390 



HABITATIONS OF INSECTS. 



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 larvae construct their habitations wholly of silk. Of 

 this description 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 grow- 

 ing out of the leaf. You would never suspect that these 

 could be the habitations of insects ; yet that they are is cer- 

 tain. Detach one of them, and give it a gentle squeeze, and 

 you will see emerge from the lower end a minute caterpillar, 

 with a yelloAvish 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 cater- 

 pillar, which obtains its food by moving its little tent from 

 one part of the leaf to the other, and eating away the space 

 immediately 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. 



1 Keaum.iii. 100—120. 



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



2 Ibid. 146. 



