C-shaped Soil Grub

2015 January 3

I found this white grub while digging in our garden on June 7, 2014[1]. It is one of those big grubs that stays curled into a “C” shape about the size of a quarter, and is white except for the dark head and the dark material showing through the skin of the abdomen.

There are actually a bunch of different species of scarab beetles that have grubs generally similar to this. According to this ID guide from the Michigan State University Entomology Department, it is possible to make at least a first cut at the identification by looking at the shape of the “anal slit”, along with the “raster pattern” of the hairs near the anus, so let’s look at the rear of this one:

Well, the slit is kind of a broad “Y” shape, consistent with it being a May/June Beetle grub, but the raster pattern doesn’t really look like any of the beetles they list. Well, at any rate, it doesn’t seem to be a Japanese Beetle or European Chafer, which are the two most “pesty” species that have this type of grub.

We don’t have a lot of scarab-type beetles around here that are big enough to come from grubs this size, so overall I think I have to go with the June Beetles in the genus Phyllophaga here.

So, anyway, these grubs live in the soil, and mainly eat decomposing plant matter and roots. The “pesty” species will eat so much of the roots from turf grasses that they will kill patches of lawn, making people who are fussy about their lawns very unhappy. The grubs will eat all summer, and then dig down deep enough to be below the frost line to overwinter. They may do this for a couple of years, before emerging as the large, brown beetles that fly on warm evenings in May and June, smacking into windows, bumbling around lights, and providing entertainment to small children everywhere[2]

[1] Since our last major frost of the year is usually sometime in May, our gardening season doesn’t really start until June.

[2] Last year, during one of our bouts of insect porch-lighting, we attracted almost a dozen of them, so Sam took them to school to show off to her classmates. There’s nothing quite like a big handful of large, squirmy beetles to draw the attention of third-graders.

3 Responses
  1. January 4, 2015

    Can’t … comment … much … sight of … grubs … fills me with … rage

  2. January 4, 2015

    Whew! I’ve calmed down a bit.

    The little @^%W*@@!! are real pests out here in San Diego.

  3. January 5, 2015

    I guess that’s one gardening advantage we have here in upper Michigan – there are not that many garden-pest insects that really build up to damaging levels, because the winter knocks them back so severely.

    I can’t say as much about the deer and small rodents that keep trying to kill our young fruit trees, though.

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