Newly Emerged 12-Spotted Skimmer

2020 December 20

We have a small decorative pond that we built some years ago in our side yard[1]. And on September 1, 2019, Sam and Rosie found this lethargic, pale dragonfly roosting on one of the rocks bordering the pond, and brought it in to show me.


The wings were clearly not fully stiffened yet, and it had obviously just come out of the pond and shed its nymphal skin. So they took me out to show me where they found it, and right there we found this recently-molted dragonfly nymph shell.


Even though dragonflies don’t have a pupal stage, they nevertheless undergo a big change in body shape on that last molt, with the abdomen elongating markedly, and a transition from water-breathing to air-breathing. Those white strands in the shell used to be the linings of the breathing spiracles, which pulled out so that the adult could draw air into them.


The head also changes shape a lot. The nymph has relatively small eyes, compared to the enormous eyes of the adult.


Most insects are pale after they first molt, gradually darkening as their new exoskeleton hardens. So, we placed it on a stump near the pond, and I got a series of pictures of it gradually darkening starting at 8:54 AM:


While it had originally been perching with its wings flat, by 9:10 AM it had folded them back up vertically, which is not a typical pose for a dragonfly. It hadn’t darkened noticeably by this time.


By 9:31 AM, there was a dark spot starting to be visible at the base of the wings, where they join the body.


Half an hour later, at 10:01 AM, there started to be hints of additional large dark spots on the wings, although they were still pretty pale.


At this point, we took a break for lunch, and came back to it two hours later at 12:12 PM. This was long enough for it to reach full adult coloration, with very distinct black spots on its wings, a bright yellow stripe running down the abdomen, and two additional yellow stripes on either side of the thorax.


This is good enough for an ID, especially since it turns out to be a pretty common dragonfly. It is a Twelve-Spotted Skimmer, Libellula pulchella. They are mostly a summer-flying species, although they can clearly emerge as late as September, like this one did. The twelve spots are pretty obvious (3 spots on each of 4 wings), although they are also sometimes called “10-spotted skimmers” because some people think that the spots at the base of the wings look like there is just one long spot running from one wing to the other.

[1] The pond is not particularly large (maybe 6 feet by 18 feet, and about 3-4 feet deep), but it is large enough to support a surprising diversity of small animals. It is lined with a rubber sheet, and on top of the sheet there is a layer of cobble-sized stones (between about 2 inches and 8 inches) which give a lot of crevices for things to hide in. It has a recirculating pump and a waterfall, which allows for filtration and aeration of the water. Basically, it is a really big outdoor aquarium. We stocked it with crayfish, who immediately hid under the rocks where they couldn’t be seen, although we do see them come out from time to time. We also had five tiny goldfish that we put in. It turns out the pond is big enough for them to overwinter successfully, so at the moment we have five really quite big goldfish, five or six medium-to-small sized goldfish (some of which have reverted back to the silvery-gray coloration of the ancestral goldfish stock), and a swarm of tiny gold fish that are barely large enough to see. And, of course, there is algae growing in it, and a variety of aquatic insects that eat the algae (or each other), and a number of itinerant frogs. And, obviously, dragonfly nymphs. We don’t actually have to provide any food to the pond, the algae is profuse enough that all the little creatures appear to get plenty to eat.

2 Responses
  1. Tim permalink
    December 21, 2020

    This sounds exactly like a pond I would want to create. Do you have to take any preventative measures to keep out the predators? We have racoons regularly patrolling our property and herons regularly visit farmland near where we live.

  2. December 21, 2020

    So far, we haven’t had any predators come in, although there are racoons and herons about. I think it is partly because the pond is only about 30 feet from the house, and partly because the raccoons haven’t realized what is there. Also, the rocks on the bottom and sides of the pond make a lot of little nooks and crevices where the fish can hide out, even the big ones. When we go out to watch the fish, if we startle them with a sudden movement they vanish into the rocks almost instantly.

    And as far as that goes, I think that if we started getting, say, a Great Blue Heron going fishing in our pond, we’d be tempted to treat the pond as a heron feeder and just keep stocking it.

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