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red and black beetle - Bitoma crenata

red and black beetle - Bitoma crenata
Harvard, Worcester County, Massachusetts, USA
April 30, 2005
Size: ~3mm
Is this a bark beetle or something similar? Found under tight bark.

Images of this individual: tag all
red and black beetle - Bitoma crenata red and black beetle - Bitoma crenata

Bitoma crenata
This one is clearly B. crenata. Tom's long-ago query as to how to separate B. crenata and B. quadriguttata finally led to something.

B. crenata - ninth segment of antennae clearly wider than eighth (a larger species, 2.6-3.5 mm)
B. quadriguttata - eighth and ninth segments about same width (a smaller species, 1.7-2.8 mm). Both species are present in our collection, and they are easy to tell apart.

In Karl Stephan's revision (1989) he comments that B. quadriguttata is extremely common and ranges from New Hampshire to Florida and Texas. B. crenata was introduced from Europe and was spreading from southern Ontario and western New York. To my great surprise, ALL of our specimens in the UNH are B. crenata, and we have absolutely NO B. quadriguttata. Either they have been competitively replaced, or some/all of Karl's New England records are wrong. Karl was a very careful worker, so I'm not quite sure what the story is.

Now that I know the difference
I'll keep my eyes peeled (loupe assisted) for a quadriguttata.

Cylindrical bark beetle?
The ridges on the pronotum (top of thorax) suggest the family Colydiidae to me. Nice image that should eventually lead to a genus.

Colydiidae sounds good, Eric. Check out the images of Bitoma crenata here - it looks just about right to me. According to the checklist here only two species of Bitoma occur in Ontario (see my previous comment - it looks like this is the same species I photographed), and one of them is B. crenata (introduced). These look close enough to be the right genus, at least.

Similar to mine
This look pretty similar to one I just submitted (1). Hopefully we can get an ID for these.

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