SURROUNDINGS OF GROWING INSECTS 213 



cutting organs for making incisions in plant tissues ; it is simply 

 inserted between the leaves of the bud, so as to deposit the eggs 

 where the young larvae will owing to the plant's response to 

 their presence find effective shelter and abundant food. 



Several other kinds of gall-midge 1 inhabit willows during 

 their larval period. The female of Rhabdophaga saliciperda, 

 for example, lays her eggs on the bark in June and July, and 

 the larvae eat their way into the wood, where their presence 

 stimulates the growing tissue to produce irregular swellings 

 wherein they find shelter and food through the autumn and 

 winter, each yellow grub occupying a little oval chamber. In 

 the succeeding spring they pupate beneath the bark, and the 

 pupae work their way partly out of the shoots through small 

 round holes in the bark, from which the delicate white pupal 

 cuticles may be seen protruding after the emergence of the 

 midges in spring and early summer (Plate III) . The activities of 

 these insects may render the trees which they inhabit unsightly, 

 as the bark is ruptured so that it hangs down in shreds 

 on account of the abnormal growth of the underlying woody 

 tissue. In the case of these dipterous gall-midges, the 

 correlation between plant and insect is less complete and 

 harmonious than in the case of the hymenopterous gall-flies 

 of which examples have been given in connexion with oak- 

 trees, or the gall-forming saw-flies mentioned above as 

 characteristic insects of the willow itself. 



In summertime the leaves of willows and osiers are often 

 so severely eaten as to appear riddled and torn into multi- 

 tudinous holes. This is the work of the willow-leaf beetles 

 (Phyllodecta) (see p. no, Fig. 61) and their larvae. The small, 

 metallic, dark-hued beetles come out of winter quarters beneath 

 loose pieces of bark, the eaves of sheds and such shelters, and 

 lay their eggs on the leaves. The well-armoured larvae live 

 like their parent beetles, feeding openly on the willow-leaves. 

 The beetles, more than any other order of metamorphic insects, 

 afford examples of imago and larva, living and feeding in the 

 same manner, and this is in some cases correlated with loss 

 of power of flight on the part of the beetles. An extreme 

 instance of this tendency is afforded by the female of Lampyris, 



1 J. J. Kieffer : " Monographic des Cecidomyides d'Europe et d'Algerie ". 

 Ann. Soc. Entom. France, LXIX. 1900. 



