Category Archives: Crabronidae

Family Ties: Bees’ Murderous Sisters

A Bembix (sand wasp) female, scouting for her nest. (c) MRS 2012 All rights reserved.

It looks like a bee. It flies like a bee. Its home looks like a bee home. If threatened, it will even sting like a bee. But this doting mother, with her fuzzy body and opalescent and black striped abdomen, is a sand wasp (Bembix), and the larvae in her nest, unlike the gentle bee, feed on flesh.

Sand wasps belong to a family of wasps called Crabronidae, which is the closest relative to the bees. In addition to their similar looks and genes, bees and sand wasps share a set of interesting behaviors.

Building a Home

Despite the stereotypical image of at honey bee hive, the vast majority of bees build their nests underground. These nests generally consist of a main tunnel about the diameter of a bee body, with a variety of branching hallways terminating in elaborately constructed cells, the equivalent of a “baby room.” In each cell, she lays one egg and leaves enough food to last the larva until it leaves the nest as an adult. The larva, pictured below in its cell, resembles a maggot or a white worm. Like a caterpiller, it will pupate and undergo metamorphosis into an adult bee.

A bee larva rests on a loaf of “bee bread” (pollen and nectar), on which it will feast until it pupates. Photo taken by Dennis L. Briggs (source: Thorp, R. W. Vernal pool flowers and their specialist bee pollinators.

Sand wasps, just like their sisters the bees, build underground nests for their young. As the name might imply, they prefer to nest in sand (bees tend to prefer finer textured soils). This expecting female is beginning to build a nest for her young.

Bembix excavates her nest

Adult bees and sand wasps both feed on flower nectar, but sand wasp mothers feed their larvae fresh meat. They use their sting to paralyze flies, which quickly become baby wasp fodder. Unlike the mother bee, who gives her larva all the food it will need at once then seals the entrance to her child’s cell forever Bembix mothers continually visit their young with fresh kills. This is why most wasps lack the fuzzy, pollen carrying structures of most bees.

Choosing a Kid-Friendly Neighbohood

While some bees like the honeybee live together in one large nest, most bees prefer to nest alone. This means that a single female builds a nest by herself (where are those pesky males when you need them), and all the larvae in the nest are her own offspring.

Even bees seem to like company, however, as oftentimes these solitary females will choose to build their nests very close to each other. This could either be that suitable sites to build a nest are very scarce, or that there might be some other benefit to living so close together.

Sand wasps also like stay close. The photo above is a picture of a sand pile at a greenhouse. Each of these holes is a separate nest entrance, and in the late Spring/early Summer the sand pile was buzzing with activity.

Now, Where did I put my nest, again?

Bees and wasps both have to make several trips to and from their nest. It is therefore very important that a female be able to remember exactly where her nest is so that she can find it again later. Otherwise her poor offspring will starve and she will have wasted precious time and energy on building a useless structure. Or imagine the embarrassment of mistaking someone else’s nest for your own and entering it only to find the owner already there.

Bees and wasps typically perform a series of “orientation flights” several times a day, in which they scout out familiar landmarks, such as hills, vegetation, or a particular arrangement of stones, so that they know exactly where their nest is.

Next week I’d like to share a special set of photos I took this past summer of a series of bee nests.