All you ever wanted to know about Harvestman, but were too afraid to ask

Harvestman, Daddy Longlegs, Shepherd Spider, Grandfather Greybeard: all colloquial names for members of the Opiliones order. Yes, they have eight legs, but they’re not actually spiders. In fact, according to Chris Buddle, professor of arthropod ecology at McGill University in Montreal, Canada,

“Comparing a spider to a harvestmen is like comparing a blue whale to a chimpanzee.”

Harvestmen_Close_Macro

 

But how do you tell the difference between a harvestman and a spider? Well, harvestmen don’t have a waist or separate abdomen. Cellar spiders are often mistaken for harvestmen because of their long spindly legs, but they have a definite waist and also make silk. And don’t get confused about Daddy Longlegs either. Chris was surprised to learn that in the UK what we call the Daddy Longlegs is actually a crane fly.

If you want to know more about these unfamiliar creatures, you can buy the book by Ricardo Pinto-da-Rocha, Glauco Machado and Gonzalo Giribet called Harvestmen: The Biology of Opiliones

Spiders01

This will set you back about £100, though, so you’d have to be pretty interested to shell out that kind of money.

Chris Buddle bought the book. He has studied other eight-legged creatures, such as pseudoscorpions and wolf spiders, but he didn’t know very much about harvestmen at all. Having paid out all that money, he then wanted to make sure he read the book, so he started the Twitter hashtag #OpilionesProject, with the authors’ permission. As he told me when I contacted him at his office,

“I didn’t care if other people were interested. I did it, initially, for entirely self-serving reasons. The motivation was to give me time and motivation to read the book and get used to Twitter.”

His first tweet was on April 3rd 2012 and it took him until February 26th 2013 to finish the book. They are not the typical “charismatic” animal that so captivates public imagination, so he was surprised, but delighted, to find a pretty passionate bunch of people who were interested in the details and beauty of these understudied creatures.

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So, what did we learn about Opiliones? They don’t make silk, they’re not venomous and some of them glow under UV light like scorpions do. Unlike all other arachnids, the males “present intromittent genitalia derived from the male reproductive tract” i.e. they have penises. They aren’t hunters like spiders, for the most part, but tend to scavenge. From time to time they form aggregations, where they group together for several weeks, or even months. The largest aggregation on record was 70,000 individuals! Nobody knows quite why they do this, though defence against predators and regulating body temperature have been suggested.

And there are lots of other things we don’t know about them. I asked Chris what the most important areas of research are. He said we still don’t know the fundamental life history of an individual, understanding of their physiology and development needs work, and it would be good to get some studies of their diversity. This is all pretty basic stuff, why don’t we know this? Chris has an idea:

“There are some really serious phobias out there. I’m very aware of that. Phobias prevent study of arachnids.”

Not for everyone, though. In fact, Chris got a lot of queries for tips on how to capture and keep harvestmen by interested amateurs, so we may get results from some citizen science. Meanwhile the main aggregation of opilionologists seems to be in Brazil, so expect more stories about Brazilian arachnids.

Though the Opiliones Project is over, Chris has compiled the tweets into a pdf that you can download from his blog, Arthropod Ecology. But he did admit to having glossed over those chapters that didn’t translate into 140 characters, like taxonomy and physiology, so if you’re interested in swelling the ranks of scientists studying the Opiliones order, you better buy the book for yourself.

Kim Biddulph

Kim is a humanities graduate who realised, after working in museums for ten years, that she should have studied science. She has converted to biology, mainly through the medium of spiders. Like most people, Kim was scared of spiders, but after having a child has decided not to be and to learn all about them instead. Kim has also had the great honour of working on the education programme for local schools at Darwin's family home, Down House in Kent.

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10 Comments

  1. Joe Strobhert

    I have been fascinated by these animals since I was a child. They do not seem to fear humans or cats but also are not aggressive. There is one I have been sharing our kitchen for several weeks now. He/she has one wall where it is happy to roost for a day or more. I have had to gently brush it off my arm and face several times, and have felt bad about my own ingrained prejudice.

  2. kat

    We have always called these “pea on legs”! oh look there goes a pea on legs! we kinda figured they weren’t spiders as there just all wrong but what on earth they are and what the point of them is I don’t know! other than being amusing creatures that go well with the “war of the worlds” tune….. sometimes… I just shout ullarrrr when I see one! it makes me feel better! 😀

  3. Felipe

    Having read this I thought it was very enlightening. I appreciate you spending some time and effort to put this article together.
    I once again find myself spending a lot of time both reading and posting
    comments. But so what, it was still worthwhile!

  4. Jackdaw

    A harvestman invaded our kitchen and survived attacks from our boxer and our chihuahua.

    A tough nut on stilts.

  5. Jilliej

    I found this very interesting and was able to identify these creature which I found around my house but have been killing because I didn’t understand them…from now on they are free to roam 😊 Also did not know that this species of arachnids even existed so thankyou for more knowledge gained.

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