APHID.*:. 



171 



both sexes ; antennae with six, seven, or eight joints; 

 females generally apterous ; tarsi with the last joint 

 vesiculous ; upper wings in the males larger than the 

 lower ; head transverse. 



This family contains the genus Aphis, of Linnaeus. 

 Antennae setaceous or filiform, seven jointed ; elytra 

 larger than the wings, elongate, triangulate ; abdomen 

 towards the apex generally tuberculate or honied ; 

 eyes entire. Several other genera have recently 

 been added to the family. 



The animals of this genus are very numerous, and 

 destructive at times to almost every species of plant. 

 There is a difficulty in preserving the species from 

 their being minute and soft, but we should recommend 

 the entomologist who would wish to make himself ac- 

 quainted with the numerous species already described 

 to attach to each specimen the name of the plant on 

 which it was found. The most familiar name by 

 which they are generally known in this country, i.s 

 plant lice, the French call them pitcerons. The 

 minute animals of this genus live entirely on vegeta- 

 bles, and the loftiest tree is as liable to their attacks 

 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, doing 

 irreparable 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 the most ten- 

 der, but because it affords them protection from the 

 weather, and from various injuries to which they 

 would be otherwise exposed. Sometimes, though 

 very rarely, the root is the object of their choice, and 

 the roots of lettuces have been observed so thickly 

 beset with one of the species that the whole crop has 

 been rendered sickly and of little value. They are 

 rarely, except one species (aphis salicis, which is larger 

 and much stronger than the others), to be found on 

 the bark of trees. 



These insects are sometimes winged, and sometimes 

 destitute of wings, this variation not depending upon 

 thedistinctionofsex. In the spring they are viviparous, 

 producing the young alive; and in the autumn they are 

 oviparous, depositing their eggs,like mostotherinsects, 

 in places where they remain secured 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 the 

 female is sufficient for nine generations. Their beak, 

 the sheath of which is composed of five joints, is in- 

 flected. The antennae are tapering, and longer than 

 the thorax. They have either four wings, or are en- 

 tirely destitute of them. At the extremity of the 

 abdomen there are two obtuse erect horns ; and the 

 tail is sometimes terminated by a small style. 



The larvae and perfect insects are said to have so 

 little difference in external appearance that they can- 

 not be distinguished from each other, except by size. 

 Aphis Rosce. This insect, which is well known by the 

 name of rose louse, is generally of a green colour ; with 

 the tip of the antennae and horns black. The tail is 

 pointed and without a style. Towards the beginning of 

 February, if the weather be sufficiently warm to make 

 the buds of the rose tree swell and appear green, 

 this species of aphis will be found on them in con- 

 siderable abundance. They are produced from small 

 black oval eggs, which were deposited in autumn 

 on the last year's shoots. If after their appearance the 

 weather become cold, almost the whole of them 



suffer, and the trees are, for that year, in a great 

 measure freed from them. 



Those that withstand the severity of the weather, 

 seldom arrive at their full growth before April, when, 

 after twice casting their skins, they usually begin to 

 breed. It then appears that they are all females, and 

 each of them produces a very numerous progeny, and 

 that without any intercourse with a male insect. 

 These, though themselves produced from eggs, are 

 viviparous. Their young, when they first come from 

 the parent insects, are each enveloped in a thin 

 membrane that has the appearance of an oval egg. 

 This apparent egg adheres by one extremity to the 

 mother, while the young aphis proceeding from it 

 extends the other, by this means gradually drawing 

 the ruptured membrane over the head and body to 

 the hind feet. During the operation, and for some 

 time afterwards, the forepart of the head adheres, by 

 the viscous matter about it, to the tail of the parent. 

 Thus suspended, it soon entirely frees itself from its 

 former envelopernent ; and when its limbs become a 

 little strengthened, it is set down on some tender 

 shoot, and there left to provide for itself. 



In the spring months there appear but these two 

 generations of the aphis : the warmth of summer, 

 however, produces no less than five. One of these 

 comes forth in May, and the months of June and July 

 supply each two more. The insects of the May 

 breed cast their skins twice, and the others three or 

 four times, according to the warmth of the season. 

 When the heat has been sufficiently great, and the 

 food in tolerable plenty, the first change has been 

 observed to take place in about ten days after their 

 production. 



Early in June some of the third generation, which 

 were produced about the middle of May, after casting 

 their last covering, exhibit four erect wings much 

 longer than their bodies. The possession of the wings 

 seems to depend not on sexual distinction, nor even 

 on the original structure of the insects, so much as on 

 the quantity and quality ot the nourishment with 

 which they are supplied. Few of those on 

 succulent shoots have wings, while those of the same 

 generation on the less tender branches are most of 

 them winged. Some time before they come to their 

 full growth, it is easy to discern which of them will 

 have wings, from a remarkable fulness of the breast. 

 When the last covering is thrown off the wings, which 

 were before folded in a very narrow compass, gra- 

 dually extend in a most beautiful manner to their pro- 

 per size and dimensions. All the following breeds 

 are winged. In the autumn, the eighth, ninth, and 

 tenth generations are produced ; two in August, and 

 the last about the middle of September. The two 

 first resemble the summer breeds, but the third differs 

 very greatly from all the rest. Though all the 

 aphides which have hitherto appeared have been 

 females, in this tenth generation several male insects 

 are found. The females have at first the appearance 

 of the summer insects, but in a few days their colour 

 changes from green to yellow, and gradually, before 

 their full growth, to orange. These yellow females 

 are destitute of wings. The males, when they first 

 appear, are of a reddish-brown, but have afterwards, 

 when they begin to thicken about the breast, a dark 

 line along the middle of the back. They come to 

 their full growth in about three weeks, and then, 

 casting their lust skin, appear in every part, except 

 the wings, of a bright yellow. They soon, however, 

 become dark brown ; the wings become transparent, 



