14 
BRITISH APHIDES. 
habits create wants which are supplied by these more 
highly developed organs. 
The hard basal joints of the antennse are attached to 
the head, or to the frontal tubercles, by a supple mem- 
brane, which permits the freest play. Some species 
keep their antennse in more or less continuous vibra- 
tion: 
In Schizoneura and allied genera, the joints of the 
antennse are elegantly formed of cup-like bodies, which 
are inserted one within another. In other forms a 
ringed character may be detected {vide Plate A, fig. 7). 
It is not difficult to trace in some transparent \ 
species a fine nervous filament which traverses the ? 
v/hole length of the antennae. It proceeds from a ' 
plexus of nerves situated near the base of the rostrum, 
in the centre of the head. This filament is compound 
on leaving the plexus, but appears to become single 
on entering the antenna, or more probably from the 
place they enter they are enclosed in one common 
sheath. Possibly these nerves may be cognizant of 
vibrations transmitted through the fluids which bathe 
the interior of these organs. 
The antennae vary much in length. In some genera 
they scarcely equal in length the breadth of the head ; 
in other genera they may reach to the base of the 
abdomen, whilst in Siphonophora and Callipterus they 
have their full development, and often very much 
exceed the length of the body. 
THE EYES. 
Aphides, with the exception of some of the root- 
feeding species, are very completely furnished with 
these organs. They appear in the embryo at an early 
stage, and then may often be seen to dot the trans- 
parent skin of their mothers, as brilliant red spots. 
The large compound eyes are constructed much after 
the plan seen in the Diptera and Hymenoptera, but it 
will be noticed, that instead of their being facetted with 
