These small snails are Zonitoides arboreus, commonly called the “Quick Gloss Snail” or “Orchid Snail.” This species is found in urban gardens and is native to North America. So, it looks like this is a California native living in our NHM Nature Garden! On Feb. 3, 2015, Jennifer Hudson, a visitor to the NHM with her two daughters found these specimens under the rocks and among the leaf litter in the Nature Garden.
Interestingly, while Zonitoides arboreus is native to most of North America, it has become an invasive pest in Hawaii, where it eats the roots of orchids in commercial orchid gardens. Morphologically, this species can be distinguished from species in the genus Oxychilus, by its smaller shell with obvious growth lines, higher spire, and more deeply impressed suture. See below:
Update: these snails initially proved difficult for me to identify, but I’m pretty sure I’ve gotten the hang of it now. On 1/14/2015, three volunteers (Anna Chilingarian, Scott Westerson, and Amy Aldous) and I ventured just outside the NHM building to the Nature Garden looking for snails. Among the leaf litter Scott found
(what I thought was) a lovely Oxychilus, commonly called the glass snail. Oxychilus sp. is one of three Oxychilus species introduced to Los Angeles. This is the first record of this snail in the Nature Garden. Its native range is Europe, North Africa, and parts of the Middle East, but it is now found throughout much of the United States and the world because of accidental introduction, possibly from the plant trade. 1/30/2015: because of some comments by keen observers on iNaturalist, I have re-visited my initial species identification, and consulted with snail experts Lindsey Groves and Phil Liff-Grieff, who confirmed the identity of this snail as Oxychilus sp.
To explain my initial misidentification, I’ll add that land snails can be tricky to identify, and the differences between species in the genera Oxychilus and Zonitoides, in particular, are relatively subtle and take very careful observation to notice. One big difference is size. Oxychilus species are typically bigger than species of Zonitoides. This specimen’s shell is 1 cm in diameter. Also its spire is relatively flat with an impressed spire, but not as deeply impressed as in Zonitoides. More on Zonitoides in the next post!