Other Common Names
Bent-shielded besieger wasp
Synonyms and other taxonomic changes
Gnamptopelta obsidianator (Brulle, 1846)
Explanation of Names
Species name likely from Latin obsidere, meaning to watch over, to besiege, to be on the lookout for. (Latin Dictionary). Suffix -nator indicates "one who", so this is the "Bent-shielded (Gnamptopelta) besieger".
Very large blue-black Ichneumon with orange antennae. Abdomen crescent-shaped, flattened, and strongly bent downward. Frequents flowers, presumably seeking nectar (?). Several other ichneumonids have this same general pattern (Eric Eaton--comments under various photos). Eric Eaton was kind enough to ask the opinion of Bob Carlson of the USDA-SEL, who provided the identification--see photos in guide.
These large ichneumons resemble spider wasps (Pompilidae) with their beautiful blue-black coloration and prominent orange marks. They are likely mimics of such wasps as Entypus
and Pepsis menechma
All have orange antennae. Presumably the spider wasp has a wicked sting, but not the ichneumon.
Widespread eastern United States into Canada
Fields with flowers, also forests
Late spring-summer, into early fall in North Carolina. Brimley, p. 403, lists Trogus obsidinator
for May, June, Trogus austrinus
for May. (1)
Guide photos for North Carolina are later in the season.
Adults take nectar, apparently.
Parasitiod on Sphingid Lepidoptera larvae, especially those found on grapes, Vitis.
Note that identification of species in this family is exceptionally difficult, if not impossible, from photographs, except in a few cases. Note the comments under each photo listed under this species here.
-no local photo-
is a closely-allied species that is essentially identical in coloration. Genus-level differences include the structure of the petiole (with a conical elevation at the base in Conocalama
; absent in Gnamptopelta
) and structure of the scutellum (only slightly elevated in Conocalama
; distinctly conical in Gnamptopelta
males are similarly colored but differ in terms of the short, non-conical scutellum and smoother, non-beaded structure of the abdomen.
is a similarly-colored ophionine species that was frequently confused with Gnamptopelta obsidianator
in the early years of BugGuide. This species differs in subfamily-level traits including the distinct lateral compression of the abdomen not found in the ichneumonines. The abdomen also has a distinct "knob" at the end of the petiolus.
Brimley, p. 403, lists Trogus obsidinator, T. austrinus
for North Carolina. These are now apparently considered subspecies. (1)
Sime, K. R., and D. B. Wahl. 1998. Taxonomy, mature larva and observations on the biology of Gnamptopelta obsidianator (Brullé) (Hymenoptera: Ichneumonidae, Ichneumoninae). J. Hym. Res. 7(2): 157-164.