PLUTELLA CRUCIFERARUM. 



47 



and are of a pale ashy grey colour. The body and legs 

 are brownish grey ; the head and thorax grey or ochreous 

 grey ; the antennae are brown, finely spotted with white. 

 The expanse of the wings is 14 16 millni. 



When this moth is at rest the front wings meet along 

 the back, and the projecting parts of the pale bands form 

 diamond-shaped marks, whence the English name of 

 " Diamond-back Moth." 



FIG. 21. Plutella cruciferarum. Moth (natural size and magnified), 

 caterpillar, and cocoon. 



A piece of cabbage-leaf, much injured by the workings 

 of the caterpillars, was sent over by Mr. Bairstow as a 

 sample of the damage caused by them : specimens of 

 the moths and caterpillars were also sent, together with 

 the following note by Mr. J. de Witt Meulen, of the 

 Winterhoek : 



" Larvae very numerous on young cabbage-plants in 

 June and July. Those placed in breeding-boxes covered 

 themselves, within three days, with a thin translucent 

 web, and remained about thirty days in the chrysalis 

 state. . . . Heavy rains or frequent watering of the 

 leaves destroys many grubs. If planted in rows, cab- 

 bages are protected on each side by a line covered with 

 glue or molasses ; many moths are prevented thereby 

 depositing their eggs on the plants." 



