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HISTORY OF INSECTS. 



The animal which some have called the 

 Leaf-Louse, is of the size of a flea, and of a 

 bright green, or bluish-green colour ; the body 

 is nearly oval, and is largest and most convex 

 on the hinder part; the breast is very small, 

 and the head is blunt and green : the eyes may 

 be seen very plainly, being prominent on the 

 fore part of the head, and of a shining black 

 colour ; near these there is a black line on 

 each side ; and the legs are very slender. 1 



These animals are usually found on the 

 leaves of the orache, and other plants ; and the 

 weaker the leaves and buds are, these insects 

 swarm upon them in greater abundance. Some 

 plants are covered over with them ; though 

 they are not the cause of the plant's weakness, 

 but the sign : however, by wounding and suck- 

 ing the leaf, they increase the disease. They 

 generally assume their colour from the plant 

 on which they reside. Those that feed upon 

 pot-herbs and plum-trees, are of an ash-colour; 

 only they are greenish when they are young : 



1 Of the Aphides, or Plant Lice. The minute ani- 

 mals which compose this singular tribe live entirely on 

 vegetables, and the loftiest trees are as liable to their at- 

 tacks as the most humble plant. Their numbers are 

 often incalculably great. They prefer the young shoots 

 on account of their tenderness, and frequently insinuate 

 themselves into the very hearts of the plants, doiug irre- 

 parable mischief even before they are discovered. But 

 for the most part they beset the foliage, and are always 

 found on the under side of the leaf. This they prefer, 

 not only on account of its being most tender, but because 

 it affords them protection from the weather. 



Some of the species are constantly and unalterably at- 

 tached to one or more particular kind of plants ; but 

 others feed indiscriminately on most sorts of herbage. 



These insects are sometimes winged, and sometimes 

 destitute of wings, without any distinction of sex. In 

 the spring they are viviparous, producing their offspring 

 alive; and in the autumn they are oviparous, depositing 

 their eggs, like most other insects, in places where they 

 remain secure through the winter till the ensuing spring, 

 when they are hatched. The aphides afford also another 

 surprising deviation from the general laws of nature ; one 

 impregnation of a female is sufficient for nine genera- 

 tions. 



The larvae, chrysalides, and perfect insects, have so 

 little difference in external appearance, that they can- 

 not be distinguished from each other. 



If the aphides had not many enemies, their increase 

 in summer would be so great, as by wounding and ex- 

 hausting the tender shoots of the trees, sometimes to sup- 

 press their vegetation. Among their enemies, one of 

 the principal is a small black species of ichneumon-fly, 

 which darts its pointed tail into the bodies of the aphi- 

 des, and at the same time deposits an egg in each. This 

 egg afterwards produces a grub, which feeds on the body 

 of the insect till it has acquired its full growth, when it 

 undergoes its change, and entirely destroys its living 

 nidus. 



After a mild spring, most of the species of aphis be- 

 come so numerous as to do considerable injury to the 

 trees on which they are found. The best mode to re- 

 medy this evil is to lop off the infected shoots before the 

 iinects greatly multiplied, repeating the same operation 

 before the time that the eggs are deposited. By the first 

 pruning, a very numerous present increase will be pre- 

 vented ; and by the second, the following year's supply 

 may in a great measure be cut off. 



those that belong to the alder and cherry-tree, 

 are black ; as also those upon beans, and some 

 other-plants : those on the leaves of apples and 

 rose-trees, are white : but as they leap, like 

 grasshoppers, some place them in the number 

 of the flea kind. The most uncommon colour 

 is reddish ; and lice of this sort may be found 

 on the leaves of tansey ; and their juice , when 

 rubbed in the hands, tinges them with no dis- 

 agreeable red. All these live upon their res- 

 pective plants ; and are often engendered with- 

 in the very substance of the leaf. 



All these bring forth their young alive ; and 

 the foetus, when it is ready to be brought forth, 

 entirely fills the belly of the female ; its fore 

 parts being excluded first, and then the hin- 

 der. The young one does not begin to move 

 till the horns or feelers appear out of the body 

 of the old one ; and by the motion of these it 

 first shows signs of life, moving them in every 

 direction, and bending all their joints. When 

 the horns and head are excluded, the two fore- 

 feet follow, which they move with equal agi- 

 lity ; after this follow the middle feet, and 

 then the hinder : still, however, the young one 

 continues sticking to its parent, supported only 

 at one extremity, and hanging, as it were, in 

 air, until its small and soft members become 

 hardened and fitted for self-support. The pa- 

 rent then gets rid of its burden ; by moving 

 from the place where she was sitting, and for- 

 cing the young one to stand upon its legs, 

 leaves it to shift for itself. 



As the animal has not far to go, its provi- 

 sions lying beneath it, during the summer it 

 continues to eat and creep about with great 

 agility. But as it is viviparous, and must ne- 

 cessarily lurk somewhere in winter, where its 

 body may be defended from the cold, it endea- 

 vours to secure a retreat near the trees or plants 

 that serve to nourish it in the beginning of 

 spring. They never hide themselves in the 

 earth, like many other insects, because they 

 have no part of their bodies fitted to remove 

 the earth : nor can they creep into every chink, 

 as their legs are too long : besides, their bo- 

 dies are so tender, that the least rough particle 

 of the earth would hurt them. They, there- 

 fore, get into the deep chinks of the bark, and 

 into the cavities of the stronger stalks, from 

 whence they sally out upon the branches and 

 leaves when the warmth of the sun begins 

 to be felt. Neither the cold in the autumnal 

 season, nor the lesser degree of heat in the 

 spring, ever hurts them ; they seldom, there- 

 fore, seek for hiding-places before the fall of 

 the leaf, and are alert enough to take the ear- 

 liest advantage of the returning spring. 



Like many other insects, they cast their 

 skins four several times : and, what is very 

 remarkable, the males have four wings, but 

 the females never have any. They all have 



