Tuesday, April 17, 2018

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!

Friday, April 13, 2018

Brown Canyon Hike, Buenos Aires National Wildlife Refuge

For Brown Canyon (you can still join in) on Saturday the 14th of April 2018, we will meet at 7:30 at the intersection of Ajo Way and Hw 286. At 7:40 sharp, we will go south on HW 286 to the turn-off into the preserve (right turn) around mile marker 20, meeting there at 8 am. . The guide will greet us and give a short talk, then take us into the preserve. Bring $5 cash for the guide! There are restrooms at beginning and end of the hike. Bring lots of water and a light lunch!
As the weather cooled down nicely, we are expecting a great, easy hike. Landscape, birds, bats, and bugs will not disappoint.

Brown Canyon is part of the Buenos Aires National Wildlife Refuge and only accessible as a group with a guide.

Tuesday, April 10, 2018

Ancylandrena Mining Bees in our back yard

Updated repost from 2014
 Our house is built on sand. It sits on a little mesa (elevation) consisting of soil that was excavated to put in the basement. Over the years I found out that we share this site with many sand loving, digging insects, tarantulas and scorpions. And please don't think that that is a problem. Some of these guys may even keep out others that we would like less.

The little dark parasitic bee, waiting close to the nest entrance
 Yesterday I was reading at the bedroom window when I noticed a dark little bee zigzagging and descending repeatedly out of sight under the window. Time to investigate.
When I got outside, she was resting on a flat rock. In the soil around it were several small, round holes about 5 mm in diameter. Another bee buzzed closer, circled, landed next to one of the holes and slipped inside.

A mining bee exiting the nest entrance
 This bee was larger, plumper, and lighter than the little observer. It stayed in the hole for a long time. While I was watching, two more bees arrived and crawled in. for over 10 min no bees left as far as I could see. Then the smaller bee flew up, circled shortly and also crawled into the hole. Several other bees of the bigger kind entered 5 other holes, all in an area of less than a square meter.  Eventually bees also exited the hole that I was watching, but too fast to get any good pictures. Peak activity seemed to be around 10 to 11 am.
Today I came better prepared. For example, I found a way to sit instead of crouching over the hole for what turned out to be long waiting times. So I got some video of the larger bees that clearly shows that several bees are using the same entrance and are under ground simultaneously. Incidentally, the little bee was inside during that time as well. This time I trapped her and three exiting larger bees to get a closer look. I had an idea by now that I was dealing with mining bees and a clepto-parasite, but I found that I didn't have these guys in my photo collection yet.

Ancylandrena sp. Doug Yanega det.
 Indoors, I put each bee into a white ceramic bowl and covered it with a clear plastic container. It took a while for them to calm down. If they had been beetles, they would have experienced a short cool-down in the fridge by now, but bees just don't look right when they are cold. So instead, I got the chance to take a few quick photos, some OK, some blurred and some out of focus, of each bee before she took off for the window. No harm done, they were easily coaxed back into the container.
John Ascher commented on BugGuide:
The expected species is A. larreae if creosote bush is blooming nearby (lots of it!)
The yellowish tan thoracic hairs are consistent with that species.
She should have a conspicuous yellow blister at e base of the mandible.

Hexepeolus rhodogyne, Doug Yanega det.
In the close-ups, the parasitic bee looked somewhat beat-up. Maybe her life as an uninvited guest was not quite as easy as it seems. But her visits in the nest, concurrent with those of several 'owners' did not seem to create any disturbance.

Several of my Flickr and facebook connections are bee specialists, so I posted the photos there and on BugGuide.

From Doug Yanega came the response:  "The latter is Hexepeolus rhodogyne, and it is a cleptoparasite in nests of Ancylandrena (the first bee). It wasn't until the 1990's that the host-parasite association of these taxa was confirmed, as I recall. The genus Hexepeolus contains only that one species".

John Ascher added a link to the 1994 paper: Biologies of the bee genera Ancylandrena (Andrenidae, Andreninae) and Hexepeolus (Apidae, Nomadinae) : and phylogenetic relationships of Ancylandrena based on its mature larva (Hymenoptera, Apoidea). American Museum novitates ; no. 3108

It turned out that BugGuide had an image of a mounted specimen of the parasite, but only an empty, prepared, page for the host. So I was able to fill in both with white backgound-life-close-ups and action in situ shots:

BugGuide Info Page

As for the species id, in Discover Life I found a description of a rare Tucson specialty, A. rozeni, but it would be difficult to identify it without comparative material:  A. rozeni - This is a rare species with records restricted to Arizona, specifically known from the Tuscon area - The male appears closest to that of A. larreae though slightly smaller, has a shorter clypeus, has shorter antennae, has smaller light markings in the paraocular area, is less densely pitted anteriorly on the scutum, hairs sparser in the anterior of the scutum, and has a greater proportion of dark hair on the upper areas of the head - The female appears most similar to that of A. timberlakei, although it may be differentiated by the presence of some degree of a tan or yellowish brown mound on the base of the mandible, a greater proportion of dark hairs in the upper areas of the head, the fact that all hairs anterior to the middle of the tegulae are white, and that there is a greater proportion of light-colored hairs on the scopa (2)
 Anyway, I preserved a specimen.

So to summarize, Ancylandrena is a mining bee. In spring males and females emerge from underground cells. They mate, and the females dig nest burrows in sandy soil. Mining bees collect pollen in the long hairs of the tibial scopa of the hind legs. (They do not  have a 'pollen basket' like honey bees and bumble bees). They construct small cells containing a ball of pollen mixed with nectar, upon which an egg is laid, before each cell is sealed. Although not social, several individuals seem to be sharing at least a nest entrance (Solitary, communal ground-nesting). As many insects do, they provide provisions for their offspring, but they are not around to guard the larvae while these are growing up. Clepto-parasites like the one I observed commonly make use of this arrangement to raise their own brood. Many of these clepto-parasites, like this one, are in the subfamily Nomadinae (Cuckoo Bees). They usually lack the hairs that are used by their relatives to collect and transport pollen. There are a number of strategies to get parasitic eggs into a provisioned nest. In this case the cleptoparasitic bee just followed the host bees to get her eggs into the brood chambers before they were closed. In Rozen's study several eggs of Hexepeolus rhodogyne were attached to the inner wall of the brood chambers while the larger egg of the host bee was sitting on the pollen ball. This explains why Hexepeolus was around for several days entering the same nest repeatedly: she had to access the chambers that were just in the right stage of construction.

PS: I was busy at an art show for three days, but when I checked again on Monday, 3/24/2014 there were still Ancylandrenas entering the same nest. I also found another nest about 60 meters south on a berm planted with cacti and creosote bushes.

Update April 2018: In the following years  I did not see these bees nesting again. But my observation and photos made it into a great new bee book 'The Bees in Your Backyard' by J S Wilson and O M Carril Princeton University Press 2016.

 In April 2018, on our neighbors' potted Aloe, I found a group of sleeping males most likely of the Ancylandrena species Ancylandrena rozeni. Id by John Ascher from my photos.
These guys lack the brown hair of the ones I photographed in 2014 and are silver-grey all over. No yellow blister under the mandibles.