Pepsis thisbe

Lucas, 1895

Thisbe's tarantula-hawk wasp

Pepsis thisbe is a large in the , commonly known as Thisbe's tarantula-hawk . Females are 32–44 mm in length with a dark body and orange . The exhibits pronounced : females have curly and a 7 mm , while males have straight antennae and lack stingers entirely. are nectarivorous, feeding primarily on flowers, but females hunt tarantulas as food for their . The species is distributed throughout the Southwest in desert areas.

Pepsis thisbe (5780826221) by Amante Darmanin from Malta. Used under a CC BY 2.0 license.

Pepsis thisbe 389182646 by Alicia Di Rado. Used under a CC BY 4.0 license.

Pepsini on Asclepias subverticillata by Paul Asman. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Pepsis thisbe: //ˈpɛp.sɪs ˈθɪz.bi//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from similar Pepsis by female shape (curly vs. straight in males) and male antennal 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 Southwest.

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Habitat

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

Distribution

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

Seasonality

Active during warmer months. 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.

Diet

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

Host Associations

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

Life Cycle

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

Behavior

Females hunt tarantulas primarily during morning and evening hours to avoid overheating. Hunting involves low over ground to detect burrows visually or chemically, or random landing with rapid antennal flicking and vibration while searching on foot. Upon locating an occupied burrow, the female cuts the curtain and enters, often evicting the for surface combat. After paralyzing the , females may exhibit lapping (feeding on wound fluids) depending on search time invested. Males aggregate in multi- '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 curled when agitated, accompanied by secretion of a distinctive odor.

Ecological Role

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

Human Relevance

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

Similar Taxa

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

More Details

Chemosensory Host Selection

Laboratory experiments demonstrate that P. thisbe females can discriminate between chemical cues from different tarantula , showing significantly greater response to Aphonopelma moderatum than to A. texense or novel cues. This selectivity correlates with field rates and may explain the disproportionate use of A. moderatum as a host despite comparable availability of alternative species.

Experience-Dependent Hunting Efficiency

Study of hunting in Trans-Pecos, Texas showed that time required for initial approach and paralyzation sequences decreases significantly with increasing encounter experience, indicating learned improvement in handling.

Host Sex Bias

Field data from southern Texas indicate that 81% of paralyzed A. moderatum with attached were female , suggesting possible sex-biased selection or differential vulnerability.