THE ENTOMOLOGIST’S WEEKLY INTELLIGENCER. 127 
not only is the cylinder much flattened 
(though less so than in Antispila), but 
these larvEB are so attenuated at both 
ends that the form resembles more two 
cones meeting at their bases, — yet not 
two equal cones, but so proportioned that 
one should be three times as long as the 
other. These larva;, though they never 
quit the mine, are provided with legs, 
and have nearly the normal number; 
they have the six true legs, short but 
well defined, and eight prolegs. 
A more singular form is presented by 
the larv® of the genus Phyllocnistis ; 
their hinder extremity is so drawn out 
that it reminds us of the rat-tailed larvae 
amongst the Diptera, though the object 
of the prolonged tail in the Phyllocnistis 
larvae is very different. Tliese larvae are 
also perfectly apodal, and the structure of 
the mouth is peculiar: the jaws of all 
other Lepidopterous larvae terminate in 
two sharp-pointed mandibles ; the man- 
dibles of a Phyllocnistis are perfectly 
blunt and rounded, like the points of 
lace-scissors. The reason of this singular 
formation is pretty evident; the larvae of 
the genera Coleophora and Lilhocolletis, 
which mine in the interior ofleaves, feed 
on the parenchyma, which they detach 
piece by piece by their sharp mandibles 
and swallow ; but the the larvae of Phyl- 
locnistis, though feeding beneath the 
cuticle of the leaf, do not eat the paren- 
chyma, and a leaf eaten by one of these 
larvae, if held up to the light, shows no 
trace of the attacks of the larva. On what 
then do they subsist ? The larvae mine 
rather rapidly forwards beneath the 
cuticle, raising the cuticle from the epi- 
dermis, and they apparently devour 
something which they find between the 
two, which, as they do not seem to re- 
move any solid matter of the leaf, must 
be of a juicy nature. It is no doubt 
essential to the comfort of these larvae 
that the cuticle should not remain de- 
tached from the parenchyma in those 
parts of the leaf which the larva has 
passed over, and accordingly we find that 
the cuticle again becomes attached to the 
parenchyma immediately behind the 
larva, and that the cuticle may be let 
down gradually and gently is, I believe, 
the cause of the prolonged attenuated 
tail. The object of the blunt mandibles, 
in like manner, appears to be to avoid 
any risk of the larva piercing the cuticle, 
which by letting in the external air 
would probably be fatal to the existence 
of the larva, as these larvae have to move 
their jaws in constant juxta-position to 
the cuticle, which, in the aspen tree 
(which is frequented by the commonest 
species of the genus, P. suffusella), is re- 
markably thin, it must be a great con- 
venience to the larva that the structure 
of its jaws is such that it can eat its fill 
without any danger of piercing the 
cuticle. Sharp-pointed jaws are neces- 
sary to a larva which feeds on the harder 
parts of leaves, but to this, which only, 
as it were, sucks up the juice, sharp- 
pointed jaws are quite unnecessary. 
I have already noticed that if a leaf 
eaten by this larva be held to the light 
no symptoms of its operations will be 
apparent; but if, instead of holding the 
leaf between us and the light, we look 
down on it slantways we shall perceive 
some slightly iridescent tracks, which 
have very much the appearance as 
though a snail had been crawling across 
the leaf. 
Another peculiarity of this larva is 
that it never moults ; its skin is ap- 
parently of so elastic a nature that it 
grows with the larva; most larvae cast 
their skins four or five times in the 
course of their lives, but this larva never 
