Moth Night

Moth Night at the Boyce Thompson Arboretum in Queen Creek last Saturday night attracted not only thousands of insects, but a few dozen naturalists and photographers ranging in age from 4 to 80. Using a pair of mercury vapor lamps mounted in front of a white sheet, entomologists from the Central Arizona Butterfly Association led the crowd in a frenzy of bug identification and admiration. 

The star of the show was a single patient Western poplar sphinx, with its nearly six inch wingspan and thick furry body. Surrounding this moth were dozens of white-lined sphinx, cholla moths, silk moths, five-spotted hawkmoths, tiny variegated tiger moths, and a handsome rustic sphinx, all fluttering in the bright lights. 

Western Poplar Sphinx (Pachysphinx occidentalis)

Beetles clamored to the scene by the dozens, including june beetles, blister beetles, mesquite beetles and click beetles. Cicadas, grasshoppers and bright green katydids also showed up. My favorite were the ant lion adults, elegant beasts with long lacy gray wings, and a pair of gracefully curved, thick, glossy antennae. Close encounters with three species of snakes and dozens of bark scorpions shining under black lights made this a 5-star event worth repeating in our own back yard. Next frivolous purchase: a mercury vapor lamp.

Ant Lion Lacewing 

Crack Climbing

It might seem like life is over once a pond dries up, but mud cracks are moist shady refuges for all kinds of life. Seeds take root, mosses grow and new toads explore these tiny canyons. 

Water Tigers

Water tigers live in ephemeral pools, devouring tadpoles, fairy shrimp, mosquito larvae and anything else it can grab with its jaws. These 2-3 inch long larvae of predaceous diving beetles are some of the most vicious predators in the desert suburbs, sucking the guts out of their prey and then disposing of the empty carcass. There are about a dozen species of predaceous diving beetles in North America, named Dytiscus in Latin, which means "great diver." 

My first encounter with a water tiger was here at a pond in Skunk Creek, just east of I-17 near the pedestrian bridge north of Jomax. Monsoon storms in late July this year revived myriads of critters that wait patiently in a dormant phase for water to return to the desert. When I first saw the dim outline of the larvae swimming in the murky water, I thought it was a small fish...but there are no fish in this usually dry wash. We captured one with a net and found that it had six jointed legs near its fearsome jaws, tipping us off to its identity as an insect. 

At rest, the water tiger will lift its rear end to the water surface to breathe through a pore or spiracle at the tip of its abdomen. Like their adult form, a large flat beetle, they are elegant and rapid swimmers. The larvae will pupate in the mud once the pond begins to dry, emerging as an adult when the next storm cycle revives the ponds it lives in. We never saw any adult diving beetles, but did witness plenty of water tigers prowling in the pools. 

Mexican Bird of Paradise

Mexican Bird of Paradise (Caesalpinia pulcherrima) lights up the Valley in mid-summer with flaming orange flowers. These plants in the Bean family (Fabaceae) have been part of world wide horticultural trade for so long that no one knows exactly where the first wild populations were discovered. Medicine men in Suriname have been using the plant for centuries, so this may be a clue to its origins.   It is also the national flower of Barbados, and displayed on the royal flag there, another clue to its native roots.

In the Phoenix area, Mexican Bird of Paradise provides welcome relief in the sometimes drab urban landscape, thriving along highways and industrial areas wherever there is a reliable drip system. Hummingbirds, carpenter bees and honeybees are frequent visitors to the flowers, serving as pollinators. The resulting bean pods produce hard seeds that are toxic enough to induce abortion in early term pregnancy, which was sometimes advised by the aforementioned South American medicine men. 

Beetlemania

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.

Spider Home

The leafy retreat of a female desert shrub spider (Diguetia canities) resembles a cocoon strung up by strands of web. Where these small spiders are abundant, you'll find their homes on nearly every shrub, especially bursage (Ambrosia spp.) and saltbush (Atriplex spp.). I found this one at Spur Cross Conservation Area attached to bursage, hanging over a  desert anemone (Anemone tuberosa). Perhaps the pollinators attracted to the anemone were her prey. Very clever, those spiders!

Yield to Brittlebush

If suburban sprawl has you worried that central Arizona may one day be completely overtaken by pavement, just remember that the life contained in Brittlebush (Encelia farinosa) seeds is far mightier than the Arizona Department of Transportation.  Able to sink roots into any gap in sidewalk, oblivious to vehicle exhaust and blossoming in the driest locations, Brittlebush will surely pioneer the restoration of this desert after the last drop of oil has been burned.

I joined this specimen thriving on an island in the middle of a round-about at Happy Valley Road and the I-17 yesterday, to document its life amidst the chaos of evening commuter traffic. I've been watching this plant grow for months, relieved each time I passed by that some ADOT crew hadn't doused it with herbicide or snatched it up by the roots. Now she is on her way to producing seed, and if all goes well, the island will be well populated by her progeny next spring!