Hawaiia - Gem Snails (Family Zonitidae)
Gem Snails are tiny (~ 2.2 mm diameter) heliciform snails with a wide and shallow umbilicus and a thin-lipped aperture. The nuclear whorl is smooth but the rest of the surface is cross-hatched with fine, irregularly-spaced growth lines and minute spiral striae.
One species has been commonly identified in Indiana - the Minute Gem Snail, Hawaiia minuscula - and a second rarely (and presumed extirpated by NatureServe) – the Southeastern Gem Snail, Hawaiia alachuana.
Hawaiia is one of a group of five genera of tiny snails - Hawaiia (Gem snails), Lucilla (Coil snails), Punctum (Spot snails), and Striatura (Striate snails) – that are superficially similar. Note the characters in the keys. For example, Lucilla is about the same size, but lacks the microsculpture.
Hawaiia minuscula (A. Binney, 1841) with mm scale
Minute Gem
Hawaiia minuscula (A. Binney, 1841)
Characters: Heliciform, simple lip, subglobose to depressed, umbilicate to perforate, ~2 - 2.5 mm. The nuclear whorl is smooth and the rest of the surface is cross-hatched with fine, irregularly-spaced growth lines and minute spiral striae.
Comparisons: Hawaiia minuscula is somewhat smaller and narrower than H. alachuana. See comparison for H. alachuana next and also Dourson (2015) and Hotopp et al. (2013).
Habitat: This species is found in woodlands, among leaf litter and woody debris; elsewhere at times.
Status: found in various areas of the state in suitable habitat.
Southeastern Gem Snail
Hawaiia alachuana (Dall, 1885)
Go to link above or Dourson (2015) for images and comparison to Minute Gem.
Characters: Heliciform, simple lip, subglobose to depressed, umbilicate to perforate, ~2-2.5 mm. The nuclear whorl is smooth and the rest of the surface is cross-hatched with fine, irregularly-spaced growth lines and minute spiral striae.
Comparisons: According to Oesch et al. (2013), this species differs from Hawaiia minuscula in these ways: (1) a wider umbilicus, (2) in basal view, the lip joins body whorl outside the midline of the whorl, and (3) in dorsal view, the body whorl is larger than in H. minuscula. See also link above or Dourson (2015) for images and comparison to Minute Gem.
Habitat: This species is found in woodlands among leaf litter.
Status: rarely identified in the state, found in two counties in the southwest, presumed extirpated by NatureServe. Dourson (2010) gives this species only as fossils in KY but extant in TN, WV, and VA. However, the two collections in Indiana are relatively recent and credible. So, who knows?
