Photo by Paul G. Johnson II.

Western pondhawk dragonfly.

Although at first glance Pinnacles National Monument may appear to be a vast arid landscape, a little exploration will reveal occasional welcome water sources. Streams, springs, ponds, and the Bear Gulch Reservoir support an abundance of life. In 2001, park biologists began a two-year project to inventory the aquatic macroinvertebrates of Pinnacles. The goal of the project was to collect and identify every species of worm, snail, crustacean, arachnid, and insect that lives in or around water and can be seen with the naked eye.

One conspicuous group of aquatic macroinvertebrates is the dragonflies and damselflies, collectively called odonates. These familiar insects can be seen darting about almost anywhere there is fresh water. So far, twenty-four species of dragonflies and sixteen species of damselflies have been identified from Pinnacles, with more almost certainly to be found.

Adult odonates are voracious predators, catching flying insects with their mouths or with their spiny legs held out like a basket. One look at their huge eyes will tell you that they have great eyesight for spotting their prey. Unlike other insects, their front and hind wings beat in opposite directions, giving them excellent maneuverability in flight. They are also among the fastest flying insects.

Many odonates live for just a few weeks as adults. They have only this short time to reproduce, so when they are not resting or feeding they are often involved in reproductive activities. A male spends much of the day either perching and keeping a watchful eye over his territory or patrolling back and forth through it. Females lay hundreds or thousands of eggs by poking them into the bottom of shallow streams or into plant stems, dipping them onto the water surface, or dropping them from the air into the water or onto moist soil. After mating, a male will often guard a female or remain attached to her as she lays her eggs, in order to ensure that she does not mate again.

Young odonates (naiads) live in water and are wingless, barely resembling their parents. They are also voracious predators, eating small invertebrates and even fish and tadpoles. Some live among aquatic plants, others burrow in sand or mud, and others sprawl in dead leaves on the stream or pond bottom. This latter type is often hairy so that mud and bits of sticks and leaves cling to them for camouflage.

You can sometimes see odonate naiads by looking in shallow water. On plants and rocks near water you are likely to see shed exoskeletons left behind from naiads that transformed into adults. If you happen to see an adult emerging from an exoskeleton, please do not disturb it. It will be very fragile until its wings and body have dried and hardened. If you wait patiently, you may get to watch its first flight!

Watching adult odonates can provide hours of entertainment. Their aerial acrobatics are astounding. With a little study and practice you can often decipher the reasons behind their behavior: chasing prey, laying eggs, drinking water, guarding a mate, patrolling a territory, regulating body temperature... Their bright colors make many species easy to identify, but keep in mind that males and females of the same species may look quite different. If two dragonflies are interacting, they are likely to be the same species. This is not as likely for damselflies.

If you see a species at Pinnacles that is not on our list, please let us know as soon as possible so that we can attempt to confirm the sighting. Give us information on date, time, location, and habitat. Include a photograph if possible. You may give the information to a park ranger or contact Paul Johnson at (831) 389-4486 ext. 271 or e-mail us. Please remember that in order to protect the odonates and other natural features of Pinnacles National Monument, no collecting is allowed.

References:

-Biggs, Kathy. 2000. Common Dragonflies of California, A Beginner’s Pocket Guide. Azalea Creek Publishing.
-Dunkle, Sidney. 2000. Dragonflies Through Binoculars, A Field Guide to Dragonflies of North America. Oxford University Press.
-Manolis, Tim. 2003. Dragonflies and Damselflies of California. University of California Press.
-Merritt, Richard, and Kenneth Cummins (Eds.) 1996. An Introduction to the Aquatic Insects of North America. Kendall/Hunt Publishing Company.

Related Information

California Dragonflies and Damselflies