The Sand Wasp, an Attentive Mother – Terry Thormin

I went to Little River Pond about two weeks ago and noticed that the Sand Wasps, Bembix americana, were still flying. With the warm weather we are getting it is possible that they are still around and might continue for a while yet.

I have always liked these beautiful wasps. They are found almost anywhere there is bare soil, although they particularly like sandy areas. Unlike yellow jackets they are not aggressive and you would probably have to step on one with bare feet to get stung. They are members of the family called Digger Wasps (Crabronidae) and like most members of this family they dig nests in sand or soil. They are also solitary nesters, that is, each female digs its own nests. In ideal habitat though the nest sites can be so numerous it almost appears to be a colony. Two years ago the sand dunes at Point Holmes in Comox were thick with these wasps and I estimated several thousand in a narrow strip about 3 to 4 meters wide and about 100 meters long. Since then numbers have not been as great, but they are still fairly common.

Sand Wasp on a log

The female Sand Wasp will dig a nest hole in the ground and lay a single egg in the hole. She then catches and stings a fly which she drags, still alive but paralyzed from the sting, into the hole, and then she closes the hole with sand, pebbles or dirt. When the egg hatches the larva feeds on the paralyzed fly. At regular intervals the female will provision the nest site with another fly, each time closing the hole again, until the larva is finally large enough to pupate and turn into an adult wasp. This is referred to as progressive provisioning and is considered to be a more advanced evolutionary stage in nesting behavior. With multiple nest sites each female must be very busy attending to her young during the summer, and a large group of Sand Wasps in one area must put a considerable dent in the local fly population.

A female Sand Wasp digging a nest hole

Adult Sand Wasps, unlike the larvae, feed on the nectar of flowers and will go to a large variety of flowers. In this photo you can see the large mandibles that distinguish the females from the males. From what I have read another difference is that the females are white and the males are yellow, although the yellow will turn a pale blue with age. Bugguide however has photos of individuals labeled females that are clearly yellow. Something else to sort out.

A female Sand Wasp nectaring

A yellow male? Sand Wasp

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About annieandterry

This is a blog shared by two friends who have never met in person, Annie Pang and Terry Thormin. We both live on Vancouver Island, Annie in Victoria and Terry in Comox. All communication to date has been either by email or telephone. We are both passionate about nature and conservation and we are both nature photographers. Annie is also a very fine poet and was a concert violinist, while Terry worked as an entomologist for the Royal Alberta Museum until he retired in 2005. We hope you enjoy this joint effort to share our nature musings with anyone who is interested.

Posted on September 28, 2012, in environment, Nature and tagged , , , , , , . Bookmark the permalink. 4 Comments.

  1. Thank you for a wonderful article. I happened upon some of these I believe while counting “bees” for The Great Bee Count of The Great Sunflower Project August 17. The white and black abdomen caught my eye, and when I googled it I found your photos and blog.

  2. how do you get rid of these? I have like 8 of them in my back yard!

    • Hi Donna,
      First, unless you have some bare sand patches in your back yard, these wasps are not nesting there. They might be visiting the flowers though if there is a nesting site nearby. There is also the possibility that what you have is some other type of wasp. Sand wasps are not aggressive toward humans and are very unlikely to sting. They are also great pollinators and we sure need to be protecting and encouraging out pollinators these days. Personally I think that you should learn to live with and appreciate wasps like these.

  3. Susie Claxton

    I agree with Annie, Donna. Leave them alone and let them take care of their essential business of pollination.

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