North America’s largest scarab beetle

Dynastes tityus male - USA: Missouri, Jefferson Co., DeSoto

As one of North America’s largest, most written about, and most photographed beetles, Dynastes tityus (eastern Hercules beetle) hardly needs an introduction.  I photographed this male specimen from my collection back in December while testing my DIY diffuser for the MT-24EX twin flash and 100mm macro lens.  It’s a good test subject for such – its glossy exoskeleton may be beauty to the eye but is the bane of flash photographers, and its nearly 60mm of length demand a huge subject-to-lens distance that gives even the largest lens-mounted flash a small apparent size.  Nevertheless, the diffuser did a pretty good job of creating even illumination and preventing harsh specular highlights, giving almost the effect of an indirect strobe in a white box.

Dense setae adorn the underside of the thoracic horn of the male.

I hadn’t really noticed until I took the photos the dense adornment of setae (hairs) on the underside of the thoracic horn.  While setae in insects most often perform a tactile function, the density and placement on the horns of the males of these beetles makes me wonder if they might serve more of a display function.

Despite the overwhelming popularity of this beetle amongst hobbyist breeders and its widespread occurrence across the eastern United States (and the internet), it is not one that I have encountered with much frequency myself.  I suspect this is due to the position of Missouri near its western limit of distribution – likely a function of the species’ preference for moist treehole cavities with rotting wood in which the larvae can develop.  This particular specimen was given to me many years ago by a nursery grower in Jefferson Co. during my first job out of graduate school – before I’d ever found one myself, but since then I’ve encountered perhaps half a dozen or so at blacklights in mesic forests across the eastern Ozark Highlands.  Most recently (last summer) I found a female sitting on my driveway, apparently attracted to the mercury vapor lamp above the garage that I leave on occasionally during the months of June and July just for such purpose.

Copyright © Ted C. MacRae 2011

28 thoughts on “North America’s largest scarab beetle

  1. Quite a few dynastids have those brushes of setae on the underside of the horns: D. hercules, varous Golofa spp., and there are also other beetles with large sexually selected structures that are covredin setae: Rhinostomus barbirostris springs to mind. As far as I know there has been no research whatsoever into their function. I have noted that the case of the dynastids the setae are on part of the horn that is likely to come into contact with the dorsal side of an opponent during contests, so perhaps they serve to improve grip?

    Like your blog

    Rob Knell

  2. A great looking beetle, your diffusion system is working well. How I wish we had such handsome beasties up here in Alberta! I haven’t seen anything (alive) like this since my time in South Africa. Are the scratches on the top of the head battle scars?

    Looking at the elytra, the red spotting on the pale background looks like an interesting subject for some abstract macro photos…

    • The scratches could be battle scars, but more likely it was rough handling post-mortem – the guy who gave it to me wasn’t an entomologist but thought it was impressive and had it sitting on his desk.

      Elytral abstracts – sounds like an interesting idea!

      • I just ran across a live one tonight while taking out the recylcing, and I came across your post while doing a little searching for more information. The live one that I found has some similar scratches on it (I, of course, ran back in the house and grabbed my camera and macro lens, and shot a few photos), so I suspect the battle scar hypothesis could be reasonable.

  3. Jarman and Hinton (1974) studied the grasping ability and forces exerted by the horns of male D. hercules. They noted that the dense setae on the ventral surface of the pronotal horn increases friction and so aids grip. This is especially important when grasping other males that have rounded and smooth surfaces, such as the dorsal surface of the pronotum and elytra. – from Ratcliffe (2003)
    The setae on D. tityus surely serves the same purpose.

    • Cool – actual research supporting the grip hypothesis. As I mentioned above in response to Rob, that does sound more plausible than display, considering that these beetles probably don’t have exceptional vision.

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  6. We iive in South Texas and found one of these incredible guys on our porch. He’s still alive and my nine year old daughter was wanting to observe him for a while before releasing him, he’s in a large habitat/aquarium, We’re trying not to stress him, but we were wondering what he would eat. Any sugestions?

    • They make fun, impressive pets. Sliced bananas, apples and grapes oughta keep him happy for several weeks. Put mulch in the bottom of the terrarium and a good-sized chunk of wood for him to perch on.

  7. My wife just found a male in the yard while working her flower garden,I’ve never seen anything like this before.We live in the upstate S.C. just outside the town of Belton have it a jar but will release it later have to show afew old timers today is:04-09-13

  8. If you are still watching this post, do you know if there are records of Dynastis tityus in western Missouri (KC area)? Lots of great Lepidoptera record data popularly available but haven’t seen the equivalent for beetles. Thanks!

    • Hi Matt – my specialty is as far as Missouri records is limited to buprestids/cerambycids/cicindelids. I have no doubt that the species occurs in the KC area – to find it I would imagine original forest remnants would be the best place to look. Even here in eastern Missouri, however, finding them is pretty hit or miss – I’ve seen less than a dozen in my 30+ years of collecting beetles.

      • Thanks, Ted. One more question if you don’t mind. Were yours found with lights or by day in the field (or some of each)? Indeed doesn’t seem to be any proven method of locating them from poking around the web, most appear happenstance even by those with experience.

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  10. Just found one on the screen of my back porch! Not a fan of bugs so def.gave me a scare. I put him in a jar and he is on his way to an entomologist tomorrow at the Tidewater Research Center in Suffolk Va.


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