THEIR RELATION TO PLANTS 



81 



beaded antennae. Their larvae are little footless grubs, 

 peculiar by having a single chitinous rod or anchor- 

 like structure known as a breast-bone, which serves 

 to scrape the plant tissue on which the creature feeds. 

 These gall-midges or Cecidomyiids attack a great va- 

 riety of plants at all sorts of points, and cause a great 



FIG. 33. The pear midge, Diplosis pyrivora: a, female adult; c, pupa; other 

 references to structural details. 



variety of deformations that are commonly known 

 as galls, although they differ totally in character from 

 the galls caused by the Cynipids. For instance, the 

 pear midge lays its eggs in the pear blossom; the 

 larvae enter the seed capsule of the fruit and the latter 

 becomes somewhat abnormal in shape so that to the 

 practised eye the galling is perceptible. The Hessian 

 fly lays its egg in the sheath of the wheat leaf near 

 6 



