LEPIDOPTERA, 319 
sexes. Burmeister, Lefebvre, and Lacordaire have enumerated a 
considerable number of such instances. 
There is often very considerable diversity in the appearance of the 
sexes of these insects, the females being generally the largest, most 
dully coloured, with simple antenne: they are occasionally also 
destitute of wings (as in Orgyia, Cheimatobia, Lampetia, &c.), and 
even in Oiketicus and Psyche present but very little of the appear- 
ance of perfect insects, bearing a much greater resemblance to full- 
grown larvae. In some species, also, the opposite sexes are coloured, 
either entirely or partially different from each other, as in the ghost 
moth, muslin moth, or orange-tip butterfly, the female of which last 
has not the slightest tinge of orange on its wings. Another curious 
sexual diversity takes place in some of the Geometridz, the males of 
which have a large wing-like lobe at the base of the posterior wings, 
giving them the appearance of being six-winged (Lobophora sexali- 
sata, &c.). 
The transformations of these insects have attracted the attention of 
observers from the earliest times, owing to their common occurrence, 
large size, and the beauty of the insects in their perfect state. The 
eggs are far more variable in shape than in the other orders, their 
surface being often elaborately ornamented with raised lines, spots, 
&c., in many cases closely resembling Echini. ‘The larvae, which are 
commonly called caterpillars, are long and cylindrical, composed of 
thirteen segments, of which the anterior represents the head of the 
imago, and is succeeded by three segments, each of which mostly 
bears a pair of simple, short, and articulated feet. These segments 
represent the thorax, and the remainder the abdomen, of the butterfly 
or moth. Of these segments, the four intermediate ones, as well as 
the anal segment, are furnished with prolegs, as they have been 
termed, being thick, short, fleshy limbs, armed at the extremity with 
a very great number of minute recurved hooks, and furnished with 
powerful muscles, enabling the larva to retain strong hold of its place 
of rest. The number of these prolegs varies, however, from ten to 
four, the last pair, with a few exceptions (Cerura, Stauropus, &c.), 
being placed on the anal segment of the body.* The sides of the 
body are furnished with nine pairs of spiracles; the head is armed 
with a pair of powerful mandibles, a moderate-sized upper lip, often 
* One of the nocturnal genera has been termed Apoda Haw., Limacodes Latr., 
from being destitute of feet in the larva state. 
