Got Grubs? Help is on the Way

Dateline: August 3, 2012*

A gang of male Thynnid Wasps on dried sedge
A gang of male Thynnid Wasps on dried sedge

Ok, I know most of you aren’t lawn people…at least I hope that is the case given that a lawn is basically a biological desert from the standpoint of providing for wildlife. But we all get grubs, even those of us with meadows and I don’t know about anyone else, but the resulting May and June Bugs (Subfamily Melolonthinae) always freak me out. I still recall them buzzing and getting caught in my hair as a kid. Come to think of it, some kind of May/June Beetle (Phyllophaga sp.) did that very thing the other night when I took the dog out. And yes, I screamed like a little girl.

Male Five-banded Thynnid Wasp
Male Five-banded Thynnid Wasp

Enter my friend, the Five-banded Thynnid Wasp (Myzinum sp. possibly quinquecinctum). Back in 2009, when I was just starting out with my bug obsession, I found a gang of these guys waving in the breeze while clutching to some dried sedge. I was fascinated by their little hook, which reminded me of a “lobster claw” jewelry catch. These are the males of the species and the stinger looking thing is a pseudostinger a.k.a. a fake.

The pseudostinger reminds me of a jewelry clasp
The pseudostinger reminds me of a jewelry clasp

Males are rather long thin wasps, and my first reaction was that they have no waist (see top photo) and they seem to be the ones easily located for photoshoots. On close inspection of my photos, indeed the boy wasps do have a waist (see other photos).

Females are more robust. Shown on Goldenrod (Solidago sp.)
Females are more robust. Shown on Goldenrod (Solidago sp.)

The larvae are parasitoids of white grubs, especially May Beetles (Phyllophaga spp.) Females lay one egg per grub in soil. Larvae hatch, penetrates host, first feeding on non-essential tissues, later feeding on essential organs and killing the host. Sounds a little like they are less than humanitarians, but heck, when it comes to the June Bugs, I’m not going to invoke the buggy Geneva Convention. Pupae overwinter in the soil and the adults emerge in early summer. I guess that’s why they were abundant in recent times.

Why they hang out on dried sedge is a mystery to me, since the adults are said to feed on pollen, although my recent gang has been waving in the breeze on some primrose willow (Ludwigia sp.). I’m guessing that dried sedge has some hidden pollen/nectar within. Gotta tell the butterflies about this!

a different view of the male
a different view of the male

Since grubs can eat the roots of plants other than lawns I’m sure you are concerned about controlling these pests. Before you reach for the manufactured “Grub Control” pesticides, consider eliminating all pesticides to allow for Mother Nature to take care of your garden naturally. For this task, the Thynnid Wasp is a welcome addition to my garden.

*This is an update of a tale was originally published by Loret T. Setters on August 3, 2012 at the defunct national blog  beautifulwildlifegarden[dot]com. Click the date to view reader comments.

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