Family Hygromiidae Tryon, 1866

Subfamily Trochulininae Lindholm, 1927

Tribe Trochulini Lindholm, 1927

Genus Trochulus Chemnitz, 1786

  • Trochulus Chemnitz 1786: 52; type species by monotypy (ICZN 2004 Opinion 2079): Helix hispida Linnaeus, 1758.
  • Trichia Hartmann 1840 (1840–1844): xiii, footnote; type species by subsequent designation (Herrmannsen 1849 (1846–1852), ICZN 2004 Opinion 2079): Helix hispida Linnaeus, 1758; non Trichia De Haan, 1839.

This is a European group of 22 species, with the greatest diversity in the Alps and Carpathians (Proćków 2009). Most of these 22 species are narrow-range endemics; only Trochulus hispidus, and to a lesser extent T. striolatus, are widely distributed in Europe (Proćków 2009). Both species have synanthropic tendencies and are introduced to Canada.

This genus is better known as Trichia, but a ruling by the ICZN (2004) has resulted in replacing Trichia Hartmann, 1840, with Trochulus to remove homonymy with Trichia de Haan, 1839 (Crustacea: Brachyura).

Trochulus is sometimes used in a broader sense to include the subgenera Petasina, and Edentiella (e.g., Schileyko 2006), while other authors have felt that subgenera are unwarranted and combined these taxa as synonyms (e.g., Proćków 2009). Most often, Trochulus, Petasina, and Edentiella are treated as full genera (e.g., Kerney et al. 1983). Both species in Canada belong to the nominotypical subgenus.

Etymology. Greek: diminutive of trochos, a wheel. Masculine.

Trochulus hispidus (Linnaeus, 1758)
Trochulus striolatus (C. Pfeiffer, 1828)

Key to species of Trochulus in Canada

a         Periostracal hairs persisting in adult shells. Periphery more-or-less rounded. Shell width to ca 7–9 mm — T. hispidus

b         Periostracal hairs absent in adults. Periphery distinctly, obtusely angular. Shell width to ca 10–11 mm — T. striolatus