Readers’ wildlife photos

October 24, 2020 • 8:00 am

Thanks to the many readers who have been sending me photos. Keep ’em coming, please!

Today’s set of insect photos come from regular Mark Sturtevant, and I’ve indented his comments and IDs. I find the prey-locating and the drilling abilities of ichneumon wasps (below) almost beyond comprehension.

This is a set of pictures of insects that were taken over a short period of time over a year ago. By chance, they focus on a small number of species.

First up is a young widow skimmer dragonfly (Libellula luctuosa). In many of our local fields they are among the most common dragonflies, emerging in steady waves over most of the summer. As this young male matures, it will become accented with a white waxy bloom on its body and wings.

Next is a picture of one of our largest dragonflies, the spatterdock darner (Rhionaeschna mutata)I can well remember my trepidation when first seeing these swift and powerful fliers, since darner dragonflies can be especially difficult to photograph because many of them just . don’t . land (shakes fist at green darners especially). But spatterdocks can be kind to photographers because they will land after a time, and are even surprisingly tolerant of being approached. This stunning specimen is a mature male.

The next pictures are of another male spatterdock. I was just loading my gear into the car after a long day outdoors, when this one landed nearby while carrying … something. So out came the camera again. One can see that the spatterdock had taken another dragonfly (probably a blue dasher), and it was steadily stuffing the meal down its gaping maw. I was able to get in very close as he was finishing up. What a glutton!

Early last summer I was visiting a new park that was near my work. It was beautiful, featuring a sunny pond that was swarming with dragonflies, a lush meadow filled with wildflowers, and even a wetland area dotted with several dead trees. The dead trees were of timely interest since according to my calendar (one must of course note important insect activities in their calendar), giant ichneumon wasps from the genus Megarhyssa were supposed to be around. So I invested considerable time inspecting the dead trees, since that would be where these insects would be laying eggs. There are two species of these large parasitic wasps around here, but I had not seen one except in passing for several years.

A fellow nature lover saw me with my cameras, and came over to chat. After he had learned that I photograph insects, his next words were “Oh, did you see the giant ichneumons?” I must have looked fairly gob-smacked, but he pointed out the tree, and yes indeed there were giant ichneumons! At least a dozen of the large insects on a single tree. Incredible! The following pictures shows a few of them doing their thing.

Giant ichneumons are parasitic wasps, and females use their extraordinarily long ovipositor to drill into dead wood where they target the larva of another wasp known as the horntail. The first two pictures show one of the species, Megarhyssa macrurus. The raised ovipositor is already drilled a couple inches into the wood. At an early stage of this process, the base of the drill becomes partly wrapped with intersegmental membrane, as shown in the 2nd picture. Amazingly, over a period of several minutes the entire ovipositor will be worked into solid wood. She is able to somehow pinpoint a horntail larva and then thread an egg down her ovipositor to the prey deep in the tree. The link includes a film that shows the drilling process.

Among the many giant ichneumons on the tree were several examples of both species. The other local species, M. atrata, is shown next. This one has drilled almost all the way into the wood. The long coils that are looping out are not the ovipositor, but are a pair of supporting sheaths that are bent aside as she drills.

Next is one of several males that were restlessly wandering up and down the tree, checking out each female. These were presumably hoping for a mating opportunity. Males of the two species look quite similar, but I think this one is M. macrurus.

Over an extended time, various females came, raised their ovipositers, and drilled in. After a time they would slowly retract the ovipositor and move on to a different spot in the tree.

At one point a female atrata actually straddled a macrurus who was already drilling, and the interloper began drilling into the same hole! You can see this in the final picture if you look closely. This “claim jumping “ is probably common among these competing species.

Experience has taught me that this orgy of horntail murder was far from over, as the wasps will continue to visit this tree over several days. I resolved to return as soon as I could, and in a later installment you will see that things were going to get pretty strange on the ‘ol “ichneumon tree”.

Stay tuned!

21 thoughts on “Readers’ wildlife photos

  1. Gobsmacked is the perfect description for how i feel about these photos! Spectacular! One can easily see why the ichneumon captured the attention of Bernd Heinrich‘a father (who buried his precious collection to protect them from the Nazis and the ravages of war, read The Snoring Bird for the story) they are beautiful…as long as one in not a horntail. These really are fantastic.

  2. People may be wondering how the giant ichneumons find their prey.
    From what I’ve read it does not seem certain how they they do it, but speculations center around smell and sound and maybe its a combination of things. They may smell the larva (they do a lot of tapping with their antennae at first). It is known that the larva are associated with a wood fungus, and there are ideas that the ichneumons sniff around for that. Sound may also be involved, as in hearing the larva in the wood.
    I also wonder if the ovipositor has sensory structures to sniff out the prey at close range. It might be somewhat simplified if they manage to drill into the larval tunnel, and then follow the tunnel with the ovipositor until they “hit larva”. This could be why the tool is so incredibly long. The ovipositor of giant ichneumons are described as the longest ovipositor in insects.

    1. I saw a talk that showed Braconidae that attack wood-boring insects tapped the wood with their antennae and use the echoes to find the host. Rather like sonar, and different densities of wood and host providing the return.

  3. Mark, your photos are terrific! I have become obsessed with dragonflies and I hope, one day, to make images as beautiful as yours.

    This past summer I stopped at a small pond to photograph a Great Blue Heron. I missed the heron, but found the pond was teeming with dragonflies. I ended up spending 2 hours wondering around the pond making images.

    I can’t wait to see your next batch of images.

    1. Very good! You are likely well equipped to photograph dragonflies with the long lens. Different species have different flying and perching habits. I do suggest you try the fields that are near water – and by that, even fields a mile or more away from it. There, dragonflies will also be abundant and your approach to them is not prevented by water.

  4. Beautiful, detailed pictures of ichneumon wasps laying eggs! Another aspect of evolution that is totally amazing. I can easily see how Creationist could latch onto this behavior as something that could not have evolved (obviously God did it). The location of prey is amazing, but how can a long, flexible ovipositor drill several inches into wood?

    1. The ovipositor is made with two blades that lock together lengthwise. They drill by sliding the blades forward and back in an alternating motion. Maybe the tips have saw teeth (?) that cut into the wood, fiber by fiber.

  5. Remarkable drama! Thanks for having the patience and skill to provide these fine pics. Sounds like the plot is thickening.

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