Megarhyssa nortoni (Cresson, 1864)

Pook, Victoria G., Sharkey, Michael J. & Wahl, David B., 2016, Key to the species of Megarhyssa (Hymenoptera, Ichneumonidae, Rhyssinae) in America, north of Mexico, Deutsche Entomologische Zeitschrift 63 (1), pp. 137-148 : 143-145

Taxon classification Animalia Hymenoptera Ichneumonidae

Megarhyssa nortoni (Cresson, 1864) Figs 7, 8

Megarhyssa nortoni There are two subspecies:

Megarhyssa nortoni nortoni (Cresson).

Rhyssa nortoni Cresson, 1864. Ent. Soc. Phila., Proc. 3: 317.

Megarhyssa nortonii Dalla Torre, 1901. Cat. Hym., v. 3, p. 481. Emendation.

Megarhyssa nortoni quebecensis (Provancher).

Thalessa quebecensis Provancher, 1873. Nat. Canad. 5: 447.

Geographic range.

Megarhyssa nortoni nortoni is distributed along the Pacific Coast from south-western Canada to California, and extends eastward to central Colorado. Megarhyssa nortoni quebecensis is found in the north-eastern U.S. and adjacent parts of Canada. In the late 1960s and early 1970s this species was collected across the United States and Canada, encompassing the ranges of both subspecies, for introduction as a biocontrol agent in Australia ( Taylor 1976) and New Zealand ( Bartlett et al. 1978). The populations established in Australia were then introduced to South Africa ( Tribe and Cillié 2004).

Hosts.

Sirex noctilio ( Carlson 1979; Nuttall 1980; Valentine and Walker 1991; Vincent and King 1995); Sirex sp. ( Carlson 1979); Urocerus albicornis ( Champlain 1921; Townes 1944); Xeris morrisoni ( Townes 1944).

Diagnosis.

Female. Head black to blackish brown and yellow; mesosoma black or blackish brown, with yellow spots; metasoma brown and usually a little paler than me sosoma. Subtriangular median subapical spot on first and second tergites, large round yellow spot on side of tergites 3-5, and vertical yellow blotch on side of sixth and seventh tergites. Fore wing 13 to 29 mm long. Ovipositor sheath about 2.7 times as long as fore wing.

Females can be distinguished from Megarhyssa atrata by the body color; and from Megarhyssa macrurus and Megarhyssa greenei by the yellow spots on the tergites.

It should be noted that Carlson (1979) did not separate Megarhyssa nortoni nortoni from Megarhyssa nortoni quebecensis.

Male. Head black to blackish brown and yellow; mesosoma black to blackish brown, with yellow spots; metasoma brown, the tergites usually darker medially; the first two tergites with a median subapical yellow spot. Fore wing 9.5 to 20 mm long.

Males can be distinguished from Megarhyssa macrurus by the lack of a brown patch at the base of cell 2R1 of the fore wing and from Megarhyssa atrata and Megarhyssa greenei by the single vertical black band on the face and the color of the mesopleuron.