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water beetle? - Nycteus oviformis

water beetle? - Nycteus oviformis
Randolph, Massachusetts, USA
April 27, 2005
Size: 4mm
found under a board.

Images of this individual: tag all
water beetle? - Nycteus oviformis water beetle? - Nycteus oviformis

Another new family for bugguide!
Excellent, Tom!

Thanks Jim
We wouldn't have nearly as many families and genus without Don's help. Now if a few other specialists in other families would visit bugguide.

Eucinetidae: Nycteus oviformis
Consulting the collection, and looking at size, elytral striae, and color, it looks to be N. oviformis. Not a common species, but fits the image quite well.

I think this is in the family Melandryidae. Did it jump and run actively?

If the family is correct (Melandryidae), then this might be a species of Eustrophinus. I have found them regularly associated with non-gilled fungi, but they are very active, slippery, and hard to capture.

It was a cool day
so it didn't move at all.

I don't think it's one of the
I don't think it's one of the water beetles, which are mostly hairless with small antennae to eliminate drag.

At least I know what they aren't.

other options
The long filamentous antennae are interesting. Usually, little beetles like that have a club or some other modififation. Consider families Scirtidae (AKA Heldidae) or Eucinetidae.

Eucinetidae: Eucinetus sp.
I was just curating our Melandryidae sensu lato, keeping these two images in mind, and there are no northeastern genera that look like this that are this size, while members of Eucinetus do have filiform antennae, and are of this shape. There are some small hopping melandryids that superficially look like this, but their antennae are clavate, and I believe they are in the neighborhood of 2-3 mm (Microscapha clavicornis),
A ventral view would settle the matter quickly, as eucinetids have large metacoxal plates.

Ventral view
I'll go back where I found this one in the spring, to get a ventral shot. Then we'll know for sure. I think you're right, but for now, I'll place these pictures in the beetle guide page, otherwise, I'll have to make a new family page, and I want to be 100% sure it's right. Thanks Donald.