Wasps and Spiders – a trial of toxins

Today I published a short piece in the Guardian about my sightings of wasps and spiders duelling and preying off one another. However I had more extraordinary encounters this weekend while meadow making at Blackwater. I thought it worth some extra words. But the first thing to say is that both carry toxins that would be lethal for the other: a wasp sting on a spider would surely be fatal, just as a spider bite can clearly kill a wasp.

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Even so, I was surprised to find a wasp stealing prey out of an active spider’s web (belonging to a garden cross spider). While continuing to fly (albeit in rather static hovering mode) the insect pulled the desiccated spider prey out the centre of the web, tugging the mashed protein until the spider’s silk attaching it to the web snapped. It would be interesting to know if this wasp worker had developed this kleptoparasitic practice serially, stealing from one web after another? Either way it was apparent that the spider was taking no chances and dropped clean out of its own web onto vegetation below. But the wasp’s behaviour is also high risk, as I learnt later.

The next sighting (the one I described in the paper) is here below. The wasp was already enmeshed, its aristocratic jawline and those sad black oval eyes looking extremely melancholy from behind their veil of spider silk. My article was largely about the tiny little male spider that tried to take advantage of the female’s recent catch to sneak in to mate.  IMG_5113Here he is making his move, but she was having none of it and would have eaten him i suspect if he had not been nimble.

IMG_5118 copyThe sighting that was most riveting is partly illustrated in the picture at the very top. It shows a beautiful female marble orb weaver that had just caught the wasp as I chanced upon it at Blackwater. Go back to the picture (it should enlarge if you click on it) and you can see her first moves to tackle the wasp. She approached it all from below, well away from that lethal abdominal sting. One wonders if she’d ever encountered a wasp before and how she ‘knew’ how to manipulate it. But her first goal was to immobilise the wings and head/thorax. Then, when these were tightly bound, she worked carefully around the wasp’s abdomen and firing silk from her rear spinnerets she soon had it much as you see the garden cross had got hers – entirely bound like brisket in tight silk. Even so, the wasp at this stage was very much live. I could see its abdomen still pumping vigorously.

The next part was the most remarkable. The spider moved in and i could see the exposed needle-like jaws opening wide as it injected venom into the insect. Often spiders drag large prey up to a shelter which is invariably to one side of the orb web. A leaf or a grass stem forms the A frame to a kind if silked-over tent, where the arachnid can feed unobserved. But this spider, rather than using its legs directly to move the wasp into place, pulled it up on a long strand of silk, thereby keeping the wasp at all times a safe distance from itself. Even when it had got into position in the shelter it left the wasp dangling like a load on a rope pulley a few centimetres below itself, presumably giving the injected poison time to work. Then it finally hauled the wasp in tight and started to feed.

The interesting and mystifying part for me is how the spider ‘knew’ how to work this particularly risky type of food. It may have met wasps before but spiders are quite short lived. My guess is it is not relying on previous experience to guide it. How has it acquired the ‘knowledge’ to avoid the dangerous rear end of a wasp? The aposematic warning colours – yellow and black – of the wasp are surely a helpful cue to the spider that it is dealing with something unsafe, but how did it ‘know’ that keeping the trussed-up insect on a long leash as it climbed to its shelter spot was advisable. My guess is it is all instinctual. Nothing is processed in our sense of ‘thinking’ or ‘reasoning’. The creature has inherited behaviours from generations of successful spiders, going back millions of years, and this ancient, genetically programmed suite of reactions builds into an ‘operation template’ that allows it to catch and overcome something as potentially poisonous as itself.

‘It’s a strange world Sandy!’ as Kyle MacLachan said to Laura Dern in the film Blue Velvet.

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2 Comments

  1. Interesting piece. I like the observation that the tiny male fancied his chances! Or maybe he was hungry as well as…!
    My feeling is that it is an ancient contest between these two very different groups of creatures. There are wasps which prey on spiders, wasp species which enslave spiders and wasp kleptomaniacs who sometimes pay a heavy price. The rewards of an easy meal must have led to the selection ot this strategy by some species of wasps. It may be that the penalties for the loss of individuals in such eusocial species are less than in other species? Individuals with genes for this behaviour have presumably been selected for as a result of their increased fitness. But it is the queen wasps who hold the full reetoire of the DNA which is under seletion pressure. The colonies encoding for this type of behaviour must be more successful than not, otherwise they would not exist! The loss of individual workers may not be that important if the strategy leads to the overall success of the colony.
    It’s an interesting subject – worth searching the academic literature to see if anyone has studied it.
    Came across another image of an ensnared wasp:http://www.leedingain.com/2015/09/wasp-vs-spider-6-september.html
    Best wishes,
    Ray

    Reply
  1. Spiders' shining threads turn lifeless gardens silver – The Circular Economist

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