The mother plant-lice, after producing a full 
generation of young aphides, become smaller and 
flatter than before, and, in probably all instances, 
very soon die. Some species—perhaps nearly all 
the species—of aphides pass the winter only or 
chiefly in the egg-state, all the perfect insects 
dying about the commencement of winter, and 
the progeny of the next year being hatched by 
the heat of spring. Yet just as female wasps and 
_ female humble bees, after having paired in au- 
tumn, and survived all the males, find shelter 
during winter, and remain ready to bring forth a 
| numerous progeny in spring, so many of the per- 
_ fect aphides pass the winter in sheltered places, 
_ and find all the scanty nourishment which they 
_ require either from the perennial portions of their 
own proper plants, or from plants of similar char- 
acter or juices to their own. In Sweden, where 
_ the cold of winter is much more severe than in 
England, the Aphis pini lives through the win- 
_ ter on the branches of pines; and both in Eng- 
land and on the continent, females of the several 
species which feed on ligneous plants may, by any 
careful and minute observer, be seen, in the very 
_ middle of winter, in the chinks or cracks of the 
| branches of trees. 
“Towards the end of Decem- 
ber and the beginning of January,” says Reaumur, 
““T have seen several plant-lice on the buds of 
young shoots on a peach-tree, after some days of 
severe frost. These were wingless females, very 
plump, and full of young.” Even species whose 
normal plants are herbaceous and either annual 
in cultivation or perennial only in the roots, seem 
to have little difficulty in temporarily accommo- 
dating themselves even in summer upon other 
plants, or in finding during winter all the scanty 
nourishment which they require. Several species 
of our native plant-lice may almost constantly, 
both in summer and in winter, be seen infesting 
the tender exotic plants of our rooms and our 
green-houses. The bean dolphin, even when 
plenty of fresh bean plants are in the immediate 
vicinity, may be occasionally seen spread overabed 
| of spinage or dispersed among plants of the goose- 
foot family ; the cabbage aphis may often be seen 
upon mustard plants, and sometimes upon rad- 
ishes ; and the rose aphis may occasionally be ob- 
served upon lavateras, chrysanthemums, and 
pelargoniums. All attempts to combat or exter- 
minate aphides, therefore, ought to be conducted 
on the assumption that fertile females may be 
found in considerably different situations from 
their normal ones, and may even retain their 
vitality and be maturing their fecundity during 
winter. | 
Some entire species-of aphides, and certain por- 
tions or generations of other species, appear to be 
migratory. All the individuals of the Aphis hu- 
mult, though sufficiently numerous to cover the 
leaves of the hop plantations in millions, have 
been observed, for several successive years, to dis- 
appear soon after mid-summer. The bean dol- 
phin, the zebra plant-louse, and some other spe- 
APHIS. 
cies, are also seen to make a total disappearance 
at some period in summer ; and though they may 
in some instances die on or near the place where 
they disappear, yet, in the majority of instances, 
they obviously migrate either to other districts 
to obtain supplies of food, or to the sea-coast to 
be drowned and washed away in the same man- 
ner as the locusts of oriental countries. “I once,” 
says a naturalist, “ witnessed, to my great annoy- 
ance, an emigration of aphides, when travelling 
in the Isle of Ely. The air was so full of them 
that they were incessantly flying into my eyes, 
nostrils, &c., and my clothes were covered by 
them; and in 1814, in the autumn, the aphides 
were so abundant for a few days in the vicinity 
of Ipswich, as to be noted with surprise by the 
most incurious observer.” The provision made 
by the Creator in their organism and economy, 
for enabling them to migrate, and for regulating 
the time and the extent of their migrations, has 
the same wonderful character as the laws of their 
reproduction. In spring, all the aphides which 
appear are wingless females; as the season ad- 
vances, some winged females appear and remove 
to a distance; in the new quarters of the winged | 
females, most of the next generation are wingless 
females ; and in autumn, at the appearance of the 
last generation of the season, most of the males 
are wingless to retain them with the main body 
of the females on the spot, and a few are winged 
to enable them to migrate to distant colonies. 
The winged insects, both male and female, pair 
with the wingless ones; and all the young which 
are destined to become winged have the elements 
of the wings folded up in little bunches at the 
shoulders, and are not practically winged till 
after the third or fourth casting of the skin. 
The devastations of the aphides are effected by 
means of their haustellum, variously styled in 
popular language their beak, their sucker, and | 
their mouth-sucker. The haustellum of the Aphis 
quercus—which, on account of the comparative 
largeness of the species, may be advantageously | 
selected to illustrate the haustellum of the whole 
tribe—is much longer than the body, and, when 
unemployed, is carried in such a manner between 
the legs, close to the belly, as to project behind, 
and look like a slightly upward curved tail. See 
Fig. 5 and 6, Plate X VJ. It terminates in so mi- 
nutea hole, that Reaumur could not observe it with 
his most powerful microscopes, and proved its 
existence only by pressing out from it a drop of 
fluid. Two instruments of a brownish colour 
have been observed within the tube, and were 
conjectured by Reaumur to act like the piston of 
a pump. The insects, when forcing the sucker 
into the bark of a plant, press down their head 
and elevate the hinder part of the body, and, in 
consequence, exert considerably more power than 
if they were to maintain a horizontal attitude ; 
and, after they have pierced a hole, they continue 
at it night and day, without any locomotion, so 
long as they can obtain through it a sufficient 
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