60 
INTRODUCTION. 
They are attached to a triangular plate, which must be 
regarded as the labium or under lip, as it closes the ca- 
vity of the mouth, immediately below the insertion of 
the trunk. On each side of the latter, not far from the 
base, there is a minute tuherculiform projection, formed 
of two or three indistinct joints, which together seem 
to represent the maxillary palpi. The representative 
of the labrum or upper lip, is a minute membranous 
piece, usually approaching to a triangular shape ; and 
two other small projections, more or less ciliated in- 
ternally, and placed one on each side of the probos- 
cis at the base, are analogous to the mandibles of 
gnawing insects. Most of these parts, however, ex- 
ist in a very rudimentary condition, and afford an- 
other example, in addition to many already familiar 
to us, of nature adhering to a particular form of struc- 
ture, after it has ceased to be subservient to any es- 
sential function ; for, if some of these parts are de- 
signed for the same purpose which they serve so ef- 
fectively when fully developed, it is not easy to see 
how they could be employed by the insect, or in any 
way prove serviceable to its economy. 
Both the different kinds of eyes which occur among 
insects , are to be found in the diurnal Lepidoptera. 
The ordinary, or compound eyes, are large and he- 
mispherical, occupying greater part of the head, and 
no fewer than 17,325 lenses have been counted in 
one of them. As each of these crystalline lenses 
possesses all the properties of a perfect eye, some 
butterflies may therefore be said, if M. Puget’s ob- 
servations are correct, to have no fewer than 34,650, 
