Some Challenging Questions in New England Odonata

Nick Donnelly



In Enallagma, two species appear to be intergrading widely: Northern Bluet (E. cyathigerum) and Vernal Bluet (E. vernale). In the Northeastern part of the US and adjacent Canada ( Michigan to Nova Scotia and south to Pennsylvania , cyathigerum is almost invariably a bog species, avoiding habitats with a significant fish population. E. vernale, on the other hand, is found in medium-sized rivers and lakes, commonly with abundant fish. However, both species wander from their preferred habitats and evidently intergrade - that is, hybridize, but produce fertile offspring. Typically, specimens of cyathigerum taken together at a single time range morphologically between the two end members. Enallagma vernale is scarcer, but populations again show morphological variation. In the remainder of its broad range (west from Wisconsin to the west coast and north to Alaska ) cyathigerum inhabits almost all aquatic habitats. How did it become restricted to fishless habitats in the northeast? We need more observations, especially occurrences in Massachusetts , where it has been reported far less than in New York .

The genus Tetragoneuria provides another, very different, challenge. In easternmost Massachusetts the common species seems to be semiaquea, but it has unmarked wings and is easily confused with cynosura. From Long Island southward semiaquea has broad wing markings, except that in New Jersey a minority have deeply reduced maculation. The challenge is to find if the two species co-occur in Massachusetts , and, if so, do they show differences in behavior and/or habitat.


Biography: Nick Donnelly has been studying odonates across North American and the world for over half a century, and is one of the world’s pre-eminent odonatologists. He was one of the founding members of the Dragonfly Society of the Americas and edits their newsletter, Argia. He has published scores of papers about odonates worldwide, and is currently working on a guide to North American Odonata.


Contact Info: T. W. Donnelly, 2091 Partridge Lane , Binghamton , NY 13903 . Email: