Hemipepsis ustulata is a species of tarantula hawk wasp native to the Southwestern United States. Tarantula hawks are a large, conspicuous family of long-legged wasps that prey on tarantulas. They use their long legs to grapple with their prey before paralyzing them with a powerful sting. Their stings are ranked as some of the most painful in the insect world according to the Schmidt sting pain index. They are solitary, displaying lekking territorial behavior in their mating rituals.
Description and identification
H. ustulata generally has a matte black body with rust-orange wings. It is among the largest of Hymenoptera, growing up to 5 cm in length. It is difficult to distinguish Hemipepsis from its Pepsis relatives. However, Pepsis tend to be a more metallic black with a deep-blue striped patterning. Since their biology and appearance is so similar, the only reliable way to tell them apart is by their wing venation patterns.
Distribution and habitat
H. ustulata is common in the arid climate of Southwestern United States, ranging from California through Arizona, New Mexico, and Texas, and as far north as Nevada, Oklahoma, and Kansas. Much of the fieldwork done on H. ustulata was performed in the Sonoran Desert near Phoenix, Arizona, by John Alcock. H. ustulata distribution overlaps with theraphosid spiders, which they parasitize to raise their young.The males, significantly smaller than females, possess more slender bodies and exhibit a more vibrant hue in their wings, serving as a visual cue during mating rituals Females, on the other hand, have robust bodies and their wings are slightly darker, a characteristic not commonly noted in existing literature. The wasp's antenna, with its unique curve and 12 segmented parts, provides an additional layer for identification, distinguishing it from other Pompilidae members. By including these specific morphological details, one can achieve a more comprehensive understanding and identification of Hemipepsis ustulata.
Life history
Parasitism
The tarantula hawk's namesake comes from its predation of tarantulas to raise their young. After mating, the female wasp seeks out a tarantula, either free-ranging or in its burrow. After grappling with the tarantula, the wasp delivers a powerful sting that paralyzes the tarantula, but keeps it alive. This allows the wasp to lay an egg that adheres to the spider's abdomen. One tarantula is provisioned per egg. The egg is about 5 mm long, gently curved, and creamy white in color. The wasp then drags the paralyzed tarantula along with the egg, sometimes up to 100 m, to a cavity or burrow to be sealed. This dugout can be either dug by the wasp or be the burrow of the paralyzed spider. When the larva hatches, it feeds on the spider's guts to completion, keeping the spider alive for as long as possible for peak freshness.
Larva
About three days after the egg is laid, the free end of the egg becomes glassy white. The grub chews its way out with its tiny, dark-tipped mandibles. Eventually, the eggshell splits, revealing the glistening, white, footless grub. The grub, still attached to the host tarantula by its tail end, arches over and digs into the tarantula's skin, creating a perforation aided by a dissolving fluid. After the grub is firmly attached by both its tail and head to the tarantula, it begins to suck the juices out of the tarantula's body. As it feeds, the larva grows, rapidly engorging itself on the tarantula and darkening in color. As it grows, it molts several times, casting off its head capsule and exoskeleton. After each molt, it resumes feeding, often through a new perforation. By the fourth instar, the tarantula's abdomen has collapsed slightly. At the fifth and last instar, the larva has developed a pair of stout, three-toothed mandibles to keep up with its feeding habits. The larva becomes muscular and mobile by this stage. It cuts a hole into the tarantula's carapace and thrust its head and thorax inside the host spider, continuing to feed ravenously. As it feeds, it hollows out the tarantula, up to the bases of the spider's hairy legs. At the beginning of this invasive assault, the tarantula finally expires. This entire process from egg to fifth instar takes around 35 days total.