Seemingly correct answers came quickly to yesterday’s inaugural Super Crop Challenge, which featured a curious structure atop a harvestman (class Arachnida, order Opiliones) that I encountered while hiking the lower North Fork Section of the Ozark Trail in extreme southern Missouri. “Seemingly” I say, because even though some points were earned, others remained left on the table – the organism was rightly recognized as a harvestman, and the structure in the photo does indeed contain the ocelli (or eyes). However, nobody actually named the structure itself (see update below) – the ocularium (ocular or optical tubercle would also have been accepted). Hey, I’m pedantic and proud!
As near as I can tell, this individual belongs to the genus Leiobunum (family Sclerosomatidae). Species in this genus are notoriously difficult to identify; however, the super long legs, dark dorsal stripe, pointed abdomen, and very long palps with “knees” that extend dorsally to a level well above the ocularium suggest a male L. vittatum or one of its close relatives (Schulz 2010). Leiobunum vittatum is a common inhabitant of wooded habitats across the eastern U.S.
I took this shot with an MP-E 65mm macro lens at about 2.5X. The short working distance of the lens at this level of magnification makes it difficult to photograph these longer-legged species in lateral profile due to their habit of “waving” their especially elongate 2nd pair of legs in the air as pseudo-antennae – one touch of any part of the camera sends them scampering. I chased this guy back and forth across a downed tree trunk for some time before I finally got lucky when it encountered some prey (note the long structure extending down from the mouth area – I believe it is the antenna of a tiny, nymphal blattodean) and became distracted just long enough for me to close in and fire off a couple of close shots. He was actually closer to the underside of the log, so when I took this photo I was leaning far over the log with the camera almost upside-down!
Okay – Art earns points for being the first to identify it as a harvestman, while Geek snaps rare duplicate ID points for using the order’s scientific name (no complaining – scientific names will always get points on this blog). Art, Aniruddha, and Geek also get half-points for mentioning (in order of correctness) eye, ocelli (technically more correct, but wrong plurality), and ocellus (yes, only one is visible – did I mention my pedantic tendencies?). However, I’m going to declare arachnologist and Opiliones specialist Chris as the winner of this round for his impressive display of generic-level identification based on the meagerest of evidence!
Update 11/22, 11:00 a.m. – actually, Chris did name this structure in an email sent to my office address while the comments box was unchecked and, thus, earns a clean sweep of this challenge.
Photo Details: Canon 50D w/ MP-E 65mm 1-5X macro lens (ISO 100, 1/250 sec, f/13), Canon MT-24EX flash w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask).
REFERENCE:
Schulz, J. W. 2010. The Harvestmen of Maryland (accessed 20 November 2010).
Copyright © Ted C. MacRae 2010
Beetles In The Bush 
Their legs do get in the way, don’t they? I have tried approaching them from the top for a dorsal view, but your excellent profile accentuates the eyes so much better.
The shorter-legged species aren’t so difficult. However, not all opilionids have such a distinct ocularium – this lateral profile shot was really the only shot that I wanted.
I really wanted the cropped structure to be from a larval cicindelid, but couldn’t force it into that ID.
Looking forward to more of these…
A tiger beetle might have been a little too obvious, at least for the first one. I’ve now established that anything goes! 🙂
You call those long palps? As Chris would be able to tell you, we do long palps properly down in New Zealand:
Megalopsalis fabulosa
(I think it’s actually the chelicerae that are super-massive in those guys)
My god, those are impressive choppers!
How I would love to visit your curious little corner of the world some day.
That’s not Megalopsalis fabulosa; it’s a Pantopsalis, possibly P. albipalpis. Pantopsalis species are impressive enough, but they’re absolute tiddlers compared to M. fabulosa.
How does something like that even evolve?
Is this another one?
Nipponopsalis (don’t know the species). Not a New Zealand genus, its found in north-east Asia. Also a completely different infraorder from the New Zealand species, it belongs to the Dyspnoi rather than the Eupnoi. The large chelicerae have evolved independently in that genus from the New Zealand taxa. Megalopsalis and Pantopsalis have large chelicerae in the males only; they’re probably used in fights between males, but this has never actually been observed as far as I know. In Nipponopsalis (and the superficially similar European genus Ischyropsalis), the large chelicerae are present in both sexes, and are used to crack open the snails that these harvestmen specialise in feeding on.
Fascinating. I have a newfound respect for opiliones, which I fear I’ve given short schrift before now.
If you haven’t seen it, Troy Bartlett just posted a fabulous photo of a gonyleptid harvestman that he saw in Brazil.
Damn, not only was I wrong on the ID but I was selling the NZ harvestmen short!
😀
Opilionids are currently on my List of of Arachnids That Are Not Gross And Creepy, but daaaay-um. That guy might get kicked off the list. However: it is, regardless of List status, hella-cool.
Yeah, those are some crazy chelicerae!
(The pedipalps, by comparison, are rather mundane.)
Okay, we’ve seen some crazy palps and some crazy chelicerae – are there any opiliones that have crazy both?!
Not that I can think of off the top of my head. For the most part, Laniatores (short-legged harvestmen) go for enlarged pedipalps while Palpatores (long-legged harvestmen) go for enlarged chelicerae. I couldn’t tell you why. Cyphophthalmi (mite-like harvestmen) generally eschew such extravagant frippery altogether.
My new favorite phrase!
Hi, Stumbled on your site and saw your great harvestman picture. The animal is a male Leiobunum crassipalpe, a close relative of L. vittatum that ranges from southern Missour, northern Arkansas and eastern Oklahoma.
Hi Jeff—great, thanks. Nice to have a species ID on the critter. What do you see that distinguishes this species from L. vittatum?