Centris Bees and White Ratanay in the Tucson Mountains

Krameria grayi – White Ratany is a grayish inconspicuous desert bush that grows in the lower elevation of the Tucson Mountains  Even when it's blooming, they are not very showy, though the single flowers and later the heart shaped seed pods are very pretty and intricate.

But right now, during their blooming season the bushes draw attention not through their looks but by the noise coming from them. Loud, deep buzzing, very sonorous, very different from the higher sound of Honey Bees.

Big Centris bees are coming and going, sometimes hovering with a strange wiggling motion, sometimes landing in the sand nearby - seemingly just resting.

These New World bees range with 250 species from Kansas to Argentina, and here around the Tucson Mountains I have found at least 3 species. Females of these bees possess adaptations for carrying floral oils rather than (or in addition to) pollen or nectar. According to Wikipedia, they visit mainly plants of the family Malpighiaceae to collect oil, but also Plantaginaceae, Calceolariaceae, Krameriaceae and others. Yesterday, they were definitely concentrating on that one blooming Kramericea, the Ratanay.

Some also visited Janusia, Fam. Malpighiaceae. I did not know the family of this strange vine, but obviously I can rely on the good senses of the bees and in this case Wikipedia (I think I know who is the careful editor of these bee entries).

The Centris bees  completely ignored a desert lavender bush in direct proximity. These flowers were later in the day extremely popular, but with honey bees.

Centris Subgenus Paracentris, Oil-Diggers and Desert-Diggers, Female, could be C. cockerelli or atripes

I have watched Centris pallida  dig tunnels and nesting chambers into loose sand and J. Alcock describes the same for another sympatrically occurring Sonoran Desert Centris, C. rhodopus. So I expect this Centris bee to behave similarly. 
I asked Entomologist and pollination expert Doug Yanega how the oil is used in the nest to rear the larvae. Here is his answer:

'The nest cells are vertical and they have a lining that prevents the oil seeping into the soil, and the bees just scrape off the liquid (which is rather viscous) into the cell.
Once they have a good pool, they float an egg on top and seal it. There are numerous bee genera that do this worldwide, but in the US I think only Macropis and Centris, IIRC.

P.S. Today I found this C. cockerelli  on our neighbor's hybrid (Desert Museum) Palo Verde. There is no sign of C. pallida yet, but most of the foothills paloverdes are not blooming yet around Picture Rocks. I just learned from Doug Yanega that there are no oils in Parkinsonia - just nectar that the bees need to feed themselves. I guessed that already because I often see male Centris on those flowers.

As for the species identification of the Rantanay Centris: One suggestion was C. caesalpinia, but they have red eyes, which mine did not.  Not C. rhodofus because they have red eyes and legs. Mine look like C. cockerelli, except that those should have yellow faces, and mine have a reddish orange clypeus. But:
 John Ascher When all else fails, consult the literature! Turns out that there is a western form in CA and AZ of C. cockerelli with a reddish yellow clypeus and an eastern form form in TX with a white to yellowish clypeus intergrading in NM. I had forgotten about this. So C. cockerelli is likely correct. Sorry for the confusion. At least we learned something (if nothing else, to consult the literature rather then rely on memory!)
 So: western form of Centris cockerelli!

First sightings for this year

Yes, I know. The first of May is a funny date to start this attempt to record some phenological data for our area in SE Arizona. I think there is still enough of my northern European upbringing in me to feel that this date is special. I will try to begin every month with a little summary of the season's best observations that haven't made it into a blog of their own.

So here goes:

Iron Cross Beetles, Tegrodera aloga, in Sabino Canyon, April 27 2013, Photo by Ned Harris

All week in Sabino Canyon we found big groups of mating and feeding Iron Cross Beetles. Most of them congregated around nearly dried up Whooly Star plants.

Gambel's Quail, Callipepla gambelii, with chicks

Yesterday, April 30, the first very tiny baby Gambel's Quail. The parents made such a ruckus that I actually went and checked whether it was a snake alarm. But eventually they coaxed some very young chicks out of the brush, so I knew what the excitement was about.

Centris pallida on Ironwood and Centris rhodopus on White Ratanay

The first Saguaros bloom and the first Ironwoods are covered in pink. The deep humm of Centris bees can be heard from a distance. Centri pallida visits the leguminous trees, the flowers of the White Ratany and Creosote are attracting the darker Centris rhodopus.

Mesquite flowers in Saguaro National Park West are covered in mating Netwing Beetles of the genus Lucaina, and the first Lycus sanguinea showed up, too. No group leks for this species.

Creosote Bush Katydid, Insara covilleae, nymph

I also found a very camouflaged last instar nymph of the Creosote Bush Katydid, Insara covilleae, feeding, as it should, on creosote leaves.

Enallagma civile (Familiar Bluet)

At a pond at the Desert Museum, another nymph had just left its old skin and its former element behind to spread its wings as a Damsel Fly. But first it had to patiently wait until its teneral paleness transformed itself into the beautiful color of an adult Bluet.

Today: May 1, the first Lesser Nighthawk swooped out of his hiding spot in a Palo Verde in the State Land. In the evening they were courting, a pair gracefully dancing over our backyard while continuously making a sound like a melodious purr.

White-throated Swifts Aeronautes saxatalis) adapted from a photo by Alexander Viduetski

 In the morning four White-throated Swifts were also very active over our yard, but their shrill, twittering calls drove the dogs crazy and their ballet soon deteriorated into a wing-on-wing battle, with two of them (a couple, two males??) tumbling repeatedly all the way to the ground. I had never before seen them do anything but catch bugs so high above that they seemed to belong to another reality...not earthbound as they suddenly seemed. The things we do for sex...

Prickly Pear Cacti and Chollas are in full bloom. The flowers are full of Diadasia bees, the digger bees that are specialised on cactus flowers.

Little swarm of feral, Africanized Honey Bees. The wandering swarm (left) is very peaceful and approachable. The one that found a cavity in the saguaro will build a hive there and then may get aggressively territorial

This year we seem to have fewer feral Honey Bees than usual. Our Africanized version is not as freeze tolerant as the European stock (that's why they never became a problem in Europe and further north in the US, just here in the Southwest where the winters are usually warm). The species is otherwise very robust and there are enough bees left to increasetheir population again to compete with our native bees.

Male Black-tailed Gnatcatcher

From my studio window I'm watching the antics of four or five fledgling Black-tailed Gnatcatchers. They are probably learning to glean the Palo Verde tree for small caterpillars of the Palo Verde Looper.

Palo Verde Looper, Faculta inequalis

The adult moths are coming to my black-light at night where they are eagerly awaited by several small Red-spotted Toads who were joined last night by the first huge Sonoran Desert Toad.

Western Banded Gecko, Coleonyx variegatus

I have never seen a Banded Gecko this big and colorful. I think he must be in his mating-season best!