INTRODUCTION. 
61 
The stemmatic, or simple eyes, in the form of pel- 
lncid spots, are usually two in number, and placed 
on the crown of the head. They are probably of- 
ten awanting, and, when present, are so indistinct, 
from being covered by the hairs and scales that clothe 
the surface, that their existence in any case among 
the diurnal Lepidoptera has been sometimes denied. 
The antennae are of moderate length, and consist 
of a great number of joints, which usually increase in 
thickness towards the extremity, where they form a 
club or knob. (PI. I. fig. 12, 6). They are greatly 
more uniform in appearance and structure than in the 
coleopterous or most other tribes, or in the nocturnal 
species of the same order, which often have them beau- 
tifully branched, and plumose. The shape of the ter- 
minal knob, however, varies considerably, and as its 
different forms afford useful characters for distin- 
guishing genera, they will be afterwards particularly 
indicated. 
The thorax — that portion of the body interme- 
diate between the head and abdomen — is composed 
of three segments, so closely united as apparently to 
form a single piece. Its most ordinary form ap- 
proaches to cubical, any apparent deviation from that 
shape being chiefly caused by the greater length and 
density of the hairs and scales with which it is co- 
vered. Before the insertion of the upper wings, 
two corneous scales may be observed, covered with 
tufts of hairs, so as to make them resemble an epau- 
let : these have received the name of patagia, or 
