309] NOCTVID LARVAE— RIPLEY 67 



that we may have in the remote future a larger number of species of sub- 

 terranean noctuid larvae than at present. However speculative this propo- 

 sition may seem, it is undoubtedly indicated by the data at hand. 



When we compare subterranean and non-subterranean larvae with 

 reference to the number of individuals parasitized, the advantage of the 

 former mode of life becomes obvious. From more than a thousand indi- 

 viduals of Feltia subgolhica reared during three successive years, but four or 

 five have been infested with insect-parasites, whereas larvae remaining 

 above ground during the daytime, such as the cabbage-looper or the army- 

 worm, are frequently 90*^ parasitized by many insect-enemies. Subter- 

 ranean cutworms are similarly free from attack by birds. Egg-parasites 

 affect both classes equally. Fungi and wilt diseases seem to be as generally 

 found in non-subterranean hosts as in those whose habitats are associated 

 with the earth. The only nematodes thus far recorded from noctuid larvae 

 were taken from a single subterranean cutworm, Agrotis sp., by the author. 

 The apparent rarity of these parasites in cutworms indicates that they are 

 not to be regarded as important enemies. Large carabid beetles are 

 evidently the only important natural enemies affecting subterranean 

 lepidopterous larvae to an appreciably greater extent than those which 

 do not enter the soil. Yet these feed extensively upon larvae above ground, 

 some even climbing trees in search of their prey. From the point of view of 

 protection from natural enemies, the subterranean habit unquestionably 

 offers important advantages, which probably accounts to a large extent for 

 its progressive nature in the course of evolution. 



The interpretation of certain exceptional curves in Plate I is proble- 

 matical. That of Agrotis dandestina fails to turn upward, altho the larva 

 of this species is to some extent subterranean. The primary lengthening 

 of the epicranial stem of this species is but slight in the last period, indi- 

 cating the retarding of this process, which must necessarily precede the 

 secondary shortening. Not only does the curve thus indicate an incipient 

 condition in the reduction of this suture, but the bright coloration of this 

 cutworm points further to recent development of the subterranean habit. 

 Cutworms which enter the soil generally tend either to lose their pigment, 

 like Sidemia devastatrix, or to become indistinctly marked and dully 

 colored. We know of few equally subterranean larvae with such bright 

 colors and distinct markings as dandestina. Agrotis c-nigrum, to which this 

 species is very closely related, exhibits similar but much less distinct 

 markings and duller colors, its curve being typical of cutworms which 

 burrow in the ground. Clandestina is probably one of our "youngest" 

 cutworms, this habit, altho quite well developed, being too young phylo- 

 genetically to be accompanied by a marked shortening of the epicranial 

 stem. 



