260 HABITATIONS OF INSECTS. 
fishes which have fins upon their backs. The opposite side they are neces. 
sarily forced to cut and sew up; but even in this operation they show an 
ingenuity and contrivance worthy of admiration. The moths which cut out 
their suit from the middle of the leaf wholly detach the two surfaces that 
compose it before they proceed to join them together ; the serrated incisions 
made by their teeth, which, if they do not cut as fast, in this respect are 
more effective than any scissors, interlacing each other so as to support 
the separated portions until they are properly joined. But it is obvious that 
this process cannot be followed by those moths which cut out their house 
from the edge of a leaf, If these were to detach the inner side before they 
had joined the two pieces pa als the builder as well as his dwelling 
would inevitably fall. They therefore, before making any incision, pru- 
dently rwn (as a sempstress would call it) loosely together in distant points 
the two membranes on that side. Then putting out their heads they cut 
the intermediate portions, carefully avoiding the larger nerves of the leaf; 
afterwards they sew up the detached sides more closely, and only intersect 
the nerves when their labour is completed.! The habitation made by a 
moth which lives upon a species of Astragalus is in like manner formed of 
the epidermis of the leaves ; but in this several corrugated pieces project 
over each other, so as to resemble the furbelows once in fashion.? 
Other larva construct their habitations wholly of si/t. Of this deserip- 
tion is that of a moth, whose abode, except as to the materials which 
compose it, is formed on the same general plan as that just described, and 
the larva in like manner feeds only on the parenchyma of the leaf. In the 
beginning of spring, if you examine the leaves of your pear trees, you will 
scarcely fail to meet with some beset on the under surface with several 
perpendicular downy russet-coloured projections, about a quarter of an 
inch high, and not much thicker than a pin, of a cylindrical shape, with a 
protuberance at the base, and altogether resembling at first sight so many 
spines growing out of the leaf. You would never suspect that these could 
be the habitations of insects ; yet that they are is certain. Detach one of 
them, and give it a gentle squeeze, and you will see emerge from the lower 
end a minute caterpillar, with a yellowish body and black head. Examine 
the place from which you have removed it, and you will perceive a round 
excavation in the cuticle and parenchyma of the leaf, the size of the end 
of the tube by which it was concealed. This excavation is the work of 
the above-mentioned caterpillar, which obtains its food by moving its little 
tent from one part of the leaf to the other, and eating away the space im- 
mediately under it. It touches no other part; and when these insects 
abound, as they often do, to the great injury of pear trees %, you will perceive 
every leaf bristled with them, and covered with little withered specks, the 
vestiges of their former meals. The case in which the caterpillar resides, 
and which is quite essential to its existence, is composed of silk spun from 
its mouth almost as soon as it is excluded from the egg. As it increases In 
size, it enlarges its habitation by slitting it in two, and introducing a stip 
of new materials. But the most curious circumstance in the history 0 
this little Arab, is the mode by which it retains its tent in a perpendicular 
posture, This it effects partly by attaching silken threads from the pro- 
tuberance at the base to the surrounding surface of the leaf. But being not 
1 Reaum, iii. 100—120. 2 Tbid, 146, 
5 Forsyth on Fruit Trees, 4to, edit. 271, 
