70 BRITISH INSECTS 



Other Chrysomelid species are the dainty little 

 asparagus-beetle, 1 the much-dreaded Colorado-beetle, 

 or " potato-bug," 2 and the diminutive turnip and 

 cabbage " fleas " of the genus Phyllotreta. Indeed, very 

 many members of the family are highly injurious to 

 cultivated crops. The attractively coloured, riverside 

 beetles of the genus Donacia are, happily, free from 

 this stigma. Their life-stories present some very 

 unusual features. The larvae feed on the submerged 

 roots of aquatic plants. Their method of breathing 

 is peculiar, for they have two sharp-pointed tubular 

 processes near the tip of the abdomen, and by driving 

 these into the air-spaces of the plant's tissues they 

 contrive to extract sufficient oxygen for their needs. 

 So far as the writer is aware, no other insects are 

 known to breathe at the expense of their food-plants ! 



Before leaving the Chrysomelidcz, the curious tortoise- 

 beetles of the genus Cassida must be mentioned. They 

 and their allies constitute a very distinct group or sub- 

 family. When at rest, the insect's body and its ap- 

 pendages are completely hidden beneath the pronotum 

 and elytra, which are unusually broad and flat. The 

 common Cassida viridis, found upon thistles, looks more 

 like a small green blister on the stern or leaf than a 

 living insect. The larvae of this and other species 

 have the strange habit of covering their bodies with 

 their own dried excrement, the matter being held in 

 place by a kind of fork, situated at the posterior ex- 

 tremity. 



The Longicorns 3 may be easily recognized by their 

 oblong form, long antennae, and kidney-shaped eyes. 

 The typical larvae of the family have hard heads and 



1 Cnoceris asparagi. 2 DoryphorA decemlineata. 



3 Cemmby tides. 



