Yellow-banded Panurgine Bees

Image Credit: Bob Peterson

Yellow-banded Panurgine Bees (Andrenidae: Perdita, Nomadopsis)

In the Pacific Northwest, we have 35 species of these tiny gnat-sized bees, most of which are specialized feeders on only a single genus of plants. Nearly all of the species are characterized by some sort of bright yellow (or sometimes red) markings on the face, legs and abdominal segments. Occasionally some species are entirely yellow, red or black, and often with a weak metallic green iridescence on the head and thorax that is visible in the sunshine. Most of the other more than 650 species of the genus Perdita in North America are restricted to the deserts of the Southwest.

These diverse bees vary widely in their nesting habits. At least 1 species nests communally with a single burrow entrance and numerous individually-maintained side burrows. This nest is populated for several generations of bees. Other bees nest in fine Aeolian sand-dust, through which they must “swim” to find their cells below. It is a mystery how the pollen stays on their hind legs during this process and how they can locate their own cell; I personally have observed about a dozen females of the very rare Nomadopsis xenus “swimming” through the volcanic ash-dust at a site in Oregon. Some panurgine bees carry dry pollen attached to leg hairs in the way bees typically do, especially bees that specialize on the aster family. Generally, the hairs are quite sparse to non-existent in this group of bees. The species having basically no hairs glue pollen onto their legs with sticky nectar.

Perdita are tiny gnat-sized bees, usually only 3-5mm (=about 1/8th of an inch) long. Many of the most abundant species of Perdita have yellow on the legs, face and stripes across the abdomen. However, they come in a WIDE variety of color patterns. One frequent feature is a metallic green iridescence on the head and thorax.

Notice how all of the genera in this subfamily have extremely flattened abdomens. Many, but not all of the Panurginae subfamily have practically no hair on the legs, but instead glue the pollen mass to the legs with nectar. These tiny bees can carry quite a bit of pollen back in a single trip. Several hundred species of Perdita in California and Arizona are specialist-feeders on a wide variety of plant genera.

Nomadopsis are generally about twice the size of Perdita and they are nearly always specialists as well. This one is a specialist-feeder on the desert-dandelion (Malacothrix). Nomadopsis is unique in having extremely protracted copulation, and the 2 mates fly around in copula for several hours.