‘270 Plant-lice. INSECTS. Coccidas. 
over the kingdom ; so that a supply could not be 
obtained for the navju 
Plate 8, figs. 16 and 17, shows the Aphis rosm; the 
former figure represents the male, the latter the female 
of that species ; the figures, of course, are very highly 
magnified. 
Eriosoma. — This genus, so called by Leach from its 
seemingly woolly bod}-, has no tubercles at the end of 
the body for the secretion of honey-dew. The antennae 
are short and the fore wings have simple oblique dis- 
coidal nerves. 
To this genns belongs the Aphis lanata or A. lani- 
gera of authors, which is so destructive to the stems of 
apple trees. Mr. Knapp has given a most e.\cellent 
account of this insect* as observed in one of the western 
English counties. He says — “ Our apple trees here 
are greatly injured, and some annually destroyed, by 
the agency of what seems to be a very feeble insect. 
AVe call it, from habit or from unassigned cause, the 
‘American blight,’ this noxious creature being known 
in some orchards by the more significant name of ‘ white 
blight.’ In the spring of the year a slight hoariness is 
observed upon the branches of certain species of our 
orchard fruit. As the season advances this hoariness 
increases ; it becomes cottony, and towards the middle 
or the end of summer the under sides of some of the 
branches are invested with a thick, down}' substance, 
so long as at times to be sensibly agitated by the air. 
This substance on close examination is found to conceal 
a great number of small wingless creatures, busily 
engaged in sucking the juice of the tree. This they 
effect by means of a beak ending in a fine bristle. This 
is insinuated into the hark and the sappy part of the 
wood, and through it the ci'eature extracts, as through 
a syringe, the sweet liquor that forms as it were the 
life-blood of the branch. This long bristle is not to 
be seen in every specimen. In those possessing it, it 
is of different lengths, and is usually kept closely con- 
cealed under the breast. In the younger specimens it 
may be seen protruding like a fine termination to the 
anus ; but as the bodies lengthen, the bristle is soon 
concealed from view.” 
Mr. Knapp continues as follows: — “ The alburnum, or 
sapwood, being thus wounded, rises up in excrescences 
and nodes all over the branch and deforms it; the limb, 
deprived of its nutriment, grows sickly ; the leaves turn 
yellow, and the part perishes. Branch after branch 
is thus assailed, until they all become leafless, and the 
tree dies.” 
The Eriosoma, not having wings, is dispersed by 
means of this downy covering, ivhich is wafted by the 
winds in small tufts, so that the creature is conveyed 
with it from tree to tree throughout the whole orchard. 
In the autumn this substance is generally long, and the 
insects being dispersed by the winds and rains which 
are then prevalent, try to secrete themselves in any 
crannies they can find. There are no data to tell 
us when first this noxious insect visited us. America, 
Normandy, and the Netherlands have all been sup- 
posed to be the sources whence it was derived. Our 
climate, at all events, seems to be very favourable to 
its increase. 
* Journal of a Naturalist, p. 337. 
In 1745 Bonnet published his wonderful observa- 
tions on the reproduction of the Plant-lice,* and proved 
that the mother produced her young when no male 
insect was present. “ He isolated the young Aphis as 
soon as it was hatched. On the eleventh day the Aphis 
produced a young one alive; another succeeded, and 
another. Every four-and-twenty hours the brood was 
increased by three, four, and even ten arrivals. At the 
end of twenty-one days ninety-five young ones were 
produced from this single Aphis. Carrying further his 
observations. Bonnet found that the virgin offspring of 
this virgin parent also became parents ! We know 
that this reproduction often goes on till the eleventh 
generation ; then this process ceases, the last genera- 
tion is of perfect insects, with separate sexes, and these 
produce ova which next year become the productive 
virgins we have just been reading of.” The rate of 
increase may be conceived by the following calculation. 
The Aphis produces each year ten larviparous broods, 
and one which is oviparous ; and each generation 
averages one hundred individuals. 
Generation. 
Produce. 
1st, 
. 1, aphis. 
2nd, 
. 100, a hundred. 
3rd, . 
. 10.000, ten thousand. 
4Lh. . 
. 1,000,000, one million. 
5lh, 
. 100,000,000, one hundred millions. 
6th, 
. 10,000,000,000, ten billions. 
7th, . 
. 1 ,000,000,000,000, one trillion. 
8th, . 
. 100,000,000,000,000, hundred trillions. 
9th, 
. 10,000,000,000,000,000, ten quatrillions. 
10th, . 
. 1 ,000,000,000,000,000,060, one quintillion. 
Professor Huxley has made some very curious re- 
searches on the reproduction of the Aphides,f in which 
he ascertains that the virgin viviparous aphis produces 
its broods of young from unfertilized ova, while the 
female oviparous aphis produces her young from ova 
fertilized by spermatozoa, and that both broods in their 
early stages are similar. 
On the family Aleyrodidas, which is so prolific, 
I have neither room nor time to enter. 
Family- COCCID AH. 
This family of insects, which contains the well-known 
Cochineal, is a most anomalous one. The females are 
always wingless, and in their last state deposit their 
eggs and very speedily perish ; their dried up bodies 
serving as a cover and protection to the eggs. The 
mates of these insects are small fellows, not at all 
resembling their females in any particular either of 
form or habit. They are active, and have only two 
wings developed, which they use by flying about in 
the bright sunshine ; the place of the second pair 
of wings is supplied by two small projections some- 
what like the poisers of flies. But to return to the 
females, Mr. AVestwood,J speaking of the whole family, 
says, that without referring to their singular habits, “we 
find some of them on arriving at their last state so far 
departing from the typical characters of the winged 
insects, as to prove that Ptilota may exist, which in the 
imago state are not only wingless, but also footless and 
* Iiisectotheologie, vol. i. 
t Proceedings of the Linna3an Society, Nov., 1857. 
t Arcana Entoraologica, vol. i. p. 21. 
