Male Horntail (Pigeon Tremex)

2014 September 20

I found this great big insect (well over an inch long) in the road on August 27, 2013. It had apparently had a bad run-in with a car that cost it one of its hindwings, and couldn’t fly.

I’ve actually been expecting to find one of these at some point, because we’ve already found some of the large ichneumon wasps that parasitize their larvae[1]. It’s a male Pigeon Tremex, Tremex columba. These are a type of “Horntail”, where the females have a prominent, stout ovipositor for laying their eggs in wood. The females of this species are also even larger, and have prominent yellow bands on their abdomens. The males obviously lack the ovipositor, but they do still have a hardened point on the tip of the abdomen.

Even though they are large, and a bit scary-looking, they are harmless. They can’t sting (not even the females), and can’t really bite, either. Which isn’t to say they are good eating – as colorful as they are, I’d be really surprised if they didn’t have some chemical defense (or at least be taking advantage of their coloration to make predators think that they are one of the similarly-colored stinging wasps).

Between being so large, and their larvae eating a fairly indigestible substance (wood), they spend a couple of years as larvae before emerging as adults. As long as a stump-stabber or other parasitic wasp doesn’t get them, they have pretty good odds of maturing, and so they are reasonably common and widespread.

While the larvae do eat wood, they wouldn’t be able to digest the cellulose unassisted. Which is why the mother wasp injects a symbiotic wood-rotting fungus along with her eggs to aid the larva in wood digestion. They much prefer dead, rotting wood, and so they aren’t any hazard to healthy trees. Which means they aren’t a forest pest, and there is no need to worry about them. They’re just one of the big, showy insects that make entomology so amusing.

[1] And now, a little more about the parasitoid that specializes in laying its eggs in the Horntail larvae. Last summer, we were down near the mouth of Cole’s Creek, and noticed that one particular dead tree had at least two of these giant ichneumon wasps busily drilling into the trunk in search of hosts for their eggs. I unfortunately didn’t have my camera along at the time. But this year, just a couple of days ago (September 15, 2014), when we went there again, I was ready with my brand-new Olympus TG-3 camera[2]. And luck was with us! Once again, there were a couple of stump-stabbers injecting eggs into the very same dead tree! As it turned out, they were too high up to photograph from the ground, so I had to lift Sandy up on my shoulders so she could get a picture. And, in spite of the generally poor light and the precarious position, she just kept shooting until she got this marvellous image:

The wasp’s ovipositor is about four inches long, and she has all but about a half-inch of it bored into the stump.

[2] The Olympus TG-3 is actually quite a camera. It is sealed against dust, shock-proof against a 7-foot drop, and waterproof to 50 feet, but that’s not the main reason I bought it. It’s also a nice size to drop into a pocket, so I can always have it with me, but there are hundreds of other cameras like that, so that’s not the thing that sold me on it either. No, what really convinced me to get it is its substantial macrophotography capability. It has a very good close-focus mode, allowing pictures of things that are practically touching the lens. It also has a removable lens ring that allows attachment of supplemental lenses. But the really big feature is that it has an automatic focus-stacking mode that appears to be unique in a mass-produced camera. If you set it for focus-stacking, what you do is focus it as best you can on your nearby subject, brace yourself, and hit the shutter button. It then goes “chuckachuckachuckachuckachuckachuckachuckachuckachuckachucka” for a couple of seconds, while it shoots a series of ten pictures at a series of focal depths (with your initial focus point being in the middle of the set). It then processes the photo set in the camera to make an extended-depth-of-field photo on the spot! Like this gelatinous blob that Sandy found on a rock (It was about a half-inch in diameter. I think it is either a clump of some kind of eggs, a bryozoan colony, or a ball of blue-green algae). I was having trouble getting it focused because of poor light, with this being the best picture I could manage taking single shots:

So I tried the focus stacking on it, and got this:

This actually looks pretty good. As a nearly-transparent blob, it actually looked pretty much like that. It might come out a bit better in the future if I brace better to keep from shifting, but for handheld, this is OK. It obviously works better for things that don’t move. For moving subjects, there is the option to just have it reel off the ten pictures so that you can sort through them at leisure, which should also be handy.

It isn’t a replacement for my 10D, which can photograph much smaller objects with better depth-of-field, but it looks to be a great supplement for photographing targets of opportunity when I just don’t have the big camera along, or for when I want to shoot a video. And if you want to dabble in macrophotography without getting a dedicated DSLR+Macro Lens combination, it looks to be a good choice.

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