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Photo#1964068
Snout beetle under quartzite - Tournotaris bimaculata

Snout beetle under quartzite - Tournotaris bimaculata
Sevenmile Creek, 8 kilometers northwest of Helena, Lewis and Clark County, Montana, USA
May 2, 2021
Size: 8.1 mm (eye to elytra)
Dark brown, snouted beetle with 2 pale lines running longitudinally along pronotum. Collected from underside of a subangular quartzite rock, ca 10 cm by 25 cm, on level ground among non-native, rhizomatous grasses regrowing from last September's fire, their leaves up to ca 15 cm now. A cool, moist late morning, 41 F with light rain.
Elevation ca 4000 feet. Disturbed, shrubby riparian corridor on stream restoration site within a patchwork of native and non-native grassland.

Attempted to key to genus in Arnett et al. 2002 but kept getting to genera within the Curculioninae that did not match. Suggestions would be much appreciated!

Images of this individual: tag all
Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata Snout beetle under quartzite - Tournotaris bimaculata

Moved
Moved from Tournotaris.

I revisited this beetle with the curculionid key in American Beetles, and this time I was able to follow the key to genus, except that getting to Erirhininae required dissection, so I "cheated" on that key break based on v's earlier identification of this specimen. I have updated a few of the photos here now that I am using a better microscope. Characters for the genus include the funicle with 7 instead of 6 articles; the tibiae lacking spurs near the small tooth at the inner apical angle; and the funicle with distinct setae instead of fine pubescence. I was able to get to species based on Thompson 2005(1). T. bimaculata is distinguished from the other North American species, T. goliath, by the elytral striae indistinct instead of distinct (at least towards the lateral margins), with the interstriae "distinctly granulose" instead of "rugulose or feebly granulose"; bimaculata has regular pronotal punctures, while goliath has unevenly distributed pronotal punctures, with extensive impunctate areas. Thompson writes, "Many specimens of Tournotaris have a pair of pale spots on the elytra, in interstria 3 at the top of the declivity." (This is seen in several BugGuide observations of these species, but not visible in this specimen). "These spots are, however, absent in some specimens of both T. bimaculata and T. ochotica [the latter not in North America]. Whether they are truly absent or merely lost by abrasion is uncertain but the latter seems more likely."

Based on American Beetles, this species is associated with Typha in wetlands. For what it may be worth, the Typha latifolia stand nearest this beetle's rock was 950 meters NW, with grassland (burned the previous September) between the beetle and the cattails. Perhaps it had dispersed that far from the cattails to overwinter?

diff. family, actually

 
Thank you!
.

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