A Closer Look: Nature All Around Us, April 2025

Photo: Humped Beewolf, Judy Gallagher

Judy Gallagher

April 2025

While researching something recently, I read that bees were descended from Crabronid or Square-headed Wasps, and I thought that the wasps would be an interesting topic for this column. 

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As you might have guessed, Square-headed Wasps are named for their large and square heads. They are solitary hunting wasps, and their prey includes aphids, bees, beetles, butterflies and moths, cicadas, cockroaches, crickets, flies, grasshoppers, hoppers, mantids, and spiders. Several species are kleptoparasitic, stealing prey captured by other wasps. The prey serves as live food for the wasp's larvae, and the adults mostly feed on nectar. There are more than 60 Square-headed Wasp species found in Virginia.

Eastern Cicada Killer with Cicada, Judy Gallagher

With a length of almost 2 inches, the Eastern Cicada Killer is one of our largest local wasps. As the name suggests, the female Cicada Killer catches cicadas, usually in flight, and stings them to keep them immobile. She digs a nest in the ground with 9 or 10 chambers, and provisions each chamber with one or more paralyzed cicadas. She then lays an egg on the cicadas. Male eggs get one cicada, but female eggs require two or more. Several females may use the same burrow, but they will each provision their own cells.

Velvet Ants or Mutillid Wasp females sometimes lay eggs in Cicada Killer nests. The Cicada Killer larva eats its cicada and grows and when it pupates, the Velvet Ant larva eats the Cicada Killer pupa. 

Horse Guard Wasp, Judy Gallagher

The Horse Guard Wasp is slightly smaller than the Eastern Cicada Killer, but it's still a big wasp. Its prey is horseflies. Female wasps fly around horses, often flying up and down the horses' legs, or even flying backward in front of the horse looking for horse flies. When she finds one, she stings it to paralyze it and puts it into burrows for her larvae. She actively hunts while the larva is growing, feeding it new horse flies as necessary, and resealing the nest between visits so that no parasites can enter the nest. The Horse Guard Wasp is an important biological control of horse flies, so if you're riding a horse and see something that looks like a hornet, please leave it alone and let the Horse Guard Wasp do its job. 

Organ-pipe Mud Dauber nest, Judy Gallagher

The Organ-pipe Mud Dauber is known for its mud nests that look like organ pipes. The female picks a nest site near a supply of mud. She picks up the mud with her mouthparts, rolls it into a ball, and then flies back to her nest site. She mixes the mud with her saliva, and then smears the mud mixture in long strips as you see above. 

Organ-pipe Mud Dauber with spider, Judy Gallagher

She then captures an orbweaving spider, stings it to paralyze it, and fills the nest with between five and twenty spiders. She mates at the nest, lays an egg on the spiders, then seals the nest with mud. While the female is hunting for spiders, the male sometimes guards the nest to prevent the spiders from being stolen or used by other parasitic wasps or flies

Humped Beewolf, Judy Gallagher

The Humped Beewolf preys on bees and wasps, with the most common prey being Sweat Bees. The adult female smears her nest with Streptomyces bacteria from glands in her antennae. The wasp larva uses the bacteria in its cocoon, and that protects it from fungi and bacteria in the soil. When a female wasp emerges from its cocoon, she picks up the bacteria from the cocoon, and the bacteria colonize her antennal glands, starting the cycle anew.  

Bicolored Mole Cricket Hunter, Judy Gallagher

The Bicolored Mole Cricket Hunter doesn't build a nest. The female stings a Mole Cricket to temporarily immobilize it, and lays an egg on the Mole Cricket on the thorax between its legs. The wasp first checks to ensure that there aren't any other wasp eggs there, and, if there are, she chews it off before laying her egg. When the wasp larva hatches, it slowly eats the Mole Cricket, even as the Mole Cricket continues to go about its business. 

One-toothed Sand Wasp, Judy Gallagher

The One-toothed Sand Wasp feeds its larva scavenged, dead and stolen prey. The only time that prey is alive is if it is stolen. 

It is intriguing that vegetarian Bees are a sister group to these magnificent predators. We should be grateful that we have so many Square-headed Wasps to keep other insect lines under control! 

View more of Judy’s articles on A Closer Look: Nature All Around Us (formerly Observations from Meadowood).