196 Mr. F. Walker's Descriptions of Aphides. 



base j the third is obsolete at its source, and is forked before one- 

 third and again after two-thirds of its length, but this arrange- 

 ment is subject to exceptions ; the first and the second veins are 

 almost straight, and the distance between them at the base is 

 about half of that at the tips. The cultivation of the rose has 

 much extended the habitation and increased the nourishment 

 of this species, and its habits have been probably modified by an 

 alteration of the temperature, as made known to us by geological 

 investigations. In former ages, when severer frosts were the re- 

 sult of greater elevation of the land, the viviparous faculties of 

 this Aphis must have been limited to the summer season. Among 

 the particulars of its history yet to be ascertained are how far its 

 presence is coextensive with the rose and other plants which are 

 its food, whether it is confined to the rose where it has not the 

 means of migrating to the teasel and the scabious, and in what 

 regions the ants and its devourers accompany it or are replaced 

 by other species. 



The winged male. While a pupa it is bright red, and exhibits 

 a striking contrast to the pale velvet-like oviparous female of 

 Aphis dirhoddywhich sometimes swarms on the rose-bushes in 

 the autumn. When the wings are unfolded it is black : the ab- 

 domen is dark yellowish green ; most of the disc is black, and 

 there is a row of black spots on each side : the feelers are much 

 longer than the body : the mouth and the nectaries are dull yel- 

 low with black tips, and the latter are nearly one-fourth of the 

 length of the body : the thighs are pale yellow towards the base ; 

 the shanks with the exception of their tips are dark yellow ; the 

 wing-ribs and the rib-veins are pale yellow; the wing- brands and 

 the veins are brown. 



" The females (of the tenth generation) have at first altogether 

 the same appearance with those of the former generations ; but 

 in a few days their colour changes from a green to a yellow, 

 which is gradually converted into an orange colour, before they 

 come to their full growth. They differ likewise in another re- 

 spect, at least from those which occur in the summer, that all 

 those yellow females are without wings. The male insects, when 

 first produced, are not of a green colour, like the rest, but of a 

 reddish brown ; and have afterwards when they begin to thicken 

 about the breast, a dark line along the middle of the back. These 

 male insects come to their full growth in about three weeks time, 

 and then cast off their last covering ; the whole insect being after 

 this operation of a bright yellow colour, the wings only excepted. 

 But they soon change to a darker yellow, and in a few hours to a 

 very dark brown ; if we except the body, which is something 

 lighter coloured, and has a reddish cast. They are all of the 

 winged sort ; and the wings, which are white at first, soon become 



