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An Irisdescent Green Sweat Bee (photo by Cyrus Khamak)

Sweat bees are tiny bees of the family Halictidae.  They take their common name from their affinity for human sweat, which they lap off of our naked skin for the salts and electrolytes therein. Sweat bees are small (at least to us) and tend to measure between 3 and 10 millimeters in length. A few species have thick robust bodies, but most are slender and delicate.  They tend to be glossy black, but some have exoskeletons which are gorgeous shades of metallic gold, green, purple, or blue.

The majority of sweat bee species nest in the ground (although a few build their homes in dead trees).  The social behavior of sweat bees runs the entire gamut of bee conduct: the University of Florida Department of Entomology Website states, “species can be solitary, communal, semi-social, or eusocial.”  Sweat bees therefore greatly interest entomologists who are studying the development of eusocial insects—those hive-minded insects which form colonies made up of a mass-reproducing queen served by a number of biologically sterile individuals.  Most species of sweat bees live together in a simple underground tunnel-hive where they act more like roommates than like city-states, however some halictids do indeed create caste-based societies (albeit not as large and elaborately organized as those of honey bees or ants).

Sweat bees mass-provision their larval offspring—which is to say they stick a mass of pollen inside a waterproof cell, place an egg on it, and seal then it off until a functional adult emerges (as opposed to honey bees which lovingly feed the larva as they develop).

Halictidae species are immensely important to flowering plants.  They are critical pollinators for many wildflowers, crops, and fruits.  Therefore, although the creatures usually fly beneath our notice, they have a tremendous importance to humankind and to ecosystems as a whole. Not all sweat bees are virtuous workers: some species are cleptoparasitic and lay their eggs on the pollen masses accumulated by another species of bee.  A handful of these little bees are outright parasites in the manner of the parasitoid wasps.

A Sweat Bee Gathering Pollen and Nectar from a Poppy

Like their fiercer large relatives, sweat bees are capable of stinging, however their stings are weak (which is fortunate considering their affinity for landing on us).   Sweat bee stings rate a lowly 1.0 on the Schmidt Sting Pain Index (a remarkably poetic scale for rating the discomfort caused by hymenopteran venom). I have been stung by a sweat bee and the sensation was that of a needle-like itch which penetrated deep below the skin and then subsided almost immediately.

The sweat bees are cosmopolitan, which means they can be found throughout all similar habitats in the world (although they are thin on the ground in Australia and South East Asia).  However the sweat bees are cosmopolitan in another way: alert reader, Michael Donohue (who is always on the look-out to identify his fellow native New Yorkers), sent me an article which details the discovery and naming of a new species of Halictidae, Lasioglossum gotham, which Dr. John Ascher, a bee researcher at the American Museum of Natural History, discovered in Brooklyn Botanic garden in 2009.  In the NY Times article about the discovery, Ascher describes how New York City has a very rich diversity of wild bees.

Lasioglossum gotham–actually about the size of a rice grain (photo by American Museum of Natural History)

One of the delightful things about the hymenoptera—the wasps, bees, ants, and termites—is that many different species remain unknown to science.  There are times when it seems frustrating to live in a world where most life forms have been categorized and collected, however the fact that some of the hymenoptera make their homes in the most isolated tropical wilderness means that vividly distinctive (and hitherto unknown) bees, wasps, and ants are found from time to time. Last week an entomologist exploring the remote rainforests of Sulawesi discovered a new species of immense predatory wasps with jaws longer than its front legs. The predatory wasp is shiny black with evil gothic barbs running along its abdomen.  Although the wasp’s habits and behavior are still unknown, its size and its formidable jaws would seem to indicate that it is a predator.

