Sources (in addition to main Arthropod page): Evans, Howard and Mary West-Eberhard, 1970, The Wasps, Ann Arbor: University of Michigan Press.
Wasps include a huge number of species, some 75,000 overall, most of which are parasitoid (lay their eggs on the larvae of other insects, and their larvae grow by consuming and thus killing their hosts), for example the Ichneumon Wasps (sometimes called "Ichneumon Flies" -- see an image below) use their very long ovipositor to pierce through bark to where larvae of other insects lie, to lay their own eggs there. These ovipositing Wasps include not only Ichneumons but also the Chalcid and others. From these are distinguished the so-called "true wasps", that is, the ones which are aculeate (the ovipositor -- egg-laying tube -- has become fully modified into a venom-injecting stinger used for defense and for paralyzing prey, while the egg is simply discharged directly from the body). True wasps, and their descendants, the ants) are known from the Cretaceous Period (100-80 million years ago), while their more recent offshoots appear in the later Cretaceous.
Here we will not try to order the huge array and very wide variety of Wasps systematically, but will simply present them as we encounter them. We start with the most conspicuous one of our area:
Tarantula Hawk (Pepsis heros, formosa or thisbe ?) (some 9 spp in U.S. deserts)
The Tarantula Hawk of our area, a "true wasp", is the largest (to nearly 3 inches in length) of some 4,000 species (worldwide) of spider-hunting wasps (the Pompilidae), which occur mostly in tropical and subtropical regions wherever spiders are found. The females fly low above-ground or even walk the ground scanning for prey by smell, favoring either Tarantulas or Trapdoor spiders. Typically the Hawk locates a burrow, probes the adjacent silk tempting the spider to emerge, then pierces the animal near the base of a leg to inject paralyzing venom with its stinger. It then drags the paralyzed spider to a burrow, lays a single egg on it, and seals the burrow where the larva will hatch, feed on the victim, and emerge the next spring.
Adults are nectar feeders, the one below shown favoring Yucca elata blossoms.
Below left: a clear view of the amber-to-reddish-orange-colored membranous wings (those of some species are black), with the dark, smoky border at the back edges; below right: the antennae of the Tarantula Hawk curl up in characteristic fashion (which often happens also after death; here perhaps to negotiate the narrow quarters of the Yucca elata flower clusters on which it is feeding); what looks like a protruding stinger at lower-left rear of the animal is actually the left rear leg.
Click on each image to enlarge it.
Below left: the antennae are again extended. Below right: the irridescent blue of the Tarantula Hawk's abdomen shows best in this image.
The brilliant colors of the Tarantula Hawk are aposematic, "conspicuous warning" of danger to those approaching this insect. While it is not aggressive toward non-spiders, its sting is described as the most painful of any North American insect, and no attempt should be made to handle one. (It's not lethal, but for those who have felt it that seems to be scant consolation.)
Digger Wasp (Chlorion sp.?)
Digger Wasps, members of the family Sphecidae, number some 8,000 species worldwide. The genus Chlorion is characterized by its metallic-green body and head. These are solitary species which parasitize crickets, dragging each one to a burrow in which it deposits a single egg. This one below, considerably smaller (< 2 inches long) than the Tarantula Hawk shown above, was however very similar in possessing aposematic coloring. It was photographed in August 2006 in lower Hot Springs Canyon following the unusually heavy rains of that month, when insects began to reappear in our area after a long period of scarcity.
Below, views of our most common wasp, which is strongly attracted to standing water in midsummer (late May 2004, temperature over 100 degrees F), and continues active into late fall: (Click on each image to enlarge it.)
Below, another view of this species of wasp, enjoying a flowering annual in August 2004:
This was a very tiny yellow wasp (size is shown in relation to a quarter), found dead in Lower Hot Springs Canyon in October of 2002: (Click on each image to enlarge it.)
Below left: this very tiny red wasp -- it looks like an Ichneumon -- was stalking the limbs of a Whitethorn Acacia tree which had been attacked by some kind of cocoon-spinning insect in May 2004; (Click on this image to enlarge it.)
Ichneumon Wasps (the term Ichneumon means "tracker" in Greek) are distinguished by having the abdomen joined to the thorax by a thin stalk, as shown here. Their "tracking" includes, in some species, drilling holes with the ovipositor down through layers of bark into larval nests of other species.
For views and commentary on our "Velvet Ants", see this link: Velvet Ants (Mutillid Wasps)