82 
BBITISH APHIDES. 
a Sy^'phiis. It is suggested that these bodies may have 
misled the above and other authors. 
Examples of the mode of grouping ova, either in 
small isolated patches or in collections of a hundred 
or more, may be seen in the plates devoted to the 
species Sijphonophora rosce, GJiaitophorus aceris, Ghermes 
laricis and picece^ and Phylloxera querms. 
The Aphis just extruded from the egg is not much 
smaller than the adult, but it shows many differences 
as to its general contour, the proportions of its 
antennse, its cornicles, and its legs. The first of these 
organs are often in a rudimentary condition. Through 
a suppression of some of their joints they are usually 
much shorter than we find in the adult. The last joint 
is often unformed and very simple. The third joint is 
the longest, and by its constrictions in certain parts, in 
after broods, it finally develops the normal number 
of seven articulations, which full complement, how- 
ever, occasionally only appears in the winged form. 
This must be remembered whilst deciding on a genus. 
The legs of the young insect are very stout and short. 
The tarsi and claws are large, and the cornicles, if 
present, have perhaps only a quarter of their normal 
length. The young, after their emergence from the 
egg, are active ; and as their occupation is to grow as 
fast as possible, the rostrum, with its enclosed setse, is 
fully developed — often, indeed, to such an abnormal 
extent that it forms an awkward appendage trailing 
behind the body whilst walking. The young insects 
will often hatch out in the coldest weather. Very 
probably light, which is as necessary as heat for the 
elaboration of both the insect and its food, is here one 
of the chief stimuli. 
As the Aphis grows it assumes more of the normal 
form of the larva, whilst simultaneously a large 
increase is to be noticed in the size of the pseud- 
ovarian sacs, which begin to occupy the principal part 
of the abdomen. Development of the germs within 
these sacs proceeds at different rates, the most forward 
