Pepsis thisbe

Distinguished from similar Pepsis species by female antennae shape (curly vs. straight in males) and male antennal segment count. Males of P. thisbe have 12 antennal segments. May be confused with P. grossa, but P. grossa females average larger (43 mm) and males have 12 antennal segments (unique to that species). P. thisbe is generally smaller than P. grossa with different geographic distribution patterns. The orange-winged form is most common in the American Southwest.

Desert areas of the American Southwest, including creosote scrub, mesquite-acacia woodlands, and arid grasslands. Found in areas with suitable tarantula host populations and flowering nectar sources.

Throughout the American Southwest, including western Texas, southern New Mexico, and southeastern Arizona. Field studies have documented populations in Trans-Pecos, Texas and Zapata County, southern Texas. The species ranges across arid and semi-arid regions where tarantula hosts and flowering plants are present.

Active during warmer months. Adults observed on flowers and at nectar sources. Hunting activity by females shows a bimodal daily pattern with peaks between 0800–0959 and 1600–1759 hours; activity declines when ambient temperatures exceed 38°C and drops abruptly after 1800 hours.

Adults are nectarivorous, feeding on flower nectar. Milkweed (Asclepias spp.) is a preferred nectar source, but adults have been observed on creosote bush, blue palo verde, eucalyptus, mesquites, acacias, and burroweed (Isocoma tenuisecta). Females also drink water at puddle edges.

• Aphonopelma moderatum - primary hostTheraphosidae tarantula; over 91.2% of field-collected P. thisbe larvae were attached to this species in southern Texas, despite similar abundance with alternative host
• Aphonopelma texense - secondary hostTheraphosidae tarantula; only 8% of larvae attached to this species in field collections from southern Texas

Females paralyze tarantula hosts with a sting to the nerve center, typically through the intersegmental membrane between the sternum and coxa of the first leg (>80% of stings). The paralyzed spider is dragged to a burrow—often the spider's own—and a single egg is laid on the host. The larva consumes the living but paralyzed spider, progressing through instars with ontogenetic changes in feeding patterns. Development from egg to adult requires approximately 41 days at 30°C and 70% relative humidity; eggs and larvae do not survive at 10% RH. The larva eventually spins a silken cocoon, pupates, and emerges as an adult.

Females hunt tarantulas primarily during morning and evening hours to avoid overheating. Hunting involves low flight over ground to detect burrows visually or chemically, or random landing with rapid antennal flicking and wing vibration while searching on foot. Upon locating an occupied burrow, the female cuts the silk curtain and enters, often evicting the spider for surface combat. After paralyzing the host, females may exhibit lapping behavior (feeding on wound fluids) depending on search time invested. Males aggregate in multi-species 'bachelor parties' on trees during midday heat and overnight, sometimes performing hill-topping behavior to intercept females. Both sexes adopt a threat posture with wings splayed and abdomen curled when agitated, accompanied by secretion of a distinctive odor.

Specialized parasitoid of tarantula spiders, regulating host populations. As a large nectar-feeding insect, likely contributes to pollination of desert flowers. The species' abundance suggests substantial tarantula populations in the Sonoran Desert and related arid ecosystems.

Notable for possessing one of the most painful insect stings known, rated near the top of the Schmidt sting pain index. However, the venom causes no tissue damage and pain subsides within approximately three minutes. Stings are not life-threatening unless the victim has allergic reactions. The species is generally placid unless provoked and is valued by entomologists and naturalists for its impressive size and coloration.

• Pepsis grossaLarger size (females average 43 mm vs. 32–44 mm for P. thisbe); males have 12 antennal segments (unique among Pepsis); exhibits both orange-winged and black-winged morphs; geographic range extends further east to Missouri and Arkansas
• Pepsis mexicanaVery similar appearance but smaller than P. grossa; males have fewer than 12 antennal segments; geographic distribution overlaps in parts of the Southwest
• Hemipepsis ustulataDifferent genus of tarantula hawk wasp; similar ecology and behavior but taxonomically distinct

• spider wasp
• tarantula hawk
• parasitoid
• desert insect
• painful sting
• sexual dimorphism
• Pompilidae
• theraphosid host

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• Bug Eric: Wasp Wednesday: Pepsis grossa
• Belostomatidae | Beetles In The Bush
• Arthropoda | Beetles In The Bush | Page 7
• Bug Eric: Tarantula Hawks
• Behavioral Responses of Pepsis thisbe (Hymenoptera: Pompilidae) to Chemosensory Cues Associated with Host Spiders
• The Biology of the Spider Wasp, Pepsis Thisbe (Hymenoptera:Pompilidae) From Trans Pecos, Texas. II. Temporal Patterns ofActivity and Hunting Behavior With Special Reference to theEffects of Experience
• The Biology of the Spider Wasp Pepsis Thisbe (Hymenoptera: Pompilidae) From Trans Pecos, Texas. I. Adult Morphometrics, Larval Development and the Ontogeny of Larval Feeding Patterns