Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
Plathemis Hagen, 1861 (Libellulidae) (Whitetails) of Michigan - Identification
Plathemis is a genus of two species, of which one - P. lydia (Drury, 1773) - is widespread in North America and is found throughout Michigan. Nymphs are dark green to brown, stout, robust and often covered in detritus due to its sprawling habit in softer substrates. They inhabit both ponds and sheltered inlets of lakes as well as pool segments of streams. In Michigan adults emerge generally in very late May through the first half of June. The body form of the adult is stout, with a somewhat dorsoventrally compressed abdomen. Males are striking in their appearance with wings having one dark brownish-black basal marking and another more distal black band on an otherwise hyaline wing, and a bright white abdomen (may fade with age). Females wings have three brownish marks: a narrow basal mark extending from the wing attachment to the triangle, an incomplete midwing band that is almost triangular in shape, and a complete band covering the wingtip. Females somewhat resemble Libellula pulchella, but can be differentiated from that species by the yellowish zigzag pattern on the abdomen. Nymphs are distinguished from other species of Libellula by the curved, crenated premental front margin that have small setae within the notches, and from Ladona julia by the the presence of more than 9 premental dorsal setae (3 or less in Ladona), the lack of mid-dorsal spines on abdomenal segments 7 and 8 (present in Ladona julia), and the abdomen with dark, longitudinal stripes (absent in Ladona julia). Levine (1957) gives a minutely-detailed morphological description of the larva and a key to differentiate between the two species of Plathemis (P. lydia and P. subornata).
The taxonomic placement of Plathemis with regards to Libellula and Ladona (and other closely related taxa) is discussed on the page for Libellula.
Life cycle is generally univoltime (Wissinger 1988). One specimen collected by Ed Kormondy in the Maple River, Emmet Co. in the northern LP on 20 August 1953, has well-developed wing pads, suggesting either another population with late emergence, or nymphs may exhibit developmental diapause until emergence the following year.
Taxonomic references: Needham et al. 2010, Paulson 2011, Walker and Corbet 1975
Page created: July 17, 1998 - Last updated: February 17, 2017 (EB)