Thread-waisted Wasps

I often think my husband and I live a life different from most folk. For example, today we are each off doing our own thing - he is working on his latest spectacular piece of juniper art and I am writing this post - but we have agreed to meet at the front door at 4 pm with our camp chairs and a couple beers to head down the road to the thread-waisted wasp nesting site for an hour or so of entertainment. I realize that the idea of spending a chunk of your day sitting in the midst of a couple hundred buzzing wasps may not seem like a fun time to many but believe me, you shouldn't knock it till you've tried it!  

Thread-waisted wasp taking a break.

Common thread-waisted wasps are fascinating to watch for a variety of reasons. For one thing, they are fairly social, so if you find one at nesting time, you are likely to find dozens. Then there is the whole way they go about building their nests and laying their eggs, all of which happens over a period of a few short days in early July. 

The process starts with the wasps selecting a nesting site of bare ground with soil that is loose, but not too loose, with an abundant supply of larger pebbles that will act as stoppers and a nearby food source of caterpillars that are big enough, but not too big! Once the site is chosen, the work begins. Each female digs a hole in the ground which will serve to house her offspring and its food source. 

Although I don't know for sure, I suspect the nesting hole looks something like this:

The reason for my assumption is that part of the process involves the wasp finding the perfect rock to place in the hole, blocking the bottom portion that contains the egg and its food source without crushing them. The wasp will test the size of the rock in the hole many times, placing it and then removing it, digging some more, testing it again, then digging again until everything is perfect. Once the nest has been constructed, the wasp will place the rock in the hole above the chamber and loosely fill the whole thing back up with dirt before flying off to find just the right caterpillar with which to feed its young. According to the experts, each wasp is able to memorize the exact location of its hole by noting the details of the surrounding landscape. This is important because her search for food can take anywhere from a couple hours to several days and when she returns she will need to act quickly to finish her work and by then there may be dozens or even hundreds of other wasps building in the same small area. 

I am not sure if this is love or war but these four stayed attached for a significant amount of time!

 I have seen wasps in the past carrying caterpillars much bigger than they are but the food of choice this year seems to be a smaller model closer to the size of the wasps (maybe the caterpillars of common wood nymphs?)

Wasp with paralyzed prey

Once she returns with food, her work is not over. Just like in any population there are those who would rather steal from others than do the hard work themselves. The returning wasp is forced to drop her prey for a short time while she re-digs her previously prepared hole. She will take turns digging and then standing over the paralyzed caterpillar hoping to make it clear the prize is hers but rogues are always on the lookout, ready to pounce when the nest-builder's back is turned.

Occasionally, if the prize is big enough, a true bar brawl will break out and there will be anywhere from a dozen to two dozen wasps all rolling around in a giant mass of flailing wings and legs! Assuming the wasp is successful in reclaiming the hole and she has held onto her prize, she will then enter the hole backwards, dragging the caterpillar in behind her. 

Dragging the caterpillar into the nest.

Once she gets the food source placed in the chamber, she lays one egg on top of the helpless caterpillar and retreats back to the surface. At that point she places her carefully selected and tested rock on top of the chamber and fills the whole thing back in with dirt. Once she is done it is almost impossible to tell where the entrance to the nesting chamber is located. Despite that, occasionally another female will come along, dig up the nest, kill the offspring of the first wasp and lay her own egg on the hard-won food prize!

But assuming all goes as planned, in approximately two days the egg hatches and the larva feeds on its captive food source for the next five days or so. At that point, the larva pupates and soon after pushes its way out of the nest to begin the cycle all over again. 

The amazing thing is that all of this can take place around you as you sit and observe the action. We try to not disturb any of the nests being worked and in return, the wasps ignore us and, no doubt, call us dirty names in wasp-speak. All in all, I can't imagine a more entertaining date night!