Spangled Skimmer dragonflies (Libellula cyanea) are easy to recognize because of their distinctive black-and-white pterostigmata, located on the leading edge of all four wings, toward the wing tips. Spangled Skimmers display sexual dimorphism, that is, coloration is different for mature males and females.
Immature male- and mature female Spangled Skimmers are nearly identical in appearance except for their terminal appendages. Another useful field marker: females have broad dark wing tips; males, not so much.
The following gallery features an immature male spotted on 25 May 2014 near a vernal pool far from the central wetland area at Huntley Meadows Park.
The next gallery shows a female spotted on 06 June 2014 along the gravel road between the Hike-Bike Trail and the new observation platform located on the southwestern side of the central wetland area.
Notice the dark spots on the female’s wing tips. A side view of the female (see Photo 6) shows another observable difference between male- and female Spangled Skimmers: Females have a pair of flanges beneath their eighth abdominal segment (segments are numbered from front to back) that are used to scoop and hold a few drops of water during oviposition, hence the family name “Skimmer.” Photo 3 (above) shows a partial side view of the immature male. Look underneath his eighth abdominal segment … no flanges!
The following slideshow features the two photos in this post that show the difference between the terminal appendages of male- and female Spangled Skimmer dragonflies most clearly. All male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”) and a lower unpaired epiproct (“inferior appendage”). Female dragonflies have a pair of cerci (superior appendages) that have little or no function. Can you see the difference between their terminal appendages?
Copyright © 2014 Walter Sanford. All rights reserved.
Tags: cerci, claspers, epiproct, female, Huntley Meadows Park, immature male, Libellula cyanea, pterostigma, sexual dimorphism, Skimmer Family, Spangled Skimmer dragonfly, terminal appendages, wildlife photography
walter sanford's photoblog 
Leave a Reply