Wednesday, September 19, 2012

Great Golden Digger Wasp

Isn't that an awesome name?  Great Golden Digger Wasp.  For once, the common name is much more evocative than the scientific name, which is a mundane Sphex ichneumoneus.  That sounds almost...base, icky, ignoble even.

This beauty is anything but ignoble.  Since I've learned that the larvae of this species dine exclusively on grasshopper family insects, I've become quite fond of these ferocious looking wasps and I find them extremely good looking and only a tiny bit scary.  I've been seeing individual great golden digger wasps feeding on my goldenrod blooms for the past several years, I've seen where they live. 

Yesterday, while I was weeding, I noticed one individual continually buzzing around nearby, focusing on a little patch of dirt in a small corner of the front garden.  Watching for a few minutes, I finally saw her enter a hole in the ground, then come out and fly off a minute or two later. 

She came back several times while I was weeding and watching.  I never did see her bring anything to her nest entrance, but she would enter it, come back out, and fuss around the entrance, flicking her wings and throwing a little soil around.  She acted like an anxious housekeeper, tidying up before guests arrived.

Note in several of these photos how the front legs are held together.  Apparently there are combs on the front legs that help the female move soil. 

Apparently this species builds a burrow that goes almost straight down, with "arms" radiating off to the sides.    The female will paralyze long-horned grasshoppers (katydids and similar species) and crickets, bringing each one back to the nest and placing an egg upon it, then sealing it up in one of the side chambers.  No need for refrigeration.  The hapless paralyzed Orthopteran (insect of a grasshopper-type persuasion) will remain alive in a suspended state until the wasp larva hatches and begins to eat.

There is one generation each year.  One generation annually is typical for predatory species.  Plant eaters, on the other hand, reproduce like rabbits.  Seriously... since rabbits are plant eaters.  In fact, insect plant eaters will reproduce much more rapidly than rabbits.  That's why predatory insects are so important:  to keep herbivorous insects under control.  This dynamic is one of the main reasons why spraying insecticides, which kill off both herbivorous and predatory insects, will almost always result in herbivorous insect populations rebounding crazily, meaning that you soon have a worse problem than you started out with.  You've killed off the insect predators, and they may take years to rebuild their populations to pre-spray levels.

Great golden digger wasps, like solitary bees and wasps in general, are calm and gentle.  They generally will not sting unless you try to actually handle them, but if that occurs, their sting is often extremely potent and painful.  Just leave them alone and enjoy watching them go about their business.  You'll be glad you did.


Jason said...

Great post! I'm not familiar with this wasp, but I'll keep an eye out for it now. I really appreciate posts about insects in the garden, this is an area where I want to learn more.

Gaia Gardener: said...

Thanks, Jason. I'm learning, too - thank goodness for books and the internet!

This wasp is pretty good sized - well over an inch in length - so it's hard to miss!

Casa Mariposa said...

It's always cool to discover that a fierce looking insect is really a friend rather than a foe. I've had several giant grasshoppers in my garden this year. I could have used this wasp!

Andrea said...

Thanks for this informative post, and i really am amazed at your diligent observations. Am glad for the explanation about the herbicide relationships with insect population, that is so good for your readers. But personally, I am always scared of wasps whatever they look like, I've had shares of stings from many of them, that's why! And i had an experience with smaller striped wasps when my legs accidentally brushed on its house under the bush. I ran wildly and I had my whole arm painful for a week and itchy for the next 3 weeks. Maybe there are already 5 species that stung me, hahaha!

Janet, The Queen of Seaford said...

Very interesting information!! Great find in the garden. Love new discoveries.

Gardener on Sherlock Street said...

What great photos of it working at its nest. You have such patience capturing the insects. I think I've seen a few of these around. Glad they're after the grasshoppers!

Lea said...

I wonder if we have these wasps here in Mississippi. Such a beneficial insect, and so pretty too!
Have a great day!
Lea's Menagerie

troutbirder said...

Most interest albeit a bit creepy post. The part about being kept alive but paralyzed waiting to be eaten got to me. Perhaps I've seen too many science fiction horror movies.... :)