2008 August 23

These are actually two different harvestmen[1]. The first one was photographed without the macro lens on a wall last year, and while it shows the spread of the legs nicely, there isn’t much detail on the body.

The second one I photographed on July 30 this year, and is probably not the same species (it has shorter legs relative to its body), but it’s close enough for our purposes.

They are not spiders, although they are arachnids. They are in the order Opiliones, while spiders are in the order Araneae. The most obvious difference between harvestmen and spiders is that spiders have two distinct body segments, while harvestmen have their bodies compacted into a single chunk that is usually kind of egg-shaped. Some of the tropical harvestmen can look pretty fancy, but the ones we have around here all look pretty similar, and are probably all in the family Phalangiidae

I’ve always thought that their eyes were pretty cool. Rather than having a bunch of eyes all over the place like spiders do, harvestmen just have two, up on a little turret on top of their heads. They even appear to have eyebrows:

From the side, the eyebrows can make the eyes look almost disturbingly human, giving them what I think is kind of a reproachful expression:

They are very well camouflaged from the top, but from underneath the ones that we have around here are a creamy white, with very substantial sockets for the legs. Given how long the legs are, it’s easy to see where they’d have to have quite a bit of musculature in the body to run them.

When you get right down to it, harvestmen are really all about the legs. I think the lead paragraph from this article sums it all up pretty well:

Imagine you are deaf and nearly blind and can hardly smell anything, but you have eight legs, each forty or fifty feet long. These legs are what enable you to assess your environment, detect rivals and predators, find mates, and procure food. That is the tactile perspective of most daddy longlegs, also known as harvestmen. As the British arachnologist Theodore H. Savory once stated, “The study of harvestmen is a study of legs.”

The legs basically act as remote sensors, allowing the harvestman to detect things by touch when they are a long way from the body. They even have flexible tips so that they can feel into little crevices and around corners.

Of course, this has a danger: what if you poke something with that leg, and it turns out to be something bigger and meaner than you, and your leg gets grabbed? Well, in that case, the harvestmen can, as a last-ditch defense, just shed the leg. It’s a sacrifice, but hey, losing one out of eight legs is better than dying, isn’t it? I’ve seen harvestmen with as few as four legs that were still managing OK. As long as the losses balance out (four legs on one side obviously isn’t workable, but two on each side is fine), they can use this escape strategy several times.

Harvestmen are predatory, but contrary to some wild stories people tell, they don’t have any venom. The ones around here can’t penetrate human skin either. I’ve held them and had them kind of scrabble at my fingerprints with their mouthparts, but that’s about it. They evidently depend on being able to pounce on their prey from above, and just mangle it to death before eating[2].

It’s kind of amusing how they find each other during mating season. A male will stake himself out on a clear surface with his legs spread, and pretty much just wait for a female to amble along and trip over him. Then he quickly grabs her, and much wrestling ensues. Then he lets her go and guards her while she lays her eggs, and afterwards goes back to his stakeout. The local species overwinter as eggs, so the ones you find in the spring are really tiny. By the end of August, we have some that have bodies almost the size of a small raisin. These are the exceptional ones, though. Most of them are smaller, about 5 mm across or so.

[1] Everybody I knew when I was a kid called them “Daddy Long-Legs”, but I never liked the name then because I thought it was insufferably cutesy. I like it even less now, after finding out that in different places the name “Daddy Long-Legs” gets applied pretty much indiscriminantly not only to these, but also to cellar spiders, and to crane flies. These are all almost completely unrelated to each other, so the name ends up being almost meaningless. It’s as if people called seagulls, dragonflies, and fruit bats “Long Flappy-Wing Dudes”, it’s unhelpful, and is practically begging for people to misunderstand which one you mean. “Harvestman” is much better, both because it isn’t so cutesy, and because it actually give some hint to their lifestyle (you are likely to see them when you are out in a field harvesting wheat, for example).

