In the summer, bare soil can attract two scary-looking insects with threatening names: cicada killer and cow killer. Fortunately for people, they will sting only if handled aggressively. One's sting feels like a pinprick; the other's is quite painful.

Cicada killers, also known as giant gound hornets, save their venom for dog-day cicadas, the big green cicadas that appear every summer, damaging small tree branches as they slice them open to lay eggs. The female wasp patrols tree canopies in search of cicadas, which she paralyzes with a sting. She takes wing with her oversize prey and drags it down her four-foot-long nesting burrow. She places one or two cicadas in a chamber, lays an egg on the stunned insects and carefully seals the enclosure.

A wasp larva soon hatches to consume the cicadas, matures and spends the winter underground — unless it is itself eaten by the larva of a cow killer.

Cow killers, more often known as velvet ants, aren't ants; they are wingless female wasps that lay eggs on the pupae and mature larvae of cicada killers and other ground-nesting

Eastern velvet ant, Dasymutilla occidentalis. illustration by Patterson Clark

Eastern velvet ant or "cow killer"
Dasymutilla occidentalis
3/4 inch long

Cicada killer wasp, Sphecius speciosus. illustration by Patterson Clark

Cicada killer
Sphecius speciosus
2 inches long

solitary wasps and bees. When velvet ant larvae hatch, they consume their defenseless hosts.

Female velvet ants can deliver a powerful sting. It isn't venomous enough to kill a cow, but to a human, it feels as though it could. Female velvet ants are not aggressive and will attempt to escape if pursued. They must be cornered or stepped on before they will resort to stinging, and will even emit a warning squeak before doing so.

Likewise, female cicada killers won't sting unless forced to, and even then the sting is reported to be mild. Male cicada killers may

seem aggressive if they start flying around your head, but they are simply being territorial and are easily shooed away. They have no stingers.

Like their cicada-killer counterparts, male velvet ants are also stingless, but unlike female velvet ants, they have wings.

If gardeners aren't reassured by the knowledge that cicada killers and velvet ants pose little threat to people, they can fend off the insects by covering exposed ground with mulch or by seeding it with grass.

Sources: University of Florida, Journal of Entomological Science