20 May 2021

The mystery of baskettails

Since we are on the cusp of the dragonfly season here in southern Michigan, a quick note regarding the problem with Epitheca baskettails is timely. 
As it turns out, "common" baskettails in southern Michigan (and perhaps beyond, it's unknown until more are collected and examined) are not identifiable from photos, and often not in the hand. 
The Common Basketail (Epitheca cynosura) hybridizes with Slender Baskettails (Epitheca costalis, which used to be called Stripe-winged Baskettail), but northern populations show much variability in the amount of brown at the base of the wings, as do E. cynosura in this region. We've collected a lot of baskettails around here, and the majority of them are intermediate forms, as diagnosed by Nick Donnelly from NY who works on several cryptic/hybridizing/new species complexes. This probably indicates that the two species are hybrids and produce fertile offspring and, in turn, backcrosses.

The New Jersey Odes website, though inactive, has a nice comparison of Common versus Slender, while acknowledging that field identification is iffy, and the Minnesota Dragonfly website has some nice comparisons of Common, Spiny (E. spinigera) and Beaverpond (E. canis).
Other strange Epitheca's can be found. Here is a post we did (with a link to a short paper we wrote) on a Common Baskettail with extensive dark wing tips.
There is so much to understand regarding the status and distribution of this species complex in Michigan. More specimens are needed, especially across southern Michigan, for future researchers to go examine so that these mysteries can be unraveled.

Further reading:

Donnelly, N. [T. W.] 2001. Taxonomic problems with North American Odonate species -- a last appeal for information. Argia 13(2):5-10.

Donnelly, N. [T. W.] 2003. Problems with Tetragoneuria! Argia 14(4):10-11.

Donnelly, N. [T. W.] 2006. Rediscovery of Intergrade Epitheca in Southern Indiana. Argia 18(2):12-13. Scroll to page 12 and read this brief note -- it sums up the problem in the region nicely!

O'Brien, M. 2004. Epitheca costalis (Stripe-winged Baskettail) in Michigan: Update. Williamsonia 8(3):1-2. (PDF

O'Brien, M. 2005 How to identify Epitheca costalis. Williamsonia 9(1):7-9 (PDF)