[2] Last night, S_ and I watched “The Incredible Shrinking Man”, and made fun of the scene where the shrunken hero is duking it out with a spider (the movie makers obviously didn’t really understand their spiders – they couldn’t decide whether it was an orb-web-weaver, or a roving hunter. The spider they used in the shots was obviously a tarantula, which is neither of those things – they tend to be ambush predators). Anyway, they had him in a drawn-out combat with the thing over a period of several minutes, eventually killing it by stabbing it from underneath with a pin. The thing is, true spiders are more into the lunge-grab-bite-maybe-let-go-until-it-dies-from-the-venom style of hunting, there is none of this extended looming over the terrified prey with slaver drooling off of their fangs[3]. It would have jumped him and bit him, and he wouldn’t have had a chance. He might have been able to have an extended, ultimately survivable tussle with a harvestman, though.

[3] They made the same mistake in “The Fly”. The little man-headed fly was screaming for help while the spider gradually crept up on him for several minutes. In reality[4] he would have been bitten and dead within a few seconds of the spider noticing him.

[4] Yes, yes, I know. “The Fly” is hardly “reality”, but you know what I mean.

12 Responses
  1. August 23, 2008

    I like the concept of an eye turret. Though it doesn’t seem as powerful as stereo vision. Seems they have a wide field of view – maybe good for movement detection, but not much in the way of depth perception.

    It’s kind of amusing how they find each other during mating season. The males stake themselves out on a clear surface with their legs spread, and pretty much just wait for a female to amble along and trip over him. Then he quickly grabs her, and much wrestling ensues.

    Huh… this sounds remarkably like how I met my wife.

  2. August 27, 2008

    Another outstanding post. I had no idea that daddy long legs harvestmen had eye turrets. Way cool!

    Another advantage to calling them harvestmen is that it seems so much more serious. With a name like that, you can just see groups of them gathering in a local bar after a long, hard day of pouncing on things from above.


  3. August 27, 2008

    Whoops! Looks like the strikethrough tag doesn’t work in these comments. There was supposed to be a strikethrough across my “daddy long legs” above.

    Jokes aren’t funny if you have to explain them.

  4. August 27, 2008

    KT Cat: I fixed your joke. Funny, the ‘strike’ tag works when I do it. WordPress must give the site owner some special privilege to use fancy HTML in the comments.

  5. September 3, 2008

    Excellent close ups. I used to see harvestmen in Britain but none since returning to Australia. Your post will motivate me to look harder πŸ™‚

  6. Zool permalink
    December 19, 2010

    This a really infornative piece, thanks for that !
    I was always told they were ‘ Grass Spiders’ (in Lancashire) and didnt know there was confusion between Harvestmen and Daddy-Long-Legs.
    All is clear now ! πŸ™‚

  7. Manni permalink
    April 22, 2011

    When I was little, I encountered a red and black one during a rock climbing activity with my parents. I think the harvestmen was shocked and so was I and I started crying due to my mild arachnaphobia (sp?). But after reading this, I want to encounter a harvestmen and love it to death. xD

    Instead of counting on those gnarly house centipedes with the stingers and bad attitudes, I can count on these little critters as an Earth-supporting pesticide. And, they don’t even hurt humans! c:

  8. Addison permalink
    October 21, 2012

    This is a very interesting article! I came here because a few months back I seen a whole bunch of these ” Harvestman ” on the outside of my house clumped in large groups. I never seen these things before inside or outside of my house. What is there natral habitat? Grass? trees? etc… I quickly grabbed my macro and started taking pictures and I got some pretty nasty photos of these “archinids “! Thanks so much for a great article! Keep up the good work!

  9. October 22, 2012

    Addison: I normally find them climbing walls and crossing clearings (where they are easy to spot) and in the grass and leaf litter (where they mainly live, but are hard to see). They range from little guys with bodies the size of a pinhead, up to these sprawling things with bodies the size of a raisin.

  10. Kate permalink
    August 10, 2019

    I’m so glad I found your site. I love your mix of scientific accuracy with informal, chatty details and humor. Much more fun to read than a field guide or Wikipedia. I have this image of you running around your yard with a camera looking under rocks and leaves for little eight-legged friends. I have a harvest man in my bathroom at the moment. I’m now thinking about how it came into existance because its dad splayed out his long legs waiting until his mom tripped over them.

  11. Kate permalink
    August 10, 2019

    Hum. I see my auto correct thought harvestman should be two words.

  12. August 12, 2019

    Thanks, Kate. Your image of me running around with the camera is pretty accurate.

Comments are closed.