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 together, the builder as well as his dwelling 

 would "inevitably fall. They therefore, before making any incision, pru- 

 dently run (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 o? Aslragrdus 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 larvae construct their habitations wholly oi silk. Of this descrip- 

 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 parenchj'nia 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 strip 

 of new materials. But the most curious circumstance in the history of 

 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 



» Eeaum. iii. 100—120. 2 Ibid. 146. 



3 Forsyth on Fruit Trees, 4to. edit. 271. 



