Monday, April 22, 2013


The Iron Cross Blister Beetle (Tegrodera aloga) is a handsome beast, emerging in late spring in Sonoran Desert wherever there are soft sandy soils that support healthy colonies of ground-dwelling digger bees (Centris pallida). Yesterday evening we found a newly emerged swarm of beetles along the Central Arizona Project canal road north of Deem Hills Recreation Area. Thousands of beetles were feeding on fresh foliage of wheelscale saltbush (Atriplex elegans) at the edge of the road.

According to Carl Olson's guide to "50 Common Insects of the Southwest," these beetles have a complicated life cycle that depends on the bees and a healthy crop of palo verde flowers. Here is how Olson describes the scene:

"After mating, females seek palo verde trees in bud stage, lay eggs at the base of the buds, and then die. The eggs and buds develop together, eggs hatching when the flower opens. Larvae wait in flowers for native bees to arrive, hitch a ride back to the nest, where they stay, feeding on the juvenile bee and its provisions. They pupate in the nest and wait for next spring to emerge as adults."

This is just one more example of how everything is connected to everything else somehow.
Mingled in this little web of life, we also found a few Red-eared Blister Beetles wrestling with the Iron Cross Beetles. It was tough to tell if they were trying to mate with them, or having some kind of aggressive issue with their cousins. Red-ears have their own swarms earlier in the spring when brittle bush is in full bloom, so these few seemed to have missed the high season for mating with their own.  I suspect that this perennial urge is what got this one to pursue and mount a beetle of a different species, but probably with no success, since beetle mating paraphernalia, as with most insects, is highly specialized.

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