Thursday, June 9, 2011

Just a Photo: A Table for Eight, Please?

I figured readers would enjoy this photo. Here we have four pairs of Vivid Dancers (Argia vivida), all ovipositing in tandem on the same sprig of emergent vegetation at Gold Lake, Oregon. I can just imagine the males discussing the issues of the day over cold brews while the females are busy depositing their eggs. It’s not unusual to find multiple pairs of a species ovipositing in close proximity like this, but I don’t think I’ve ever seen a group “seated” so nicely.

On a more technical note, what you’re seeing is an instance of contact guarding—the mated male remains in tandem to the female while she’s depositing eggs in order to prevent other males from coming along and removing or displacing his sperm (it’s safe to assume that each of these pairs copulated before they all found this great piece of real estate). Contact guarding is common among the damselflies (coenagrionids and lestids, anyway), but is more limited among the dragonflies where it is chiefly performed by some libellulids (skimmers), as well as the Common Green Darner (Anax junius).

3 comments:

  1. Wonderful Jim! This is such a better shot than the one I use in my programs to talk about this, but I call it 'sentinel guarding' - but it's just another term for the same thing I guess. I have one blurry shot where the guys are having a fisticuffs battle while the females oviposit - such a hoot!

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  2. @Kathy Biggs Thanks, Kathy. I use the term "sentinel" in specific cases when the male is in an erect position while in tandem, only holding onto the female with his abdominal appendages and not grasping anything with its legs. Since the males in this photo are holding on to vegetation in this case, I wouldn't apply the term "sentinel".

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