Lynn Kimsey, director of the Bohart Museum of Entomology and professor of entomology at the University of California, Davis, discovered the wasp as part of a biodiversity expedition to the remote forests of Sulawesi.  She plans to name the wasp after the Garuda, an eagle-like divine being from Hindu legend which is associated with speed and martial prowess (and with the constellation Aquila). The Garuda is admired and known in many different myths from Southeast Asia but it is particularly associated with Indonesia—and has become something of a national symbol

The Garuda

Sulawesi, the fourth largest island of Indonesia has long been an ecological treasure trove thanks to multiple isolated peninsulas (complicated geology has given the island has an unlikely shape), impassible mountains, and huge wet forests located only a few degrees from the equator.

Sulawesi

An Iridescent Wasp on a Linen Tablecloth

Today I would like to start a brand new animal category concerning the most gifted of the social insects, the superorder Hymenoptera, which consists of wasps, bees, ants and sawflies (along with some other oddballs which are less frequently mentioned).  Hymenoptera are arguably among the most successful creatures on the planet.  Their behavior can be almost embarrassingly humanlike and they are famous for building elaborate constructions, going to war, taking slaves, farming fungi, and crafting rigid city-like social hierarchies. However, of all life forms on earth, the hymenoptera are some of the most vividly alien: cuttlefish do seem downright cuddly when compared to the horrifying digger wasps.   A sociologist could happily draw parallels between a bee hive and a city until he looked at the details of bee reproduction, at which point he would probably break down and weep.

The Hymenoptera are not as ancient as either the mollusks or the mammals (if it is fair to compare an order with a phylum or a class).  They originated in the Triassic and did not develop the successful social organization which is now such a defining feature until the late Cretaceous.   The first hymenopterans were the xylidae, a family of sawflies with a minimal presence on earth today but with a long pedigree. These first sawflies fed on the pollen and buds of the conifer stands beneath which the first dinosaurs developed (and under the roots of which the first mammals cowered).  The rise of the flowering plants in the Cretaceous led to a leap-forward for these pollen-eaters: complex flowers then evolved in tandem with the hymenopterans. It was also during the Cretaceous that the ants and termites split from the vespoid wasps.  The earliest honey bees of the familiar genus Apis evolved at the end of the Eocene bt they were preceded by all sorts of hymenopteran pollinators.

A Sawfly Fossil (Hymenoptera: Symphyta)

I mentioned above that, for all of their familiarity to us, the Hymenoptera are disturbingly alien.  In fact as I have been writing this comparatively tame post, a dreadful sense of formication has stolen over me and I find myself brushing phantom ants from my limbs and feeling the terrible pang of yellowjacket stings from childhood.  The hymenoptera are frequently the basis of the extraterrestrial enemies in science fiction.  Although people are occasionally stung to death by wasps or ripped apart from within by driver ants, it is something larger and less tangible which makes the hymenoptera such reliable villains. I have watched the soldier bees snip the wings off of wasps trying to invade my grandfather’s bee hive and then toss the invaders’ writhing bodies from the painted ledge—all while a river of worker bees went out and came back laden with pollen.  There is an alarming touch of civilization to these social insects: a hint that they are utilizing the same kinds of organization and communication which have made humans such a success.  And, in fact, the social insects are a huge success—ants alone are estimated to constitute a substantial portion of the animal biomass of earth (to say nothing of termites, bees, wasps and the rest).

Yellow Jackets on a Coke Can (photo by the fearless Alan Cressler)

Of course this success has broad ramifications. The hymenoptera are everywhere in nature and they also play a huge part of human culture. Indeed the very name of this blog is a play on words between my surname and the noble art of aviculture.  Without the bees, we would not have much in the way of fruit or vegetables.  Not only would this be a disaster for human farming—just contemplate how many other creatures rely on those fruit!  Similarly the ants bulwark an entire portion of the ecosystem by scavenging the tidbits out of fields and forests.  Writing about the hymenoptera may be an itchy, antsy business but it is a well-merited study.  This group of insects is pivotal to life on dry-land as we know it.  The biblical promised land was one of milk and honey.  There would be no milk without mammals, but there would be no honey (and precious few mammals) without the hymenoptera.

A beekeeper completely covered with swarming honey bees in a “bee man” cantest in China

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