Terrestrial Pulmonate Gastropods Found At A Locality In Southern California 

Terrestrial-pulmonate gastropods have the ability to breathe air. They represent an informal taxonomic group that includes terrestrial (land) and freshwater families, and even a few marine families.

Over many years, I have found several different kinds of terrestrial pulmonates (those with shells and some without) in my yard, in northern Los Angeles County, southern California. Even though these kinds of gastropods are not in my field of expertise, I tried to identify them, with considerable help from my friends at the Malacology Department of the Natural History Museum of Los Angeles County. 

The result of my efforts, after many years of “collecting” right in own yard, is that they are four families present: four genera, and four species. Also, I was surprised to learn that these taxa originated in Europe and were later introduced into the USA. Also, they were all named between 1758 and 1822.

Shelled Pulmonates

Rumina decollata (Linnaeus, 1758)

Common name: decollate snail

Family: Achtinidae

Distribution: native to Europe and the Mediterranean region; introduced to the USA (California, Arizona, Florida, Georgia, No. Carolina, So. Carolina, and Texas) and to Cuba, Mexico, and Bermuda.

Remarks: They remain hidden in debris unless it rains, then they crawl about over sidewalks and driveways. They are voracious predators and eat any other snails they encounter, especially Cornu aspersum.

Images: (in order of appearance): Juvenile specimen (one view) with its non-truncated shell (9.5 mm height). Adult specimen (four views) with its truncated shell 31.5 mm height; front view, back view, tilted side view, and top view.

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Cornu apserum (O.F. Müller, 1774)

Common name: brown garden snail

Family: Helicidae

Distribution: native to Europe, North Africa; introduced to many parts of the USA  (including California) and to South America.

Remarks: These snails are vegetarians and can be very destructive if they find their way into your garden. This species is the most common terrestrial snail in Los Angeles County, southern California. They were common in my garden, until Rumina decollata showed up; now, Cornu aspersum is very rare there. 

Images: Adult specimen, 27.9 mm height (3 views): front, back, and right side, showing outer lip edge.

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Oxychilus sp. 

Common name: glass snail

Family: Oxychilidae

Distribution: native to Europe, North Africa, and parts of the Middle East; introduced to many parts of the USA (including California). 

Remarks: The common name refers to being able to see “through” their somewhat transparent shell. These snails prefer humid places under leaves and stones. This snail is one of two similar species; it is probably O. draparnaldi (Beck, 1837). Positive identification would need anatomical studies.

Images: Adult specimen, 4.2 mm height, 11.5 mm width, 3 views: front, top, and bottom.

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Slug Pulmonate

Ambioglolimax valentianus (Férussac, 1822) or Ambiogloimax nyctelin (Bourguignat, 1861)

Common name: Three-band garden snail 

Family: Limacidae

Distribution: native to Europe (Spain and Portugal); introduced to China, Japan, and USA (including California, Oregon, and Washington).

Remarks: One of two very similar species. Positive identification requires internal anatomical studies. This genus has an internal shell (small and flat).

Image: Largest individual approximately 35 mm length.

ADDITIONAL REMARKS:

Europe is the origin for the majority of the many of the non-native terrestrial gastropods found in the world. Their distributions are constantly changing and basically becoming more widespread. If you are interested in the details, please see the following (free) pdf:

Gladstone et al. (2020). Spatiotemporal patterns of non-native terrestrial gastropods in the contiguous United States. NeoBiota 57:133–152.

In my study, I found the following reference useful:

Cōcke, J. 1995. Common land snails of Los Angeles County. Privately published.