All you ever wanted to know about Patera appressa

Well almost …

Last month, Mike Oldham, Fred Schueler, and I published our paper on Patera appressa in Ontario. This species had been on our radar for some time. Fred discovered it for the first time in Ontario (and Canada) in the spring of 1994. Since that time, all of us have gone back to sites; I was there last September (2014).

Patera appressa

Patera appressa from along the Trent River, Trenton, City of Quinte West, Hastings County, Ontario, Canada; NBM 009026; maximum diameter (width), 14.3 mm.

The main purpose of our paper was to explain why we think that Patera apressa is introduced and not autochthonous (native) to the area, Ontario, and Canada. For although we included it in our book (see here), we didn’t have the space to get into detail. We also hadn’t deeply investigated the “history” of this species — who found it when, exactly where in Trenton, and how many individuals were seen. The process of tracking down all this was complicated. Wayne Grimm had played a role and we had difficulty making sense of incomplete records and missing specimens.

While we concluded that there appears to be declining numbers of live and fresh-dead shells at the sites, further fieldwork would be worthwhile.

Forsyth, R. G., M. J. Oldham, & F. W. Schueler. 2015. Patera appressa (Say, 1821), an introduced land snail in Ontario, Canada (Mollusca: Gastropoda: Polygyridae). Check List 11(2): 1583. doi: