More Big Bluet damselflies (Enallagma durum) were spotted in July 2016 during two photowalks along the Potomac River at Dyke Marsh Wildlife Preserve (DMWP).
More males
These individuals are males, as indicated by their blue and black coloration and by their terminal appendages.
Mating pair
The mating pair of Big Bluet damselflies shown in the following photograph is “in wheel,” in which the male uses “claspers” (terminal appendages) at the end of his abdomen to hold the female by her neck/thorax while they are joined at their abdomens. The male, blue and black in color, is on top; the female, green and black in color, is on the bottom.
The copulatory, or wheel, position is unique to the Odonata, as is the distant separation of the male’s genital opening and copulatory organs. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 377-378). Princeton University Press. Kindle Edition.
The wheel position is sometimes referred to as “in heart” when damselflies mate. In this case, the heart shape is deformed slightly.
The same pair is “in tandem” a while later: the male is on the right; the female is on the left. The male is engaged in “contact guarding,” in which the male and female fly “in tandem” to egg-laying sites. Contact guarding is used by some species of odonates to prevent aggressive males from hijacking the female.
Look closely at the underside of the female’s abdomen, near the tip. Notice the ovipositor that she uses to insert eggs into vegetation (endophytic oviposition).
It’s helpful to take photos of mating pairs of damselflies, especially “in tandem,” since males and females of the same species can look quite different.
Sidebar: Scientific Classification of Damselflies
The following concise explanation of the scientific classification of damselflies is provided to help the reader understand where the genus Enallagma (American Bluets) fits into the bigger picture of the Order Odonata, Suborder Zygoptera (Damselflies).
There are five families of damselflies in the United States of America, although only three families occur in the mid-Atlantic USA: Broad-winged damselflies; Narrow-winged damselflies (a.k.a., Pond Damselflies); and Spreadwing damselflies.
Family Calopterygidae is comprised of two genera.
Family Coenagrionidae is comprised of 14 genera. Three genera are common in Northern Virginia: Argia (Dancers); Enallagma (American Bluets); and Ischnura (Forktails).
- Argia (e.g., Blue-fronted Dancer, Blue-tipped Dancer, Variable Dancer)
- Enallagma (e.g., Big Bluet, Familiar Bluet, Orange Bluet, Stream Bluet)
- Ischnura (e.g., Eastern Forktail, Fragile Forktail, Rambur’s Forktail)
Family Lestidae is comprised of two genera.
- Archilestes (e.g., Great Spreadwing)
- Lestes (e.g., Slender Spreadwing, Southern Spreadwing, Swamp Spreadwing)
There are relatively few genera of Broad-winged Damselflies and Spreadwing Damselflies. In contrast, there are many more genera and species of Narrow-winged Damselflies — more species, including many that look similar, makes this family the most challenging to learn!
Related Resources: Excellent digital scans created by Gayle and Jeanelle Strickland. Click on the button labeled “Download file” in order to view full-size version of the graphics.
Copyright © 2016 Walter Sanford. All rights reserved.
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