The Beetles of Summer

Field Guide to Beetles of CaliforniaBeetles may be California’s most exuberant expression of life. Over 7000 species have been discovered in California and many more await discovery.

Beetles are fascinating to study because they have so many different colors, forms, and lifestyles. And there is no better time to explore the world of beetles than in the summer.

You may be startled, for instance, by a two-inch-long pine sawyer (Ergates spiculatus) buzzing around your campfire or lantern at night. This reddish-brown beetle is a member of a well named group of beetles called the Long-horned Beetles, and for good reason – the sawyer has antenna that are even longer than its body!

Or you may notice the crazed antics of Oregon tiger beetles (Cicindela oregona) running with incredible speed on the sand around your beach towel. These predaceous beetles use their long legs to chase down smaller prey along the open beaches of rivers and coasts. If you look closely you’ll notice that these odd beetles have huge eyes and brilliant iridescent colors on their upperparts.

It was recently discovered that tiger beetles have large eardrums hidden under their wingcovers that detect ultrasound produced by bats at night and by the wingbeats of predatory robber flies in the daytime; hearing the sounds of incoming predators gives tiger beetles a chance to escape being eaten themselves!

Many types of beetles are active during summer because they specialize on eating pollen, flower parts, or fruit. For example, one familiar beetle is the three-quarter-inch-long fig beetle (Cotinus mutabilis). Recognized by green upperparts that shimmer like an exotic jewel, this fruit-eating beetle has expanded from its native desert home into suburban neighborhoods where it finds lots of juicy fruits like figs. Look for the distinctive horn on its head that it uses like a can opener to peel back the tough skin of fruits.

As lowlands dry out in the withering heat of summer the main pulse of beetle activity follows the flowering season upslope into the mountains. July and August can be a fabulous time to find a great diversity of beetles in the mountains. Look for them in flowers and coming to lights at night.

Beetles are also common in the deserts of California, though desert beetles must adapt to very dry conditions. One of the most famous desert beetles is the stink beetle (Eleodes obscurus and other species). This one-inch-long shiny black beetle is commonly observed walking on open desert ground where its dark color stands out as a warning flag. When disturbed, the stink beetle does a “headstand” and lifts its rear end in the air. Like a small skunk, the beetle will squirt out a powerful dose of foul-smelling and highly irritating repellent – so watch out! This blast is effective against all predators except the grasshopper mouse (Onychomys torridus), who simply picks up the beetle, jabs its rear end into the ground and lets the beetle squirt its secretions harmlessly into the sand before eating it.

If these stories of beetles’ diverse lifestyles intrigue you, take some time this summer to watch beetles more closely. You will find beetles everywhere and they have many amazing tales to tell.

David Lukas, co-author of Sierra Nevada Natural History

One thought on “The Beetles of Summer

  1. Trying to get info on a black body, orange head beetle in Anza Borrego Desert State Park. We witnessed a large number of them on the ground mating, and in what one might conclude was a sexual orgy!

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