By Paul G. Johnson, Pinnacles National Park Wildlife Biologist
February 2018 - It’s fairly easy to imagine the basic life cycle of an aquatic insect living in a stream that flows year round: the adult insect lays eggs in the stream, the eggs hatch, the immature stages eat and grow, and then the adults emerge and continue the cycle. But how do insects carry out their life cycle in a stream that dries up for most of the year? What if the stream experiences summer flash floods, with the streambed being picked up and jumbled by the water?
Michael Bogan has been studying intermittent streams since 2003, and since 2014 at Pinnacles National Park. In order to better understand how aquatic insects survive periods of stream drying, he focused on a tiny winter-flying stonefly, Mesocapnia arizonensis. This species was known from only 22 locations in Arizona and New Mexico, but he found them at nearly 100 intermittent stream sites including Pinnacles National Park, a range extension of 500 miles.