Thursday, October 24, 2013

October Bugs on Burroweed

Bilbo, Frodo, Cody and Laika
On October 18th, I took our dogs for a walk along Santa Cruz River Path that begins behind the library in Cortaro, Arizona. At this time in autumn now even in Arizona the activity of insects and other arthropods is decreasing, mostly because it is getting really dry after this year's less than productive monsoon. But there are still several late blooming species of asteraceae that reliably attract their own communities of bugs.

Isocoma tenuisecta, Burroweed
Native to the Sonoran Desert, Isocoma tenuisecta, Burroweed, grows in dry, sunny, open, disturbed areas like roadsides, graded areas, and in overgrazed pastures and rangeland. I look for it in rural Marana where it can steal irrigation water from the cotton fields or live of run-off from roads.
Sphaenothecus bivittata
Two Cerambycid species can regularly be found: Sphaenothecus bivittata visits all late-blooming flowers and I always believed that this lively beetle with those extremely long antennae was just noshing pollen and nectar. But at a Patagonia art show my customers brought some to my booth that had been caught in flagranti: chewing holes into rose petals. I checked the literature: Among the known larval hosts are actually mesquite trees and - rose bushes.

Crossidius suturalis

Surprisingly, the much larger and stockier Crossidius suturalis is much more closely tied to the Burroweed. The little perennial is not only the meeting place for the adults who find their mates here, but the plants in the genus Isocoma are also the only known larval host for the species. 
This year Crossidius seemed rare around Tucson. It is possible that the small host plants are more affected by the drought than mesquite trees and roses.

Epicauta wheeleri and Epicauta sp.
 Among many grey blister beetles of the genus Epicauta that I don't even try to identify to species, there were a few with a bright orange pronotum. New to me, they turned out to be Epicauta wheeleri. Coincidentally, I had found them along the river path that originates at the Wheeler Taft Abbett Library. No relation, but easy to remember. I also know of a number of Wheelers that are entomologists with connections to Arizona, but the beetle was named by Holt in 1875...

Pygmy Blue, Checkered Skipper and American Snout
As it got warmer numerous butterflies descended on the burroweed. The Pygmy Blues find their larval host close by: Salt Bush planted along the river path by the Pima County gardeners who are doing a great job at using native shrubs for landscaping.
American Snout Butterflies were extremely abundant last fall - they must have migrated up from Mexico by the thousands. Not too many this year.

Apis melifera, Halictus ligatus, Agapostemon angelicus
Lots of introduced Honey Bees dominated the flowers while local Sweat Bee species showed up in much smaller numbers.

Lordotus sp. (?) and Poecilanthrax sp.
Where there are bees, there are usually also the brood-parasitic beeflies.  On my Burroweed patch, they were represented by several species, not all shown here.

Sinea diadema (Spined Assassin Bug) and Miturgidae (Prowling Spiders)
 Of course, there were also predators: One of the beeflies fell prey to a lurking assassin bug. A little Prowling Spider was hiding in its retreat until I investigated it too closely for her taste.

Conotelus mexicanus and Ripiphoris sp.
Both of the above photos show beetles: The black pegs that look more like seeds or may remind of rove beetles are actually Sap-loving beetles, Nitidulids. See the clubbed antennae?
The insect on the right is a female Wedge-shaped Beetle (Ripiphoridae) who does her best to look just like the bees that she intends to employ as foster parents for her brood. This species appears regularly in autumn on burroweed and is distinctly smaller than Ripiphorus vierecki that flies in April to lay its eggs on Desert Marigolds along this same River Path. If you are interested in the natural history of this group click here.

The Santa Cruz River Path in Cortaro is lined by new developments, sport fields, and small industry. It is a rather disturbed area, far from natural. But I still managed to find and photograph all the above insects and more while being pulled along by four impatient dogs.
So next week: a trip to a more natural area between Sonita in Santa Cruz County and Lochiel on the Mexican border, to check out blooming Desert Broom and Burrobrush (Chamisia), without dogs.


  1. The dusty looking bee's wings are incredible. What a great selection of bugs education as ever!

  2. Very nice. We had a very rich late summer/fall season with composites and insects visiting them, too. I need to keep an eye out for Ripiphorus. I think they are over here also.

  3. Great micro shots, Margarethe! I'll look closer from now on when I see bugs!