1a-d: Omphale faces (left), female antenna (center), and male antenna (right)
2a-c: Omphale male genitalia: O. straminea Hansson (left), O. longiseta Hansson (center), and O. aureopurpurea Hansson (right)
3a-b: Omphale flagellomeres with peg sensilla [sa]: slightly asymmetrical (left), and strongly asymmetrical (right)
Omphale obscurinotata species group:
Clypeus poorly set off from rest of face, not clearly delimited by sutures or distinct color (except for O. exserta Hansson, in which the clypeus is strongly protruding); apical margin convex. Antenna with slightly asymmetrical peg sensilla. Forewing with radial cell bare in all but O. masneri Hansson; no setal tracks radiating from stigmal vein; speculum closed posteriorly. Male genitalia with volsellar setae slightly flattened, arising far anteriad of usual position. Slide mounting necessary to distinguish this species group reliably from many genera. Compare with: Closterocerus (especially).
4a-b: Omphale obscurinotata face (left), and O. acuminativentris (Girault) male genitalia (right)
Biology: Parastioids of cecidomyiids.
Comments: Very large and diverse genus, likely paraphyletic. Can be the easiest or the most frustrating genus to identify, depending on the state of the clypeus. No other genus of Nearctic Entedoninae has species with a strongly broadened or protruding clypeus, but several have a "distinct," but more "normally-shaped" clypeus. Most keys are misleading on this point, making Omphale one of the most difficult genera of Entedoninae to consistently identify accurately. Even when all the facts are known, some species are very difficult to place to genus, requiring slide-mounting of males for confident exclusion of Omphale. This genus forms the major part of a clade including Perditorulus, Closterocerus, and Chrysonotomyia.
Perditorulus: Body unusually small (<1mm). Mandibles never exodont. Flagellar formula 2,4,1; heads of flagellar peg sensilla always elongate, strongly asymmetrical; pedicel about 3x longer than broad. Mesosomal dorsum with relatively long setae (also on vertex); midlobe of mesoscutum with 2 pairs of long setae. Forewing relatively narrow, with broad fuscate band posterior to marginal vein; postmarginal vein 0.3-0.7x stigmal vein length; no setal tracks radiating from stigma; speculum small, always closed posteriorly. Male genitalia without volsellar setae, but sometimes with paired "parameral" setae in which one pair is indistinguishable from volsellar setae; parameres often elongate or sinuate (especially helpful in species with ambiguously placed "parameral" setae). Color always dark with weak metallic tinge. Extremely difficult to distinguish with strong certainty. The only 100% reliable character is that of the male genitalia, which requires slide-mounting, and even that character is difficult to assess in some cases.
Closterocerus: Clypeus sometimes faintly defined by sutures, but always small and nearly square in shape. Some species with straight transverse frontal groove placed near median ocellus. Volsellar setae not enlarged. Face without cross-ridge between toruli and clypeus. May require slide-mounting to distinguish with certainty.
Ametallon: Mesoscutal midlobe with 1 pair of setae (the posterior pair) and forewing with 2 setal tracks radiating from the stigma. Volsellar setae not enlarged. Base of gaster with lateral indented, distinctly sculpted areas.
Chrysonotomyia: Transverse frontal groove straight, not v-shaped. Mesoscutal midlobe with 1 pair of setae (the posterior pair) and forewing with 2 setal tracks radiating from the stigma. Volsellar setae not enlarged. Some Omphale have only 1 pair of mesoscutal setae as well, but they can be distinguished by the v-shaped transverse frontal groove and the number of setal tracks radiating from the stigma. Chrysonotomyia always have 3 claval segments.
Chrysocharis sensu strictu: Volsellar setae not enlarged. Interscrobal ridge not meeting transverse groove. Petiole often as long or longer than broad, with dorsal sculpture (never in Omphale). Propodeum in many species with anterior median structures (often a triangle or anchor) formed by carinae, or with a pair of pits, a few species with plicae. Male flagellum never with whorls of erect setae. Flagellar peg sensilla always rounded, symmetrical. This genus is only rarely confusable with Omphale, but there are some Mexican species of Omphale with the interscrobal ridge not reaching the transverse frontal groove that could be misplaced here (see Hansson 1997).
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Hansson, C. 1996a. Taxonomic revision of the Nearctic species of Omphale Haliday (Hymenoptera: Eulophidae). Entomologica Scandinavica supplement 49.
Hansson, C. 1996b. A new genus of Eulophidae (Hymenoptera: Chalcidoidea) with remarkable male genitalia. Systematic Entomology. 21: 39-62.
Hansson, C. 1997. Mexican species of the genus Omphale Haliday (Hymenoptera: Eulophidae), a taxonomic study. Journal of Hymenoptera Research. 6(1): 107-151.
Image credits: Hansson (1996a).