Familiar(?) Bluet Damselfly - Enallagma

Moved

… john and jane balaban, 12 July, 2008 - 11:53am

moved

to genus

… Tony-2, 14 April, 2006 - 6:53am

Enallagma ID

Enallagma ebrium does not occur in LA, but we do have E. civile and E. doubledayi which present the same difficulties of separation. We have learned to separate them through binoculars or from a good photo. E. Civile has "top heavy" appendages while on E. doubledayi they are more or less evenly distributed. I note from Ed Lam's images that E. ebrium is also evenly distributed. From your photo I suspect that it is not E. civile. Perhaps your original would show sufficient detail for a positive ID. Images of the appendages of E. civile & E. doubledayi may be seen here , in Album #3, pages 4 & 5. Gayle

… Gayle and Jeanell Strickland, 24 March, 2006 - 10:27am

Closeup of tail end

I posted a 100% crop of the posterior for what it's worth. I'm afraid I don't have any better views.

… Peter Hollinger, 24 March, 2006 - 9:19pm

Enallagma boreale or E. cyathigerum

Your photo is either Enallagma boreale or E. cyathigerum. Actually the info needed was on your original photo. According to Lam, the very large eyespots and a small mushroom-shaped spot on the dorsum of segment 2 limit the ID to one of these two. Your cropped photo provided sufficient information to rule out E. ebrium and E. civile, but not quite enough to separate E. boreale from E. cyathigerum. Jeanell favors E. cyathigerum and I think it is a tossup. If you have access to Damselflies of North America by Westfall & May, or Damselflies of the Northeast by Ed Lam, you might check the shape of the genitalia and see what you think. We have enjoyed the chase! Gayle & Jeanell

… Gayle and Jeanell Strickland, 24 March, 2006 - 11:28pm

civile/ebrium/hageni

Ed Lam's fine book on northeast damselflies says the males of Familiar, Atlantic, Marsh, and Hagen's bluets "are virtually identical and should be separated in the hand." The only shred of good news is that we can probably eliminate Atlantic, since it hasn't been reported from north of Massachusetts.

Lam makes a few tentative distinctions about these various species, but notes that most are not reliable, and he does also provide some discussion of tiny differences in the appendages that would be hard to distinguish in a photograph.

--Stephen

Stephen Cresswell
Buckhannon, WV
www.stephencresswell.com

… Stephen Cresswell, 24 March, 2006 - 3:58am

Probably not hageni

Thanks, Stephen -- I'll move the question mark. E. hageni apparently likes more acidic waters, which I don't think we have in the immediate area. So probably Marsh or Familiar.

… Peter Hollinger, 24 March, 2006 - 7:04am