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Subfamily Rhyssinae

giant ichneumon wasp - Megarhyssa macrurus - male early afternoon - Megarhyssa macrurus - female Big, Huge, Orange Wasp - Megarhyssa macrurus 02may2012-hym1 - Megarhyssa macrurus - female Megarhyssa greenei - female Giant Ichneumon - Megarhyssa macrurus - female Ichneumon wasp? - Rhyssella nitida - female Giant Ichneumon - Megarhyssa macrurus - female
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon ("Parasitica" - Parasitoid Wasps)
Superfamily Ichneumonoidea (Braconid and Ichneumonid Wasps)
Family Ichneumonidae (Ichneumonid Wasps)
Subfamily Rhyssinae
Numbers
15 spp.** in 4 genera* in our area; 234 described species in 8 genera worldwide (4 Oriental)(1)(2)(3)
*Genus not yet in the guide: Epirhyssa (1 sp.)
**Species not yet in the guide: E. dietrichi (conspicuously yellow-marked: AZ)(4), Rhyssa hoferi (reddish with white abdominal bands: CO, NM, AZ)(5), Rhyssella perfulva (bright orange and yellow: FL)(6)
Size
Ovipositors may exceed 200 mm(3)
Identification
Medium to large size, very long ovipositor, cylindrical abdomen becoming dorsolaterally compressed apically, hind coxae length more than twice their width. In all but 1 species in our area (Epirhyssa dietrichi), there's a small triangular areolet.

Rhyssinae are distinguished from all other ichneumonids, apart from Pseudorhyssa nigricornis (Pimplinae: Delomeristini) by the strong ridges on the mesoscutum.

Pseudorhyssa can be ruled out by the presence of anterolateral grooves on T2 of the abdomen not found in Rhyssinae and/or having the apex of T8 not terminating as a polished horn as in Rhyssinae.(7)

Some Pimplinae (esp. Ephialtini) are also superficially similar. Pimplinae can be ruled out as they lack the extent of transverse ridges on the mesoscutum found in Rhyssinae. Some Pimplinae also have more of a quadrate areolet, when present.

Range
Worldwide except Australian(1); in the New World, the highest diversity occurs in the ne. hardwood forests, whilst in tropical countries there are only 2 genera(3)
Food
Idiobiont ectoparasitoids of the immature wood-boring endopterygote insects, in our area usually larval woodwasps (Siricidae and Xiphydriidae), but may also develop as facultative hyperparasitoids using other woodwasp parasitoids as hosts or on virtually any endopterygote (some have even been cultured in the laboratory on entirely unnatural surrogate hosts)(3)
Works Cited
1.Classification and Systematics of the Ichneumonidae
2.Carlson R.W. () Ichneumonidae catalog
3.Genera Ichneumonorum Nearcticae (2014)
4.Ichneumon-Flies of America North of Mexico: 2. Subfamilies Ephialtinae, Xoridinae, and Acaenitinae
Henry Townes and Marjorie Townes. 1960. Bulletin - United States National Museum, Vol. 216, Part 2, pp. 1–676.
5.The North American Ichneumon-flies of the Tribes Labenini, Rhyssini, Xoridini, Odontomerini, and Phytodietini
S.A. Rohwer. 1920. Proceedings of the United States National Museum 57: 405-474.
6.New species and records of Rhyssa and Rhyssella (Hymenoptera: Ichneumonidae: Rhyssinae) from Florida and Central America
Charles C. Porter. 2001. Insecta Mundi, Vol. 15, No.3.
7.Detection and identification of two new native hymenopteran parasitoids associated with the exotic Sirex noctilio
Christopher R. Standley, E. Richard Hoebeke, Dylan Parry, Douglas C. Allen, & Melissa Kay Fierke. 2012. Proceedings- Entomological Society of Washington 114(2):238-249.