As you already know, I love bees. And what could be cuter than a sleeping bee? (Not much, as it turns out.) I often find little sleeping bees inside curled up petals, on the underside of thistle flower heads, or with their faces buried in flowers (I guess so that they can wake up to a sweet treat!). But in Australia, I was treated to a cluster of sleeping bees:
I found this big stag party on an outing with the illustrious photography, Mark Berkery. This is what is known as a sleeping aggregation (or sleeping cluster) of male bees. (Also, if you’re into adorable bees, check out this short, cute video. It just calls them “worker bees”, but they are actually males aggregating for the night.) Here is a description from “The Social Behavior of the Bees: A Comparative Study”, by Charles Michener:
“They consist of groups of males, rarely with a few females, which assemble in certain places to pass the night. There may be up to two or three hundred bees involved, usually with one species but occasionally mixed…The clusters are commonly on exposed stems, the bees clinging with their legs, often also with their mandibles. Some species also adopt a bizarre position, projecting rigidly at right angles from the twig or stem which they grasp only from the mandibles.”
But nobody knows why the males aggregate at night. There is some notion of a “predator dilution effect”, such that a predator must choose to feed on only one of the many available bees. But this kind of group selection argument is a hard sell among many ecologists.
Perhaps the most convincing explanation of this kind of behavior is the encounter dilution effect, proposed by Turner and Pitcher (1986). Here’s a clip from Wikipedia:
“In the detection component of the theory, it was suggested that potential prey might benefit by living together since a predator is less likely to chance upon a single group than a scattered distribution. In the attack component, it was thought that an attacking predator is less likely to eat a particular animal when a greater number of individuals are present. In sum, an individual has an advantage if it is in the larger of two groups, assuming that the probability of detection and attack does not increase disproportionately with the size of the group.”
The other beautiful sleeping bees that we found in the meadow were these Amegilla (here’s another cute article on them):
So we’re heading into winter in the northern hemisphere, but if you’re Australian, check out your meadows just before dusk! See if you can’t find some sleeping bees.