This is what’s happening…

by Matthew Cobb

Earlier I posted this photo and asked readers to describe what’s going on.


Here’s my answer: a worker honeybee was visiting a white flower to get nectar. She was attacked by a white crab spider who was remarkably camouflaged (probably chemically, as well as visually). The crab spider had another, brown, crab spider sitting on it.

Now for the bit you may have missed – no sooner had the deed been done than a kleptoparasitic fly turned up and landed on the poor bee’s abdomen (you can just make out its red eyes), hoping to slurp up some juices from the corpse. So we have two kingdoms (plants, animals), two classes in the arthropod phylum (chelicerates and insects), two orders of insect (Hymenoptera and Diptera) and two members of the chelicerate family Thomisidae (probably both in the same genus, Thomisus). If you want to know more about crab spiders, I highly recommend Douglass H. Morse’s 2007 book “Predator Upon A Flower”.



  1. Posted January 3, 2018 at 12:20 pm | Permalink

    It’s worth noting that the smaller brown spider is a male of the same species as the large white female! Crab spider sexual dimorphism is rather extreme indeed!

    • Posted January 3, 2018 at 12:36 pm | Permalink

      Is this clear (that they are of the same species)?

      • Posted January 3, 2018 at 1:04 pm | Permalink

        I guarantee that this is a male crab spider. When they mate the male will cling to the underside of the female, wrapping his legs around her middle.
        Certain female members of the flower crab species are also able to change colour, usually white to yellow or vice versa, and there are are a few other colour variations as well.
        I am not an entomologist but have been photographing these spiders for the past three years in my garden in Johannesburg.

        In every case I have witnessed, when a crab spider takes a honey bee Jackal flies turn up almost at once.
        I read on Wiki that the bee is believed to release a type of chemical distress signal and the Jackal flies are there like a shot.
        Oddly enough, I have never seen the flies turn up when the spider has taken any other insect; fly, hoverfly, butterfly.

        • Posted January 3, 2018 at 1:59 pm | Permalink

          It certainly seems (even to me, a total non-expert) to be a male crab spider. My question was on the certainty that it was the same species.

          But I suppose a female wouldn’t allow a different species to hang on her. And, I wouldn’t expect (perhaps erroneously) that two species of crab spider would closely coexist like that (on the same plant, in very close proximity to each other).

          I suspect Catherine is a scientist with expertise in spiders.

          I was looking for the rationale behind her statement.

          • Posted January 3, 2018 at 2:01 pm | Permalink

            Indeed, I could have just clicked on the link in Cathertine’s name to see her site!

            Must get used to these modern times … 🙂

          • Posted January 3, 2018 at 2:43 pm | Permalink

            I have photo recorded several species of crab spiders, and I’ve have never seen different species intermingling.

            I have seen ( and photographed) several crab spiders (Thomasidae) share the same plant , usually a batch of Alyssum, and I have several shots featuring two white crab spiders on the same rose flower.

    • Posted January 3, 2018 at 1:44 pm | Permalink

      Ooh thanks Catherine!

    • Jenny Haniver
      Posted January 3, 2018 at 2:41 pm | Permalink

      Your blog, SpiderBytes is wonderful.

    • Posted January 4, 2018 at 3:39 am | Permalink

      I guessed male 🙂 …surely the same species otherwise why hang around?

  2. Posted January 3, 2018 at 12:35 pm | Permalink

    Ok! Perhaps the fly is a Milichiid fly, as shown doing much the same thing here:

    • Jenny Haniver
      Posted January 3, 2018 at 2:47 pm | Permalink

      I went to the Wiki. One photo shows “Milichiidae attending Rhinocoris bugs mating as the female feeds. What does “attending” mean here? I see another photo with the caption “Milichiidae, probably Desmometopa, attending a thomisid spider feeding on bee…” — I can understand the term in the second photo; but in the first photo, the Rhinocoris bugs are mating, not being attacked and fed on, so can you explain what’s going on? Why are they hanging out while the bugs are mating — are they just voyeurs or what? That last remark is a poor attempt at humor.

      • Posted January 3, 2018 at 8:17 pm | Permalink

        I think ‘attending’ is probably not the right word here, since it implies the flies are monitoring or maybe helping. They are not helping, but they are also not hurting the predators.
        The flies of course are really just opportunists. The come in to feed on hemolymph from the prey.

  3. Posted January 3, 2018 at 12:45 pm | Permalink


  4. Posted January 3, 2018 at 10:31 pm | Permalink

    What but design of darkness to appall?–
    If design govern in a thing so small.

    • Posted January 4, 2018 at 3:38 am | Permalink

      Oh! Thanks! I did not know that poem – how apt! 🙂

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