LEPIDOPTEEA. (mOTHS). 



191 



much in habits as in structure : some are miners, forming fine 

 tunnels in leaves ; some roll up leaves ; the ColeopJioridc^ live 

 in peculiar cases almost like snail-shells (fig. 88, a) ; clothes form 

 a shelter for one group, and numberless others live in a variety of 

 ways. Amongst the injurious species we must at least mention 

 the well-known 



Diamond-bacJc Moth {Plutella cruciferarum). 



In 1891 the east coast of Great Britain was ravaged by count- 

 less numbers of this minute moth, whose larvee feed on turnip, 

 cabbage, and most other cruciferous plants, devouring the 

 leaves down to the midrib. It was estimated that in a single 

 year this little pest, which is well known over most parts of 

 England, caused £20,000 worth of damage to root-crops alone. 

 Before that year and 

 since it has done harm 

 in many districts. Tlie 

 moth, which is a na- 

 tive, has long narrow 

 wings, the fore pair 

 being reddish- or slaty- 

 brown, with a pale 

 yellowish - white bor- 

 der posteriorly ; the 

 hind-wings are grey, 

 with long fringes of 

 hair, a feature seen in 

 all Tineinas. When the 

 wings are folded the pale edges of the front ones come close to- 

 gether, and form diamond-shaped areas, hence its popular name. 

 The moths (fig. 87) appear in June and July, and lay their eggs 

 on the under-side of the leaves. The lar\';c are at first grey, tlien 

 green in colour, about half an inch long when full grown : they 

 feed ravenously on the under-side of the leaf, ^^']len frightened 



Fla. 87. — IJLAMOND-BACK MoTH (Flutclla 

 cruciferaruvi). (Wliitehead.) 



Moth, larva, and cocoon (nat. size, and magnified). 



