Monday, August 31, 2009

Grape is Blooming

Wild grape is blooming along the edge of the Campus Pond here at the University of Massachusetts in Amherst. That is cause for excitement for me because the blossoms are a magnet for a variety of wasps and bees. While occupied with nectar-sipping, they are fairly easily approached, though they are still constantly on the move and wary of my camera.

I have seen at least three species of yellowjackets alone, including the “aerial yellowjacket,” Dolichovespula arenaria, also known as the “Sandhills hornet.” They build their paper nests aboveground, often under the eaves of houses.

Another species of yellowjacket commonly seen right now is Vespula vidua. They nest underground, in abandoned rodent burrows and other natural cavities. Like the aerial yellowjacket, they are strictly predatory on other insects, especially flies, which they chew up and feed to the larvae back in the nest. They do not scavenge at picnics and barbecues like more abundant urban yellowjackets.

Paper wasps are also social insects like the yellowjackets, but their colonies are much smaller in number of individual wasps, and the nests are uncovered paper combs. Here, the most abundant species is the introduced “European paper wasp,” Polistes dominula. They have been immensely successful at exploiting their new homeland, maybe due to their aggressiveness. This worker repelled all other wasps from its perch on these blossoms. Why it was guarding that particular bundle of flowers is beyond my understanding of the species.

Solitary wasps also flock to grape flowers. This grass-carrier wasp, Isodontia mexicana, is a case in point. They are fairly easy wasps to recognize because they usually alight with their wings splayed out away from their bodies, exposing the thin “wasp waist,” a petiole that links the abdomen to the thorax.

Much larger than the grass-carrier, but in the same family (Sphecidae) is the “great black wasp,” Sphex pensylvanicus. They tend to flatten their wings over their backs while probing the blossoms with their tongue-like mouthparts. The brilliant blue reflections of the membranes make them a truly spectacular insect to observe.

Perhaps the most regal of all the wasps at the grapevines is the aptly-named “great golden digger,” Sphex ichneumoneus. Females of this species, like those of the great black wasp, dig burrows in the soil, storing paralyzed katydids inside as food for the single larval offspring that develops in the subterranean nest.

I enthusiastically recommend wasp-watching to anyone with even a passing interest in insects. They are placid animals when foraging for the carbohydrate-rich nectar that fuels their flight. You can literally get nose-to-nose with them without arousing their aggressive streak. See how many species you can observe, and share what you find with others.

3 comments:

  1. Hey, BugEric! I have a butterfly conundrum and you were recommended for a possible answer. I've been trying to figure out what parasitized a monarch chrysalis in our garden at work. You can see the image (and my conclusions to date) at my blog: www.adknaturalist.blogspot.com

    Any help would be welcome!

    ReplyDelete
  2. Hi Eric,

    We are all in wasp-mode at this time of year! Great article - it makes me want to plant grape vines just to attract more wasps.

    My entomologist friend at The Home Bug Garden now has two great posts on wasps. http://homebuggarden.blogspot.com/

    ReplyDelete
  3. Thanks, guys. I'm busy, busy, with next to no internet access (except at work), so it may take me awhile to respond to your comments in-depth. Thanks for understanding.

    ReplyDelete