The dog days of summer wouldn't be the same without the power-tool-like screeching of cicadas—or the unsettling appearance of their predators, the cicada killers. Among the biggest wasps in America at up to 2 inches long, these insects are understandably alarming. Even their coloration seems menacing: black bodies with light yellow abdominal markings and rust-colored heads, thoraxes, and wings. But with insects, appearances can deceive. In reality, cicada killers are gentle giants that help to moderate the cicada population. Female cicada killers won't sting unless stepped on or otherwise threatened, and males lack stingers entirely.
The eastern cicada killer, Sphecius speciosus, is found east of the Rocky Mountains. Similar species are native to the western United States and Mexico. Emerging from the ground beginning in June, adult cicada killers quickly start excavating new burrows 6 to 12 inches deep, showing preference for sandy or loose soil in full sun and with little vegetation. While the smaller male cicada killers hover around a specific area, driving away rival insects, the females go hunting. Upon finding a cicada, the female wasp stings, and thereby paralyzes, its prey. Then, in a herculean effort, the wasp lugs the cicada, often twice its weight, back to the burrow and deposits an egg on it. Burrows may contain several cells, each holding one to three cicada victims, which serve as food for larvae that soon hatch from the eggs. The wasp larvae eat cicadas for approximately 2 weeks, later spending winter in their underground homes and pupating in spring. Adults subsist on nectar and tree sap and die by mid-autumn. There is one generation per year.
Cicadas are in no short supply, and too many can lead to twig dieback on trees and shrubs. Cicada killers play an important role not only in controlling the cicada population but also in aerating soil by creating burrows. Because they prefer bare soil, their burrowing is a result of turf decline, not the cause of it. Still, instead of applauding the industrious cicada killers, homeowners too often give in to knee-jerk reactions and try to exterminate them.
Originally published in Organic Gardening Magazine August/September 2013.