- Photo(s): Ned Harris, www.flickr.com/photos/ned_harris
Tarantula hawks are easily recognized by their robust, iridescent blue-black bodies and (usually) shiny orange wings. Also known as Pepsis Wasps, these insects deliver the most painful sting of any North American insect. Fortunately they do not often sting humans. They are nectar feeders and are most active in the summer.
Fifteen species of pepsis wasps (aka tarantula hawks) are found in the U.S., mostly in the southwest. Several species occur in the Sonoran Desert. Tarantula hawks are easily recognized by their robust, iridescent blue-black bodies and (usually) shiny orange wings. In some of the species the wings may be blue-black instead of orange. Tarantula hawks range in body length from about half an inch to over two inches, with males considerably smaller than females. The females have curled antennae that distinguish them from the males. It is quite easy to identify an insect as a pepsis wasp but it is very difficult to distinguish the different species in the field.
These wasps are most easily seen around blossoms during the summer. Both male and female pepsis wasps drink nectar from flowers. I have seen them many times in my back yard, especially on Milkweeds. During the summer months, once the female tarantula hawk has mated she searches the ground for tarantulas. She needs to capture a tarantula for each egg she will lay. This can be a challenge because tarantula hawks are diurnal and tarantulas are nocturnal. The female wasps go into a searching mode running wildly over the ground using their eyes and sense of smell to locate a tarantula. Sometimes they locate a burrow of a tarantula. Tarantulas close off their burrow with silk strands and the wasps will vibrate the silk strands to fool the tarantula into coming out expecting prey at the entrance. When the tarantula emerges from the burrow, the wasp will provoke the spider by prodding it with her antennae. If the tarantula rears up on it’s legs, the wasp will deliver a sting into the nerve ganglia in the underside of the spider’s cephalothorax. She then drags the spider back to it’s burrow or another sheltered location. Next she lays a single egg on the paralyzed, but still alive, tarantula. This egg hatches in 3 to 4 days, and the newly emerged larva then attaches to the spider’s abdomen with its sharp mandibles. It feeds on liquids from the tarantula for its first four growth stages. In its fifth stage, the larva chews into the tarantula and consumes much of the innards, killing the spider. The larva, now more than two inches long, spins a cocoon and pupates inside. It molts through several instars before pupating. Pupation lasts 2-3 weeks, after which the new adult tarantula hawk emerges.
I learned this fascinating life cycle story during my naturalist training in 2005. For 13 years I always carried a camera during my visits to the canyon. Finally on August 29th of this year I was walking down the Bear Canyon trail when I noticed a tourist taking a photo with his cell phone. I walked over and soon saw a tarantula and a nearby tarantula hawk. I was thrilled to finally capture images of this behavior.