Gnorimosphaeroma oregonensis

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Oregon pillbug:
Oregon pillbug (Gnorimosphaeroma oregonensis): This is basically a roly-poly by the sea. It is most often found by turning over pieces of wood in estuaries in the higher intertidal. This species has the ability to roll into a ball, and to withstand long exposures to freshwater intrusion. Rock Louse (Ligia pallasi) is much larger and flatter, and runs fast. A look-alike species is Brackish Water Pillbug (Gnorimosphaeroma insulare), which looks just the same as the Oregon pillbug, except that it is even more freshwater-tolerant, and when inspected closely, the segments go as follow: from rear to front, the rear-most segment is broad, and is followed by a segment with two creases and three extensions. That creased segment is the important one; in G.oregonensis all three extensions reach out to the edges, whereas in G. insulare the rear-most one tapers off just before reaching the edges.

If you want to dabble in isopod taxonomy, there is a third species! Its name is Gnorimosphaeroma noblei. It may or may not be found in our area, and its antennae meet directly, without a rostrum in between them.

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