Cepaea nemoralis (Gastropoda. Helicidae) — Whitson 



87 



(Arnold 1968, 1969; Jones et al. 1977). For 

 example, even in regions with generally warm 

 climates, brown shells may be favored in cer- 

 tain cool, shady microhabitats, because brown 

 individuals absorb heat faster than pale indi- 

 viduals and can thus become active more 

 quickly (Jones et al. 1977). 



Early workers observed that wood snails 

 had a tendency to "mimic" their backgrounds, 

 with the shell colors that best blended into the 

 background being the most common (Howe 

 1898). Later workers have shown that visual 

 selection by predators can produce this effect 

 (Currey et al. 1964; Davison 2002; Jones et al. 

 1977). In Great Britain, song thrushes are ef- 

 ficient snail predators, crushing the shells on 

 stones to get to the snail. Birds see in color, 

 and in areas where song thrushes are com- 

 mon, shells which contrast with their back- 

 grounds are preferentially eaten (Currey et al. 

 1964; Jones et al. 1977). Other predators such 

 as mammals and glowworms have also been 

 shown to prefer certain shell morphs over oth- 

 ers (Jones et al. 1977). 



With such a wealth of information on the 

 genetic control of shell color, diversity of nat- 

 ural populations, and factors infiuencing shell 

 morphs, wood snails have become wonderful 

 model systems for study of evolutionary mech- 

 anisms and ecological genetics (Davison 

 2002). These organisms have the added ad- 

 vantage of being common and easy to work 

 with in both the field and the lab. 



ECOLOGICAL IMPACT 



Some authors have expressed concern about 

 the potential impact of non-native snails upon 

 populations of our native species (Cowie and 

 Robinson 2001; Mead 1971). Several years 

 ago, wood snails were introduced to the Stone 

 Lab area of Gibraltar Island (Ohio) via land- 

 scaping activities, and Dr. Michael Hoggarth 

 of Otterbein College has since noted an ap- 

 parent decrease in the numbers of native 

 snails seen there (pers. comm.). This is an is- 

 sue that calls for further study. 



CONCLUSION 



While recent surveys of C. nemoralis pop- 

 ulations in the U.S. are Hmited, it is obvious 

 that this species has become widely estab- 

 fished. Several populations from Kentucky 

 have been noted, and further searching would 



undoubtedly uncover more. Though the spe- 

 cies is apparently not a major agricultural pest, 

 the potential impact of these very successful 

 afiens on our native snail populations should 

 be of concern. However, now that the wood 

 snail has come to stay, its potential for use in 

 the classroom or for ecological genetics stud- 

 ies is an opportunity not to be overlooked. 



ACKNOWLEDGMENTS 



Thanks to Dr. Michael Hoggarth of Otter- 

 bein College in Westerville, Ohio for critiqu- 

 ing this paper; to Merritt Gillilland of Michi- 

 gan State University for advice on finding 

 some of the early literature on Cepaea intro- 

 ductions in the U.S.; to Dr. Debra Pearce, 

 Northern Kentucky University, for aid; and to 

 Dr. John Thieret and the staff of the Lloyd 

 Library in Cincinnati for providing access to a 

 variety of delightful and very vintage malaco- 

 logical works. 



LITERATURE CITED 



Abbott, R. T. 1950. Snail invaders. Nat. Hist. 59(2):80-85. 

 Abbott, R. T. 1989. Compendium of landshells. American 



Malacologists, Melbourne, FL. 

 Arnold, R. 1968. Climatic selection in Cepaea nemoralis 



(L.) in the Pyrenees. Philosoph. Trans. Roy. Soc. Lon- 

 don, Ser. B, Biol. Sci. 253:549-593. 

 Arnold, R. 1969. The effects of selection by climate on 



the land-snail Cepaea nemoralis. Evolution 23:370-378. 

 Barber, M. D. 1918. Helix nemoralis in Knoxville, Tenn. 



The Nautilus 31:107. 

 Binney, W. G., and T. Bland. 1869. Land and fresh water 



shells of North America, Vol. 1. Smithsonian Misc. Coll. 



194. 



Branson, B. A., and D. L. Batch. 1969. Notes on exotic 

 moUusks in Kentucky. The Nautilus 82:102-106. 



Brooke, J. M. (Mrs.) 1897. The colony of Helix nemoralis 

 at Lexington, Va. The Nautilus 10:142-143. 



Brussard, P. F. 1975. Geographic variation in North Amer- 

 ican colonies of Cepaea nemoralis. Evolution 29:402- 

 410. 



Burch, J. B. 1962. How to know the eastern land snails. 

 W. C. Brown Co., Dubuque, lA. 



Cain, A. J., P M. Sheppard, F R. S. King, and J. M. B. 

 King. 1968. Studies on Cepaea: the genetics of some 

 morphs and varieties of Cepaea nemoralis (L.). Philo- 

 soph. Trans. Roy. Soc. London, Ser. B, Biol. Sci. 253: 

 383-396. 



Cowie, R. H., and D. G. Robinson. 2001. Pathways of 

 introduction of nonindigenous land and freshwater 

 snails and slugs. California Department of Food and 

 Agriculture, Plant Pest Diagnostic Center, 2001 Inva- 

 sive Mollusc Conference, Sacramento, CA. Accessed at 



