Genus Pepsis - Tarantula-hawk Wasps

Classification

Other Common Names

Tarantula Wasps

Synonyms and other taxonomic changes

A number of former species names have been synonymized under new names in the most recent revision of the genus by Vardy (2002-2005).(1) Listed below are the former names as they appeared in main earlier references by Hurd (1952),(2) Townes (1957),(3) Krombein (1979),(4) and others, followed by their current names, and where the taxa are discussed in the three-part work of Vardy:(1)

Explanation of Names

Pepsis Fabricius, 1804

Numbers

14 spp. in our area arranged into 7 species groups(1)(4); 133 total described species in 19 species groups across the Americas(1)

1. P. aquila: s. AZ & NM

2. P. basifusca: TX north to KS, west to s. CA

3. P. cassiope: AZ, CA, & TX

4. P. chrysothemis: TX & OK west to CA

5. P. grossa (f. "grossa"): MO, TX, & KS west to AZ & NV; (f. "pattoni"): AZ, CA, NM

6. P. marginata: s. FL

7. P. menechma (f. "menechma"): PA west to KS, south to FL & TX; (f. "cerberus"): AZ, KS, TX

8. P. mexicana: TX to s. CA

9. P. mildei: TX north to KS, west to CA

10. P. pallidolimbata: TX, OK, & KS west to s. CA

11. P. ruficornis: s. FL

12. P. sommeri: s. TX

13. P. terminata: s. AZ

14. P. thisbe: TX north to NE, west to CA

rubra group: P. chrysothemis, P. mexicana, P. pallidolimbata, P. thisbe

grossa group: P. grossa

elevata group: P. aquila, P. marginata, P. terminata

brevicornis group: P. cassiope

inclyta group: P. sommeri

menechma group: P. basifusca, P. menechma

ruficornis group: P. mildei, P. ruficornis

Size

14-40 (50?) mm

Identification

Overview of Genus

Large "metallic-sheened" blue-black to greenish wasps, most with orange wings. Some species have orange antennae. Typically, females hold their antennae curled (in an arc of a half-circle or more), while males hold theirs more straight. Among the largest and most easily recognized genera of spider wasps, only Hemipepsis is easily confused, but orange-winged individuals of Entypus are superficially similar. This genus can be recognized by the characters given below:

Large size, to 40 mm+. With blue, blue-green, or blue-violet iridescence. Only rarely does Hemipepsis have iridescence and most in that genus lack it completely, or if it is present it is very vague. Only rarely does Entypus reach the size listed above.

Wing venation is very important for identification of Pepsis especially distinction between Pepsis and Hemipepsis. Those characters are as follows:

Marginal cell apically separated from the costal margin, making that cell appear very rounded

First recurrent vein meeting the second submarginal cell at its basal third, thus making the first discoidal cell rather short and rounded. In Hemipepsis the first recurrent vein meets the second submarginal cell at its apical one-third or is occasionally interstitial with the second transervse cubital vein, thus making the first discoidal cell rather long and pointed

Subcircular irregularity at the base of the first discoidal cell not as developed as in Hemipepsis

Pulvillar pad and comb in Pepsis is rather weak, the pulvillar pad about half as wide as the apical tarsal segment. The pulvillar comb consists of eight to ten weak setulae. In Hemipepsis this character is well developed with a large pulvillar pad that is approximately three-quarters the width of the apical tarsal segment and the puvillar comb that consists of 14-40 strong setulae.

Overview of Species

Species follow the following trends based on antennal and wing coloration in our area:

Black antennae; black wings: P. grossa ("pattoni" form) & P. mexicana

Black antennae; orange wings: P. basifusca, P. chrysothemis, P. grossa ("grossa" form), P. marginata, P. menechma ("cerberus" form), P. mildei (some AZ populations); P. pallidolimbata, & P. thisbe

Orange antennae; black wings: P. menechma ("menechma" form), P. ruficornis, & P. terminata (apical 2-3 segments)

Orange antennae; orange wings: P. aquila, P. cassiope, P. mildei, P. sommeri

Range

Mostly southwest US, east to Kansas. Only three species occur in the east, the most common and wide-ranging one being P. menechma...the other two, P. marginata and P. ruficornis (= saphirus), have been recorded from south Florida (possibly as accidentals from the West Indies?). The genus also extends far south into neotropics, where it is much more speciose.

Habitat

Open areas, deserts

Season

mostly Apr-Nov in sw US (BG data)

Food

Larvae feed on tarantula and some other large spiders. Adults take nectar, and are particularly fond of milkweed (genus Asclepias).

Life Cycle

Mating takes place on flowers, or sometimes near a "hilltop", such as a large cactus, defended by the male. Females seek out tarantula burrows, paralyze them, and bury it in a burrow, laying a single egg. Larvae feed on the paralyzed spider.

Remarks

Genera Pepsis and Hemipepsis have similar biology and can be very difficult to distinguish in the field (but see "See Also" below). They are discussed here together under Pepsis, though there is a brief account for Hemipepsis.

These wasps are reputed to have a very powerful sting, though they are not aggressive.

Hemipepsis are often identifiable from photographs to species, but Pepsis are more difficult. Although it is often possible to narrow down the choices to groups of similar species, it is often impossible to assign a species name with certainty. An extensive knowledge of local fauna helps, as well as extensive work with museum specimens. Despite the large size of members of this genus many photographs will likely remain unidentified, as some of the species are very similar.

See Also

The related Spider Wasp genera, Hemipepsis and Entypus, are also quite large and can look very similar to Pepsis. These three genera are best distinguished by details of wing venation. For details, see the posts thumbnailed below:

Print References

Cazier, M. A. & M. Mortenson (1964). Bionomical observations on tarantula hawks and their prey (Hymenoptera Pompilidae): Pepsis. Ann. Ent. Soc. Amer. 57:533-541

Evans, H. E. 1953. Comparative ethology and the systematics of spider wasps. Syst. Zool. 2:155-172.

Hurd, Paul D. (1948). Systematics of the California species of the genus Pepsis Fabricius (Hymenoptera; Pompilidae). Univ. California Publ. Ent., vol. 8, pp. 123-150, 4 figs.

Passmore, L. (1936). Tarantula and tarantula hawk. Nature Magazine, 27:155-159.

Petrunkevitch, A. (1926). Tarantula versus tarantula hawk: a study in instinct. J. Exp. Zool. 45:367-394.

Petrunkevitch, A. (1952). The spider and the wasp. Sci. Amer. 187:20-33.

Punzo, F. (1994). 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. Psyche Vol. 101: 229-241. (Full Text)

Punzo, F. (1994). The biology of the spider wasp, Pepsis thisbe (Hymenoptera Pompilidae) from Trans Pecos, Texas. II. Temporal Patterns of Activity and Hunting Behavior With Special Reference to the Effects of Experience. Psyche Vol. 101: 243-256. (Full Text)

Punzo, F. & Ludwig, L. (2005). Behavioral Responses of Pepsis thisbe (Hymenoptera: Pompilidae) to Chemosensory Cues associated with host spiders. Journal of Insect Behavior. 18 (6): 757–766.

Swan, Lester A. & Papp, Charles S. 1972. The Common Insects of North America. Harper & Row, pp. 330, 546 — Description, illustrations of P. mildei & P. formosa(5)

Williams, F. X. (1956). Life history studies of Pepsis and Hemipepsis wasps in California (Hymenoptera: Pompilidae). Ann. Ent. Soc. Amer. 49:447-466.

Internet References

Fact sheet from DesertUSA website.

Works Cited