INSECTS. 



143 



separately, and on herbs, only a few species on trees. 

 The caterpillars are very much scattered, and the 

 damage caused by them is never great, except in spots 

 here and there, — on the contrary, when they increase 

 to a great extent they spread over a wider area. 

 Several species are harmful to agriculture. 



The Surface Caterpillars (Species of Agrotis) 



are stout caterpillars, IJ to 2 inches long, with five 

 pairs of pro-legs, and shining transparent external 

 skin. They remain in the ground during the day, 

 feeding above ground at night, and also in the day- 

 time when the sky is much overcast. When touched 

 they bend themselves into the form of a C There are 

 in Britain several species of surface caterpillars which 

 have these habits, but I will only describe here, to 

 begin with, the commonest kind : — 



The Common Dart or Turnip Moth (Agrotis segetvmi 

 or A. clavis). — Moth (Fig. 99) : Length almost f of an 



Fis. 99.— The Common Dart or Turnip Moth (Agrotis segetmri) with Caterpillar. 



inch. Span of wing about 1^ inch. Fore wings small, 

 ash-grey or brownish, with many dark patches and 



