Land Snails and Slugs of the Pacific Northwest

Slugs

Slugs The following taxa are those commonly known as slugs, the shells of which are reduced and completely enclosed within the mantle or, if visible, are too small for the animal to withdraw into. Vitrina is usually thought of as a snail, having a shell that covers most of the body, but it is included in the same superfamily as many of the old-world slugs; with its large aperture and body whorl, and small early whorls, the animal is not completely concealed when contracted. Keys to the identification of the slugs begin on page 60, and a diagram of slug morphology appears on that page. Keys to the genera of the superfamily Arionoidea are found beginning on page 281. Keys to the species are presented with the following species accounts to their respective genera. Directory to Taxonomy of the Slugs Superfamily Family Genus Page LiMACOiDEA ViTRiNiDAE Vitrina 268 BOETTGERiLLiDAE Boettgerilla 269 LiMACiDAE Lehmannia 270 Limax 271 AGRiOLiMACiDAE Deroceras 274 PARMACELLOiDEA MiLACiDAE Milax 279 TESTACELLOiDEA TESTACELLiDAE Testacella 280 ARiONOiDEA ARiONiDAE Arion 282 ANADENiDAE Prophysaon 289 Kootenaia 300 Carinacauda 302 Securicauda 303 ARiOLiMACiDAE Ariolimax 305 Gliabates 306 Hesperarion 307 Magnipelta 309 Udosarx 310 Zacoleus 311 BiNNEYiDAE Hemphillia 314 268 LAND SNAILS AND SLUGS OF THE PACIFIC NORTHWEST Superfamily: LImAcoIdEA Many of the members of this family group are old-world slugs introduced into North America. However, one snail, Vitrina, and some of the slug species of Deroceras are native to North America and the Pacific Northwest. Family: VItRINIdAE Genus: Vitrina Vitrina pellucida (müller, 1774) Western Glass-snail Synonym: Vitrina alaskana dall Description: This small, uniquely shaped snail is 6 to 8 (rarely to 10) mm wide by 2+ mm high in about 2½ to 3 whorls. The shell is very thin, transparent, glossy, and light green. The spire is low and narrow, the greatest part of the width being in the body whorl, which increases in size very rapidly. It is imperforate. The aperture is larger than the rest of the shell, wider than high and a little oblique. The protoconch is sculptured with spiral rows of microscopic puncta (dots). At first sight of a living specimen, the transparent, glossy shell blends in with the body and the well-overlapping mantle edge, giving the animal the appearance of a small slug. A fresh, clean shell was so clear that it was barely visible in the photograph, so a soiled shell was used for the above illustration. Similar Species: The unique shell of this snail effectively distinguishes it from all other snails in the Pacific Northwest. Distribution: Vitrina pellucida is widespread from Alaska through British Columbia and the western and Rocky Mountain states, east to South Dakota and south into southern California, Arizona, and New Mexico. It is common under brush on open slopes, under aspen and other hardwood stands, and in riparian areas. In the southern part of its range, it occurs only at high elevations. Vitrina pellucida: Snake River, Asotin Co., WA; width 6-8 mm SPECIES ACCOUNTS: VITRINIDAE, bOETTGERILLIDAE 269 Slugs of the Families BoEttGERILLIdAE, LImAcIdAE, AGRIoLImAcIdAE, mILAcIdAE, and tEStAcELLIdAE Family: BoEttGERILLIdAE Genus: Boettgerilla Boettgerilla pallens Simroth, 1912 Wormslug Description: A small to medium-sized slug, 30 to 60 mm long, pale gray or yellowish; darker blue-gray dorsally. Pneumostome in the third quarter back in the right side of the mantle. A distinct dorsal keel runs from the posterior edge of the mantle to the end of the tail. The sole is yellow, the mucus clear. The body is narrow and sinuous (worm-like) when extended and crawling. Similar Species: The most similar species within our area is the Ryan Lake slug, Zacoleus leonardi, which is bluish-white and keeled the length of the tail. It can be distinguished from Boettgerilla by the position of its pneumostome, which is well back in the mantle, and a secondary pore even farther back, as in Zacoleus idahoensis, to which it appears closely related. Distribution: Boettgerilla pallens is native to southeastern Europe but is rapidly spreading across the continent and through the British Isles. It has been reported on Vancouver Island, British Columbia, by Reise et al. (2000) and Forsyth (2004), but to date it has not been documented from the United States. Boetgerilla pallens: Vancouver island, British Columbia (Kristiina Ovaska photo) 270 LAND SNAILS AND SLUGS OF THE PACIFIC NORTHWEST Family: LImAcIdAE Genera: Limax and Lehmannia Larger slugs, 50 to 200 mm long. Tail tapers gently to...