ORDER COLEOPTERA 



185 



seems anomalous. It must be remembered, however, that 

 some of the wood borers work in the thin sheet of soft and 

 juicy cambium tissue between hard wood and bark and 

 that this limited environment is not very different from 

 the thin layer of tissue in a leaf. In the case of the weevils 

 the leaf -miners have perhaps been developed from the stem- 

 dwellers through petiole borers and forms that live in the 

 large ribs of leaves. The Chrysomelidae as a family are 

 attached to leaves and it seems rather natural that some of 



Fig. 55. Heads of two leaf mining beetles, 

 phora; C, Mandible; D, Maxilla; E, Labrum. 



A, Phyllotreta; B, Zeugo- 



the smaller ones should have sought protection by burrow- 

 ing in leaf interiors. 



The leaf-mining Coleoptera are particular in the selection 

 of their host plants. They resemble the Lepidoptera and 

 the Hymenoptera in this respect but differ from the Diptera 

 which are, as a rule, general feeders. Brachys and Trachys 

 have been found almost entirely on the woody plants, 

 although there are European records of Trachys reared from 

 mines on the leaves of Malva rotundifolia. Taphrocerus 



