142 NATURAL ARRANGEMENT OP INSECTS. 



are upon appears covered with white cotton, which, if 

 touched by the tinger, separates into distinct tufts, — an 

 effect produced by the animals being suddenly disturbed, 

 and then moving in all directions. \Vhen this cotton is 

 brushed off, the larva appears of a pale green colour, 

 varied with black spots, ^^'hen arrived at its complete 

 or perfect state, by casting its pupa skin, it is entirely 

 green, with transparent wings. If disturbed, it leaps 

 with great agility, frequently flying at the same time.* 

 (132.) The true Aphides, or plant lice, are well 

 known to infest the early buds of the rose tree and 

 other plants, upon which they continue to multiply 

 during the whole of summer. The habits and economy 

 of these singular insects are so well known, that we shall 

 here chiefly confine our remarks to their external cha- 

 racters, and their general history. The body is thick, 

 fat, and round, having, towards the end, three horn-like 

 bristles, one of which is on each side, the other at the 

 vent ; these terminate ia a little knob, and are move- 

 able ; their use, however, does not appear to have been 

 detected : the head and eyes are very small, — the latter 

 prominent; while the antennae, unlike those of aU the 

 other families, are as long as the body, slender, filiform, 

 and composed of seven joints : the Avings also differ 

 greatly from aU other hemipterous insects ; they are 

 perfectly transparent, and distinctly veined, — assimi- 

 lating, in short, to those of the hyraenopterous order. 

 Like those insects, they have likewise the power of 

 forming a honey-like secretion from the vegetable juices 

 upon which they subsist, although by a totally different 

 process. In most species of the Aphides, both males 

 and females acquire wings at certain seasons; but in this 

 respect they are subject to great variation, — there being 

 some males and some females that never have wings ; 

 again, there are some females that become winged, 

 while others of the same species do not. The Aphides 

 are the most defenceless of aU insects, for they can nei- 



* Shaw, Gen. Zool., vi. 1187. 



