An explosion of Opiliones

December 31, 2013 • 2:06 am

by Matthew Cobb

If you’re phobic about Arachnids, move along quickly!

These things popped into my Twi**er feed. The first I can’t embed as it’s one of those gif-esque 6 second Vine thingies that Twi**er have invented and WordPress doesn’t like the embed script.

Here’s the link and here’s a verbal description: chap/chapess (user ‘Paglo?’) pokes a furry looking bit of grot in what looks like the edge of a swimming pool. And then something happens, involving Opiliones (or harvestmen, or daddylonglegs – for more common names, see at the end)…

Here’s another example of the same phenomenon, from Arizona:

and another

and another, less dramatic:

My copy of the superb Harvestmen: The Biology of Opiliones by Ricardo Pinto-da-rocha, Glauco Machado and Gonzalo Giribet is at work, so I can’t investigate why these species of Opiliones apparently have an affinity for grouping together in furry objects (though if it’s for camouflage it would seem pretty damn effective!). Can any arachnologists (opilionogists?) chip in?

I can’t emphasise enough how good that book is, by the way: you can read my rave review from the Times Literary Supplement here. Earlier in the year, arachnologist Chris Buddle tw**ted the best bits as he read it, under the hashtag #OpilionesProject. You can read 10 fun facts Chris learned along the way here.

Here are some of my own fave things about harvestmen, taken from some of the slides for my second year lectures on invertebrates.

• 6000 species known (really 10,000?)

• Found up to 4000m

• Virtually nothing known about African, tropical Asian or Amazonian species

• Earliest known specimen from the Rhynie chert in Scotland, about 400 MY old (fantastic pics here).

• Omnivorous, but many carnivorous (though not venomous).

• Can eat fungus or bananas or cappuccino mousse…

• Masticate food (unlike spiders)

• Generally XY sex determination

• Internal fertilization – male penis is everted version of ovipositor

• Not all of them look like classic form. Can be short and stubby or have very nasty grabby chelicerae (front appendages shared by spiders, scorpions, sea spiders etc)

• Generally only 1 pair of eyes

• Do not produce silk

• No pedicel connecting tagmata, externally segmented abdomen

• Latin name comes from Opilio (”shepherd”), allegedly because shepherds in some parts of the world walked around on stilts (honest!).

• Various common names, many of which have to do with harvesting:

Kosec (“reaper”) –  Slovakian,

Hooiwagen (“haywagon”) – Dutch,

Pedro – Spanish (St Peter’s Day)

Zatomushi (“blind bug”) – Japanese

Lukki – Finnish (means nothing!)

h/t Morgan Jackson (@BioInFocus) and Bug G. Membracid (@bug_girl)

36 thoughts on “An explosion of Opiliones

  1. Those bundles of fun look so cool. It seems a shame to disturb them like that. The urge to poke must be irresistible, unless they could fly or jump or talk in a way we could understand. This website has made me into a lover of spiders and other sweet crawly things. If you are an arachnophobe this video should change your mind

    Your link to the TLS review goes to a 404 error. I looked for the book on Amazon, it is almost £100. Is there anything more simple like Fortey’s Trilobite or Von Frisch’s Dancing Bees that I could read?

    1. Have fixed the TLS review link (it links to a PDF so look in your downloads folder). Yes the book is horribly expensive – but you can ask your local library to buy/borrow it. There’s no beginners’ guide as far as I know – not sure it would be a big seller (folk don’t like Arachnids!). – MC

    2. It is not about all arachnids, only spiders but I recommend “The Biology of Spiders” by Foelix Rainer. It is pretty dense but I enjoyed it immensely. Spider biology is fascinating.

  2. I have always know Crane flies as “daddy long legs”, not spiders.
    We had a mass invasion of the crane fly larvae, or “leather jackets” at home when I was a kid. They came pouring out of a hole in the concrete on our back path for nearly three days. The only way to get rid of them was to throw continual buckets of boiling water down the path, otherwise we would have had a biblical-style plague of the things.
    Spiders are far cooler.

    1. I was confused for years about Daddy-long-legs, because in Australia they are definitely spiders. They build large messy webs and hang around in quiet places. The bathroom is a favourite. We have harvestmen too but they aren’t obvious.

  3. When I did bat research in caves of W. Va., we labeled DLL groupings found near entry crawl ways as a “pubic cluster”

        1. What a wonderful link you gave! It shows jaw-dropping diversity in this group! Amazing. Any harvestman lovers (or haters) will be transformed by those 145 images.

  4. Many years ago, when the spouse & I lived in a ground-level apartment, we noted a large harvestman traipsing across the back porch cement. We were having spaghetti that evening, and the spouse put out a pencil-eraser-sized bit of spaghetti sauce meat. I told her, “Sure, the daddy long-legs is _really_ going to go for that.”

    Blew my mind when the critter actually picked it up and walked away with it!

    1. A couple of clarifications:

      1) The harvestman picked up the morsel with his mouth parts. It did NOT use a pair of legs for this. It walked away with its prize using all 8 legs.

      2) The bit of spaghetti meat was _cooked_, not raw.

    1. How about to look like an enormous furry caterpillar? Or just a kind of lichen or plant? Anything but what they are, highly edible little morsels.

  5. Great post! Aggregations are most likely “defensive” but other hypothesis have been suggested, including the micro habitat created by aggregations provides more optimal conditions for individuals. It’s also been proposed that defensive alarm chemicals (& other signals) spread more quickly/easily with a group.

    Aggregations tend to include males and females and subadults, and can even include multiple species, which is totally fascinating. Aggregations are typically “layered” and can be truly huge- I think the largest on record is over 70,000 individuals (on cactus, if memory serves).

    Oh, and the best common name for them? Grandfather graybeard (I have no idea why that’s a common name for Opiliones!)

  6. Wow – I am intrigued and repulsed by large groups of anything alive & this is truly strange.

    I normally don’t mind harvestmen (though I still wouldn’t want one to walk on me) but I think many arachnophobes are not as afraid of harvestmen. See, we know deep down that they aren’t really spiders.

    1. No harvestmen (harvestman?) that I know of can do anything but tickle you. Certainly not in our area of the planet. They are the ‘gateway’ critter for getting children to handle spidery things.

        1. That is natural. What I do is concentrate on some of their details, rather than try to take in the whole spidery thing. Focus on an elegant color pattern, or intricate joint in the legs. With tarantulas I find myself staring at their cute little fuzzy feet.

  7. I have fond memories of harvestmen. On archaeological digs in Mexico it was very common to find our excavation areas (which we covered with sheets of plastic at night) occupied by clumps of hundreds of them in the morning. Our workmen always told us that having “mingiches” (harvestmen) in one’s house is a sure sign of good luck, and I fuess that was the case even if the house was being excavated and 1500 years old.

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