There are 62 species of Sympetrum worldwide, and 14 in North America. More or less. Species limits are not well defined for some, hence the difficulty in telling apart some species in the field, or even in the hand. Many species vary geographically. Generally, field marks to look for (especially in confusing species) include the pattern of black on the abdomen, color of the face, and color of the legs. When immature, meadowhawks are largely yellowish-orange, with facial colors in particular not fully developed or helpful.
Here are the species that most commonly cause confusion in North America:
- Sympetrum rubicundulum (Ruby, hereafter RUME)
- S. internum (Cherry-faced, CFME)
- S. obtrusum (White-faced, WFME)
- S. janae (Jane's Meadowhawk, JAME)
Mature WFME have white faces, which should be helpful. Until maturity, though, eastern forms cannot be distinguished from CFME in the field. Even in the hand, immature female CFME and WFME cannot be separated in the east, as their subgenital plates are essentially identical (in the west, the subgenital plate of CFME is quite different from eastern forms!). WFME also hybridize, or have intermediate forms, with both RUME and CFME.
Sympetrum semicinctum, the Band-winged Meadowhawk (BWME), found across most of the central and northern U.S. It varies geographically, causing problems in some areas. In the east, identification is usually pretty straightforward as the wings are amber-colored to the nodus. But beware some RUME west of Ohio may have amber wing bases, sometimes as extensive as BWME.
S. occidentatale, but genetic work indicates that S. occidentatale is not a valid species.
Likewise, in Europe, there are no good morphological characteristics to distinguish Common Darter (S. striolatum) and Highland Darter (S. nigrescens), and genetic work was also unhelpful.
The bottom line: beware of the little red odes of summer.
Caitling, P. M. 2007. Variation of hind-wing colour and length in Sympetrum internum (Odonata: Libellulidae) from the Canadian prairie provinces Canadian Entomologist 139(6):872-880. (Abstract)
Canning, R. A., and R. W. Garrison. 1991. Sympetrum signiferum, a new species of dragonfly (Odonata: Libellulidae) from western Mexico and Arizona. Annals Ent. Soc. America. 84:474-479.
Carle, F.L. 1993. Sympetrum janae spec. nov. from eastern North America, with a key to nearctic Sympeturm (Anisoptera: Libellulidae). Odonatalogica 22(1):1-16.
Donnelly, T.W., 1991, Current problems in Sympetrum and Libellula (a.k.a. Plathemis). Argia 3(4): 8-12.
Parkes, K. A., W. Amos, N. W. Moore, J. I. Hoffman, and J. Moore. 2009. Population structure and speciation in the dragonfly Sympetrum striolatum/nigrescens (Odonata: Libellulidae): An analysis using AFLP markers. European Journal of Entomology 106:179-184. (Abstract)
Pilgrim, E. M., and C. D. Von Dohlen. 2007. Molecular and morphological study of species-level questions within the dragonfly genus Sympetrum (Odonata: Libellulidae). Annals of the Entomological Society of America 100:688-702. (Abstract)
This has nothing to do with taxonomy, hybridization, or identification, but I came across it in my research and had to throw it in because I liked the title:
Horvath, G., P. Malik, G. Kriska, and H. Wildermuth. 2007. Ecological traps for dragonflies in a cemetery: the attraction of Sympetrum species (Odonata: Libellulidae) by horizontally polarizing black gravestones. Freshwater Biology 52: 1700-1709.