noticed on the spruce as small, oval, wingless, ochreous 

 yellow lice ; the apterous viviparous females. These creatures (b) 

 have passed the winter hidden under some bud scale or bark crevice, 

 like the laricis form. They soon settle down near the base of a 

 young leaf, and shortly small swellings appear, within which they 

 encircle themselves. These females lay masses of eggs (Fig. 19, d) 

 which soon hatch into lice. The lice at once puncture the twig and 

 cause it to swell ; at the same time the needles also swell, especially 

 their bases, and so the curious fir-cone, or pineapple-like gall, grows. 

 As the swollen needles unite at their bases, there are formed 

 chambers in which the lice live and grow and by their constant 

 irritation increase their size until each chamber may hold as many 

 as fifty larvae. Each chamber is lined with a dense mealy substance 

 and also contains numerous opaque or semi-opaque globules, often 

 coated with tlie meal. The cones are at first pale green and pink, 

 but as they grow they become brown and often an inch in length ; 

 each may contain as many as two thousand inhabitants. From the 

 middle of June into July the scales of the gall split, each having a 

 little semicircular opening ; previous to this taking place the larva; 

 have entered the pu]ial stage, the pupa (Fig. 19, /) being reddish- 

 brown with a slight mealy coating, with green wing-cases and 

 thoracic markings. Like the laricis they vary in colour, some being 

 pale slaty-grey, others pinkish. From early June to July these 

 pupse hatch into the winged females, which crawl out of the galls, if 



