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 ( Chernies 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 ( Chernies 
abietis). 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 
stages on the larch. The true sexual form is the Spruce Gall Aphis 
( Chermes abietis ) (Fig. 19). This form, so well known on account of 
the beautiful pineapple -shaped galls (Fig. 19, a) they produce, attacks 
the spruce only. It occurs on the White Spruce ( Picea alba), the 
Norway Spruce (P. excelsa), the Blue Spruce (P. yungens), the Black 
Spruce (P. nigra), 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 the 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 larvie 
have entered the pupal 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 
Fig. 18 . — Chermes laricis 
(winged female), x 20. 
