Mud nest under flowerpot – Spider Wasps

2011 March 5

We have a small potted lemon tree that S_ put outside for the summer, so that it could actually absorb some real sunlight, have its blossoms pollinated properly, and set some fruit[1]. But, once September rolled around, the risk of frost at night got to be too much, and so on September 8 she picked it up to bring inside. The pot had been sitting on a layer of wood mulch, which left some gaps between it and the ground. Which allowed something to crawl in under it and build this mud nest:

The nest consisted of a series of individual cells made out of mud, mostly strung end-to-end. When picked up, the cells easily came unattached from each other, like so. Each cell was a bit over a centimeter long.

When we opened one of them up, we found that the inhabitant had already spun a cocoon and pupated for the winter.

Building such a nest is a very wasp- or bee-like thing to do, and so I figured that it was probably either a solitary bee or a solitary wasp. When I posted it up on BugGuide to see if anyone could narrow it down further, Ken Wolgemuth said that it was most likely a Spider Wasp in the tribe Auplopodini, and Eric Eaton agreed. Eric also said that they wouldn’t be emerging from the cocoon until spring, and since a better ID would have to see the adults, I guess we are going to have to stop here.

Spider Wasps are yet another kind of wasp that catches spiders to stock into their nests as food for the larvae. I gather that, unlike some other wasps, they prefer to catch a single large spider rather than several smaller ones. One thing that impresses me is the evident food efficiency of these things. I mean, the original spider can’t very well have been bigger than the size of the mud cell, and here the final pupa is filling at least half of the volume of this same cell. This means that the efficiency of converting spider flesh to wasp flesh is at least 50%, which is almost outrageously high.

Spiders must be very digestible and highly nutritious, is all I can say.

[1] Which worked, by the way. This lemon tree is only about 18 inches tall, and set close to a dozen fruits the size of golf balls. They finally started getting ripe around the first week in November. The downside of setting it outside was that it picked up a light infestation of some tiny, tiny web-spinning mites, but they didn’t get numerous enough to cause obvious physical damage and S_ was able to clear them out pretty effectively by swabbing with isopropyl alcohol.

4 Responses
  1. March 5, 2011

    Since spiders feed on leaf suckers, they’re bodies would be filled with already-converted sugars, right? I mean, the leaf-suckers consume raw, simple carbs and transmute them into body juices. The spiders are one layer higher on the chemical conversion ladder, so consuming them would seem to be more nutritious than eating, say, leaf hoppers.

  2. March 6, 2011

    Spiders with a dash of lemon juice would be especially tasty.

  3. March 7, 2011

    The lemon juice would also postpone the onset of scurvy.

  4. Roberto Granados permalink
    April 28, 2011

    Most spiders and insects are edible.EVEN Cockroaches(seriously).

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