Big Rains Bring Bugs

See the bee in bottom left

See the bee in bottom left

Garden pipevine caterpillar

Garden pipevine caterpillar

Record amounts of rain create a big impact in an arid region, and not just in freeway underpasses and basements. The familiar trail where I walk was positively lush. Some plants I hardly recognized, so dressed were they in profusions of green. Seldom seen grasses grew in clumps on the desert floor, thrusting up and setting out seed heads in a water-fueled rush.

Insect eating birds – primarily black-tailed gnat catchers and verdins, worked busily among the foliage. Looking across the wash that dominates South Mountain’s Desert Classic Trail, I saw bugs massing above the green trees, backlit by the rising sun. Rain equals life, and near the bottom of the food chain, rain equals bugs.

A western spotted orb weaver spider hung her web from a block wall just above a hedge of Ruellia that buzzed with bees. The large moth trussed and motionless in her trap seemed to be looking out through the silken wrappings at me. A bee was also caught, with a leg tangled in the sticky web. It struggled vigorously, but in vain. The spider reached out and plucked at the web, which quivered along its length. Would she quickly wrap the bee as well? But she only strummed at her web until the bee broke free.

The sun was well up when I walked past again on my way home, and the spider and her meal cast a black shadow on the block wall. She crouched over the still form, feeding avidly.

In the garden I pushed aside a branch of Sonoran pipevine that snakes along the ground and discovered a large black caterpillar with red tubercles. This is the larval stage of the pipevine swallowtail. It feeds only on pipevine plants. The cautionary colors of black and red warn predators of powerful toxins that that the caterpillars ingest from the vine.

In early spring the adult swallowtail breaks out of the chrysalis as a large iridescent butterfly in shades of ebony and sapphire. Woe to birds that try to eat the butterfly; for all its changes in appearance, the swallowtail still harbors the toxins that the caterpillar recieved from its larval food plant. The butterfly is a dazzling visitor to gardens and roadsides where it pollinates many desert plants.

Read more about the pipevine swallowtail at Onelookout from March 2012.


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