190 A BOOK OF INSECTS 



of a meadow in which cattle have been grazing is rapidly 

 benefited by a fairly even distribution of manure among 

 the roots of the turf. 



Although the vast majority of insects are either 

 carnivorous or vegetarian, the gap between the two 

 groups is bridged over by a few species which affect 

 a mixed diet. Some cockroaches may almost be termed 

 omnivorous, for they seem to relish any edible substance 

 that comes their way ; and earwigs devour the larva? of 

 other insects, and small molluscs, as well as fruit and 

 parts of flowers. Social wasps supply their young first 

 with nectar or fruit juice, and later with the soft tissues 

 of slaughtered insects, or fragments of meat ; while many 

 ants feed indiscriminately upon any food that they have 

 the luck to discover. Certain butterflies — our own 

 purple emperor (Apatura his) for example — are attracted 

 by the odours and juices of putrefaction, while some 

 caterpillars subsist upon substances of animal origin, such 

 as wool, feathers, and wax. A few prey upon other 

 insects. Those of a Southern European owl-moth 

 {Erastria scitula) devour scale insects, and form pro- 

 tective cases from the shells of their victims mingled with 

 their own excrement. The caterpillar of the common 

 dun-bar moth (Cosmia trapeziiia), though it feeds normally 

 upon oak and other leaves, is known to be an inveterate 

 cannibal. 



