Bug of the Month: Spreadwing Damselfly
By Terry Morse
You've probably heard that the way to tell damselflies from dragonflies is that dragonflies hold their wings out to the side when resting, while damselflies hold their wings up over their backs. There are a few exceptions to this rule: Newly emerged dragonflies hold their wings above their backs until the wings are fully expanded and have begun to harden; when damselflies land on a perch, they hold their wings out to the side until fully settled, then fold them up over the back; and Spreadwing damselflies (Family Lestidae).
In general, damselflies appear more delicate than dragonflies because of their slender build. The two suborders overlap in length, however, with dragonflies ranging from ¾-5" and damselflies generally 1-2" long.
The spreadwing damselfly I have identified locally is Archilestes californica, the California Spreadwing. At 2" long, it is larger than many of the dragonflies you might see. If you look carefully, though, you can tell it is a damselfly by the very slender abdomen, the eyes widely separated on the top of the head, and the stalked wings, which start out slender near the body then expand; the wings of dragonflies are quite broad where they join the body.
Archilestes californica, though not flashy like many other dragonflies and damselflies, is subtly attractive. It is brown with black stripes on the top and side of the thorax (“chest”). The dark abdomen has fine pale rings between segments. The eyes, in contrast, are strikingly blue.
Archilestes is found in autumn near still water. I have seen them most often at Big Creek Reservoir in Newport, around Blattner Creek (about 1.5 miles along the reservoir road on the left), and at Merganser Pond (my own name for it), which is about ½ mile further in on the left. Watch for them perched on trees and shrubs, from which they fly short distances after prey. If you are lucky, you may see a male and female in the “wheel” mating position, or ovipositing in tandem, the male grasping the female behind her head with his abdominal claspers as she lays eggs in the stems of willows and alders above the water with her sharp ovipositor.
If you are unable to find them (and I'm not sure how much longer they will be around, now that the rains have started), come to the next Yaquina Birders & Naturalists meeting, where I will show slides of them and other insects.
© Terry Morse
Revised 17 May 2004
Note: A recent genetic analysis (Saux et al., 2003) suggests that the spreadwing damselflies (family Lestidae) are actually more closely related to dragonflies (Odonata: Anisoptera) than to damselflies (Odonata: Zygoptera). It will be interesting to see whether future studies bear this out.
Saux, Corrie, Chris Simon, and Greg S. Spicer. 2003. “Phylogeny of the Dragonfly and Damselfly Order Odonata as Inferred by Mitochondrial 12S Ribosomal RNA Sequences.” Annals of the Entomological Society of America 96(6): 693-699.