470 Bulletin American Museum of Natural History [Vol. LITI 
mollusks are comparatively free from the attacks of other predaceous 
enemies, since they are well protected either by a calcareous shell or by 
an abundant slimy secretion of the skin. In many cases, too, the peculiar 
coloration and the arrangement of the markings upon the shell un- 
doubtedly add to the difficulty of locating them in their natural environ- 
ment, even if the pattern appears to be particularly showy in collections.* 
The secretive habits of most snails and slugs also contribute to their 
personal safety; many species are strictly nocturnal or crawl about 
during rainstorms only, when most of their potential enemies are 1n- 
active.’ 
Among arthropods, certain carnivorous beetles appear to be quite 
efficient enemies of snails. Récluz, in Southern France, observed Staphy- 
linus olens Miiller attacking Helix ericetorum, the snail being slowly 
killed by repeated bites. Certain Carabide do likewise and the 
Cychrine in particular appear to specialize in snails, their long, snout- 
like head allowing these beetles to reach far into the coils of the 
spire. The family Thelephoride contains many species whose larvee 
feed exclusively upon snails. Lucas observed in Algeria how the larva of 
Drilus mauritanicus Lucas manages to enter the shell of live Cyclostoma, 
in spite of the operculum with which the aperture can be tightly 
closed. The larva patiently awaits the moment when the snail brings the 
operculum ajar, then suddenly wedges its mandibles between the oper- 
culum and the edge of the aperture, and attacks the muscle which fixes 
the’ operculum to the foot, so that the aperture can no longer be locked. 
It then leisurely devours the contents of the shell. The common Euro- 
pean Drilus flavescens (Rossi) and the rarer D. concolor Ahrens have 
similar habits: their larvee destroy large quantities of Helix nemoralis, H. 
ericetorum, and many other Helicide.* Snail-eating habits are common 
1The vexed question of the efficacity of protective coloration in nature cannot be discussed here. 
So far as terrestrial mollusks is concerned, it is briefly treated by A. H. Cooke, 1895, ‘Molluscs’ (Cam- 
bridge Natural History, III), pp. 66- 74. Seealso Taylor, J. W., 1894-1900. ‘Monograph Land Freshw. 
Moll. Brit. Isl., Struct. Gen. Vol.,’ (Leeds), pp. 327-332. 
2See an interesting, though ancient, account by Petit de la Saussaye, S. 1852. ‘Des ennemis des 
ropae ou des causes qui s’opposent 4 leur trop grande multiplication.’ Journ. de Conchyl., III, pp. 
The junior author recently published an account of the arthropod enemies of mollusks, to 
which the reader may be referred for more details and a complete bibliography. See Bequaert, 
J., 1925. ‘The arthropod enemies of mollusks, with description of a new dipterous parasite from 
Brazil. Journ. of Parasitology, XI, pp. 201-212. (Reprinted with additions in 1926, ‘Medical 
Report of the Hamilton Rice Seventh Hixpedition to the Sa in conjunction with the Depart- 
ment of Tropical Medicine of Harvard University,’ pp. 292-303.) 
SLucas, H. 1842. ‘Sur une nouvelle espéce du genre Drilus qui habite le nord de I’ Afrique.’ Cy. A. 
Ac. Sci. Paris, XV, pp. 1187-1189. 
4Mielzinsky, I. 1824. ‘Mémoire sur une larve qui dévore les Helix nemoralis et sur l’insecte auquel 
elle donne naissance.’ Ann. Sc. Nat., I, pp. 67-77, Pl. viz. 
Crawshay, L. R. 1908. ‘On the life-history of Drilus flavescens Rossi.’ Trans. Ent. Soc. London, 
pp. 39-51, Pls. 1-11. 
Rosenberg, E.C. 1909. ‘Drilus concolor Ahr.: Hunnens Forvandling i Skallen af Helix hortensis,’ 
Entom. Meddel., Kopenhagen, (2) IIT, pp. 227-240, Pls. rv—v. 
Schmitz, H. 1909. ‘Zur Biologie von Drilus flavescens Fourcr.,’ Bericht. Nederl. Ent. Ver., IT, 
pp. 301-305. 
