Monday, March 12, 2012
Brittle Bush Bee Heaven
Last year a late, very strong freeze kept many Brittle Bushes in the Tucson Mountains from blooming. In March it felt as if all kinds of interesting bees had found their way into our protected backyard habitat. Of course, the distances that these small endemic bees travel are really quite small. But for whatever reason, my BugGuide entries for last March show dozens more species than I'm finding this year.
So far I saw no Colletes (left), few Anthophora (middle) even though the Penstemons are already past their prime, and the long horned Eucera (right) are still missing. While a Leaf-cutter bee in Saguaro National Park volunteered to star in a video, I hardly see any in our backyard. The cactus bee Diadasia will certainly show up once the cacti are in flower.
Lasioglossum sisymbrii (left) is here, and several Agapostemon species (middle and right), some of them very pretty and shiny green. Some Agapostemons had been invading our living room windows throughout the winter to the delight of a resident Kukulcania Spider.
In the early morning hours, Honey Bees seem to be taking advantage of their greater body mass and thermoregulated hives: they visit the Brittle Bushes when it is still rather cool. (this observation is contrary to the info in BugGuide - Maybe the remarks there refer to climate conditions different from Arizona's)
Around noon, by far the dominant genus in our backyard is Adrena, recognizable by their furry faces (facial fovea). I'm seeing at least 2 morpho-species, a brown one and one with a partly rust-colored abdomen. The females collect pollen into tibial brushes similar to those of honey bees. They will take the pollen to their solitary ground nests. Each egg will be laid on its own ball of pollen and sealed in its own chamber. Our sandy, dry soil is just perfect for these Mining Bees.
Adrena males are smaller and more narrowly built, with the light face that is characteristic for many male bees. They spend their time hovering and zigzagging over the flowers. They rarely land to refuel with nectar. All bees that are quietly collecting attract their attention. Although pheromones prevent greater confusion, these eager males zoom in on anything from Agapostemon to Honey Bee. It's quite annoying if you are trying to photograph.
If they find a conspecific female they grab it, and in most cases a struggle ensues which usually makes both bees fall off the flower and out of focus. To get photos I finally just focused on an attractive female and waited for the males to show and that worked like a charm.
The abundance of Adrena females also drew another visitor with a quite different agenda. Today I found my first Nomada Bee and promptly misidentified it as a wasp. Nomadas got their name from the fact that they have no nest of their own. Instead, they are clepto-parasitic cuckoo bees, depositing their eggs into the nests of the other bees, mostly in the genus Adrena.