SURROUNDINGS OF GROWING INSECTS 209 



feeding habits as the leaf-miner Lyonetia clerckella and 

 the Codling (Carpocapsa pomonella) are usually confined to the 

 apple, though the latter may be observed, on occasion, feeding 

 in growing pears and plums also. As an example of a very 

 common insect with closely restricted feeding habit the Small 

 Tortoiseshell butterfly (Vanessa urticae) may be mentioned ; 

 its spiny caterpillars are to be seen only on stinging-nettles, 

 and the same is the case with its ally the Peacock butterfly 

 (Vanessa io). 



Reference has been made to willows as the original home and 

 food-supply of some of the capsid bugs that suck sap from 

 growing apples. The willows including the various forms of 

 osiers and sallows harbour an assemblage of insect larvae 

 as interesting as those found in apple orchards, and illustrating 

 some further features of life-relations. The big caterpillars 

 of the Eyed Hawk-moth (Smerinthus ocellatus) feed on willow 

 leaves as readily as on apple foliage, while the small, active 

 larvae of a gelechiid moth (Depyessaria conterminella] may be 

 found at the ends of osier shoots in late spring, having provided 

 for themselves a shelter by rolling the narrow, elongate leaves 

 and fastening them together by means of their silken threads. 

 Passing over a large assemblage of moth-caterpillars that feed 

 on the leaves of willows, as well as on those of other deciduous 

 trees, special mention may be made of the feeding habits of 

 the larvae of the beautiful yellow " Sallow " moths (Xanthia 

 flavago and X. fulvago). Emerging from the eggs, which, laid 

 in autumn by female moths, are the wintering stage of these 

 species, the caterpillars begin in spring to feed on the catkins 

 of sallows (Salix caprea), wherewith their pinkish mottled 

 coloration harmonizes well. Before they attain their full 

 growth the catkins may be withered, in which case the larvae 

 transfer themselves to plantain or bramble leaves. 



Besides caterpillars of many moths, those of several species 

 of saw-fly also feed on willows. The social larvae of Pteronus 

 salicis, for example, of which there are early summer and late 

 autumn broods, eat the foliage voraciously, so that only the 

 veins of the leaves escape destruction. But the willow-feed- 

 ing saw-fly larvae furnish interesting examples of that mutual 

 reaction between an insect and the plant on which it lives, 

 that results in the formation of a gall. Beneath willow-leaves 



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