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Species Isodontia mexicana - Mexican Grass-carrying Wasp

What wasp please? - Isodontia mexicana Thread-waist - Isodontia mexicana Wasp Isodontia? - Isodontia mexicana Unknown wasp  - Isodontia mexicana Wasp, ID needed. - Isodontia mexicana Isodontia mexicana? - Isodontia mexicana wasp - Isodontia mexicana grass carrying wasp – Isodontia mexicana? - Isodontia mexicana - female
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon (Aculeata - Ants, Bees and Stinging Wasps)
No Taxon (Apoidea sans Anthophila – Apoid Wasps)
Family Sphecidae (Thread-waisted Wasps)
Subfamily Sphecinae
Tribe Sphecini
Genus Isodontia (Grass-carrying Wasps)
Species mexicana (Mexican Grass-carrying Wasp)
Female: 17mm. Male: 16 mm.
Body with pale instead of black hair (unlike philadelphica). Legs black (with reddish in auripes, exornata and elegans).
Very similar to apicalis. The characters used in identification keys (3 vs. 2 mandibular teeth) are almost never visible on images. The two species can be differentiated by the following subtle characters (for experienced users - added by Matthias Buck):

Males (7 visible abdominal segments, 11 flagellomeres):
- Abdomen ventrally with pale hair brushes (sparse hairing in apicalis)
- Posterior terga of abdomen with significant silvery reflections (under certain lighting) due to appressed pale hair (less so in apicalis)
- Posterior terga of abdomen with scattered short erect pale hair (absent in apicalis)
- First flagellomere long and slender (shorter in apicalis)
Male, showing abdominal hairing

Females (6 visible abdominal segments, 10 flagellomeres):
- Head short behind eyes (long in apicalis, 'block head')
- Ocellar triangle separated from hind margin of head by about 1-1.5x its width (2x in apicalis)
- Females from southern and western locations (e.g., Texas) often have wings tinted yellowish (dark brown in apicalis throughout its range)
Females, mexicana on left, apicalis is on right, difference in head shape
Mexicana females with yellow-tinged wings

Both sexes:
- Base of tergum 1 next to petiole often with a small brown spot (uniformly black in apicalis) - this character requires further testing but seems very reliable
Showing brown spot at base of tergum 1
May-October (North Carolina)
See Also
Print References
Brimley, p. 444 (1), lists (as Chlorion harrisi, apparently, see Calif. Academy Sciences) for Piedmont and mountains of North Carolina, May-October
Internet References
I. mexicana fact sheet. Penn State U.
Works Cited
1.Insects of North Carolina
C.S. Brimley. 1938. North Carolina Department of Agriculture.