Monthly Archives: November 2012

Repost from UC Berkeley Entomology Students Organization

This Thanksgiving, let’s be grateful to the pollinators who helped put the feast on our table. Take the squash bee, for example, who helped make sure the pumpkin in your pie was nice and tasty…

Bee Thankful, a post by UC Berkeley PhD candidate Hillary Sardinas.

a male squash bee, Peponapis pruinosa, resting in a squash flower. (c) 2011 MRS All rights reserved.

The Little Things: An Entomological Perspective

Male sweat bee (probably Halictus tripartitus) on mustard plant. (c) 2012 MRS All rights reserved.

This past Labor Day weekend, I went on a camping trip with my in-laws to Big Sur. Some people go to Big Sur with a copy of Dharma Bums in their back pockets. Other people go there to take in the beauty of the landscape and the fresh sea air. Still more people visit to retreat into the stillness of the redwood forest. Nearly all have digital cameras slung around their necks, ready to capture the beauty of the moment. But while you can find most tourists crowding around the railing to take majestic photos of things like this:

You can always pick out the -ologists because we are foolishly squatting, blocking the trail, taking photos of bugs and weeds:

(c) 2012 MRS

A cloud of these little guys, so small that they could easily be mistaken for small flies, were swarming the weeds on the side of the trail. Based on the length of the antennae, the striping of the abdomen, and the color of the legs, I am betting they are male sweat bees (Halictus tripartitus). While male bees typically come out earlier in the season than females (see The Dastardly Deeds of Male Bees), Halictus tripartitus males arrive on the scene later in the season than the hardworking females. This is because sweat bees are social, with a single female waiting out the Winter and founding a nest (complete with workers, drones, and future queens) in the Spring. Because the first generation of offspring she produces are entirely female workers (it’s a lot of hard work to establish a nest), there is no point in laying male eggs until later. Remember: male bees are pretty much useless except for mating. So in late Summer/early Fall, once the party has been long over for most bee species, we see swarms of these late arriving sweat bee males, looking for action.

Pollen grains under a SEM microscope (Dartmouth Electron Microscope Facility, Dartmouth College)

We are fortunate to live in a reality in which beauty surrounds us on all scales, from the microscopic pollen grains sticking to the hairs of the bee to the vast ocean serving as a backdrop to the scene. Our interests and backgrounds often shape the focus and scale in which we perceive this beauty. One of the great pleasures in my life has been learning how to appreciate the world in different ways, from landscapes to plants and insects to human art forms. This blog acted as a vehicle for me to share one way in which I perceive beauty in this world. It has been a lot of fun for me, and I hope that you are enjoying it as well. Thanks for reading!

Mimulus sp.. (c) 2012 MRS All rights reserved

Ryder Diaz was the student who had my desk before me. He studied stem nesting bees and was even thoughtful enough to leave a few paper tubes (used to line the holes in “bee blocks,” in which these bees nest) in one of my desk drawers.
Ryder is no longer with us, but he has left behind a superb legacy of science communication for me to follow. Take this piece about carpenter bees, the largest of the stem nesters, that Ryder created. Beautiful and informative photos, not to mention the Jad Abumrad-worthy narration.
Best of luck on your current endeavors, Ryder! If you ever decide to come back I’ll be keeping your seat warm for you…

science fan club

Take a peek into the nest of a carpenter bee!

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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.