Thursday, August 2, 2012

Cicada killers are Wimps

Spread the word – Cicada killers are wimps! Unfortunately, because of their size and the fact that they often live in lawns and landscapes close to where people live, cicada killers evoke a great deal of anxiety.  These wasps are huge and look very much like oversized yellow jackets but they have some very important differences. First, cicada killers are not social wasps that build colonies and protect their queens.  Because they have no colony or queen to protect, they are not aggressive and have no reason to sting people.

Cicada killers are one of the largest wasps that burrow into the ground in this area.  At first glance, they are a very large, ominous looking wasp resembling a hornet or yellow jacket and evoke a good deal of fear. However, most of the wasps encountered are males, patrolling the nesting area. They may fly about, dive bomb, or even hover in front of, but they cannot sting people. They do not possess a stinger.
Females do not defend their burrows, and will sting only if handled. Female cicada killers dig burrows in well drained, light textured soil, typically in an area with full sunlight. The 1½ inch diameter opening leads into an oblique tunnel that runs for 12-18 inches and reaches a depth of 6-10 inches. The female completes and stocks up to four cells, each containing from one to three paralyzed cicadas on which eggs are laid. When eggs hatch the larvae bore into and feed on the cicada. Secondary tunnels are often built off the primary tunnel; thus each female may rear up to 16 larvae in a burrow.

Cicada killer wasps are beneficial and do not pose danger in most cases.  When possible they should be left alone. 

The larvae pass the winter in their burrows and emerge the next July as adults. Between late July and mid August, these new adults emerge, mate and the female digs new soil burrows, stocks them with cicadas, and the cycle is repeated. Adults usually die by mid September.
On occasion a large nesting aggregation can result in many holes and unsightly mounds of soil in a small area of a yard or garden. Control of cicada killers is safely and most effectively done by placing a small amount of 5% carbaryl (Sevin) dust down into the soil tunnel. For a large nesting aggregation, the area can be sprayed. In both cases, the tunnel entrances should be left open.
In most cases, Cicada killer wasps are beneficial and do not pose danger.  When possible they should be left alone.  Education is the single best strategy to help people deal with cicada killers.  Teach people that they may look dangerous but in reality – they are wimps.

Timothy Gibb, Department of Entomology, Purdue University


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October 22, 2012 at 3:51 AM

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