Spider Sunday: Running crab spider

Today’s spider was (is) a real challenge for me to determine which species it belongs to. After considering the options, I think it’s a member of the Philodromidae family or the running crab spiders. Quite possibly the Turf running-spider (Philodromus cespitum).


The reason for my uncertainty is that running crab spiders resemble crab spiders (Thomisidae family). In the past, both family groups were considered one big family by taxonomists. In addition, some species look so much a like, that only by dissecting them, the actual species can be determined. So what are the differences (if any) between running crab spiders and crab spiders?

According to a source, the 3rd and 4th pairs of legs of running crab spiders are longer than those legs in crab spiders. Also, the 2nd leg pair is the largest. The hunting behaviour is different too. Crab spiders tend to wait until a prey is within reach, but running crab spiders actively hunt by running towards their prey and ambush them in that sense. While observing this spider, I found it to be an active fellow. And by comparing different pictures, looking closely at the length of the 3rd and 4th leg pairs, I’m pretty confident that this is a running crab spider (even though my spider was missing a leg 😦 ).

If it is indeed a running crab spider then based on the markings, it is likely a female turf running-spider. This is a common species. However, to be sure, the spider had to be dissected to look at the genitalia. I’m not the type to do this. I enjoy seeing and photographing animals, but I try not to disturb them (too much)! I’m only giving them an opportunity to shine on my blog 🙂 .

Unfortunately, the search for a name was more exciting than the information I found on this species. The turf running-spider is not so popular, so there isn’t much information available. The fact that for an accurate determination, the spider has to be killed, is not helping either.

While sorting my pictures to see if I previously encountered this spider, I found a picture that a former coworker of mine had sent me of a (running) crab spider keeping a close eye on a prey. See if you can spot the spider!


Here are some sources I used to learn more about (running) crab spiders:





5 thoughts on “Spider Sunday: Running crab spider

  1. Amazing capture! Generally people have an aversion to these critters…you are doing a great job! 🙂
    I have a friend , who has documented a lot of spiders 🙂

    1. Thanks Indira! I hope my blog helps in familiarising people with these (and other) creatures. For me it’s also a great tool to learn more about the natural world and connect with people from all over the globe 🙂

  2. Nice blog! A running crab spider visited me a moment ago and I took and put him outside. Found out that he was from the genus Thanatus.

    I think it’s pretty easy to tell running crab spiders from crab spiders. The running type usually hold their two front pairs of legs more straight and use them for walking, and their faces are more rounded. Crab spiders have flatter faces and they don’t use their front pairs of legs that much when walking. =)

    I would never dissect a spider either. Most of them are nice and intelligent critters, and deserve to live a good life. They just want to get by. =d ❤

Please share your thoughts!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s