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Perilissus Holmgren, 1856: 63. Type species: Ichneumon filicornis Gravenhorst, 1820. Monobasic.

Spanotecnus Foerster (1869): 197. Type species: Ichneumon filicornis Gravenhorst, 1820. Based on subsequent designation by Viereck (1914), chosen from among the four species that were first included in Spanotecnus by Thomson (1883). Synonymy indicated by Dalla Torre (1901).

Ichnaeops Foerster (1869): 197. Type species: Perilissus lutescens Holmgren, 1857. Designated by Perkins (1962). Synonymized independently and almost simultaneously by Townes et al. (1961) and Perkins (1962).

Polyoncus Foerster (1869): 197. Type species: Tryphon erythrocephalus Gravenhorst, 1829. Based on subsequent designation by Viereck (1914), chosen from among the three species that were first included in Polyoncus by Thomson (1883). Synonymized by Townes (1945).

Udenia Foerster (1869): 202. Type species: Perilissus (Udenia) herrichii Kriechbaumer, 1892. Based on subsequent inclusion by Kriechbaumer (1892). Monobasic. Synonymized by Schmiedeknecht (1912).

Exacrodus Foerster (1869): 210. Type species: Exacrodus populans Morley, 1913. Based on subsequent inclusion by Morley (1913). Monobasic. Synonymized independently and almost simultaneously by Townes et al. (1961) and Perkins (1962).

Daugna Seyrig, 1935: 29. Type species: Daugna alluaudi Seyrig, 1935. Original designation. Synonymized by Townes et al. (1965).

Pseudochorus Rao, 1953: 195. Type species: Pseudochorus kuriani Rao, 1953. Original designation. Synonymized by Townes et al. (1961).

There are approximately 65 valid species in Perilissus (Yu and Horstmann 1997, Aubert 2000, Yu et al. 2005). Based on the current classification, Perilissus and Lathrolestes are easily the largest genera in Perilissini, with only a few more species of Lathrolestes than Perilissus as of 2011.

Holmgren’s original publication (Holmgren 1856) is often cited as 1855 (e. g. Townes 1970). Carlson (1979) gives the actual data of publication as 1856. Yu and Horstmann (1997) and Yu et al. (2005) give a publication date of 1855 under Perilissus, but erroneously attribute authorship to Foerster. They do, however, give 1856 as the actual date of publication for Holmgren’s first publication on Perilissus. Holmgren (1856, 1857) described Perilissus in two separate publications, the first containing but a single species and the second in which he included several species. Viereck (1912), perhaps unaware of this, specifically designated Mesoleptus limitaris Gravenhorst as the type species of Perilissus, stating that several species were originally included in Perilissus by Holmgren (1857). Townes (1945), however, without mentioning Viereck’s designation, gives the type species as “Mesoleptus filicornis Gravenhorst. Monobasic.” Despite the confusion in dates, authorship, and designations, filicornis has been recognized as the type species in all subsequent publications.

Perilissus Holmgren, 1856 and Spanotecnus Foerster, 1869 have the same type species and Spanotecnus must therefore be treated as a junior objective synonym of Perilissus. Gupta (1987) suggests that this synonymy should be attributed to Dalla Torre (1901). Dalla Torre (1901) treated both as valid genera, but listed Perilissus sensu Holmgren and recent authors as one of the synonyms under Spanotecnus.

Members of the genus Perilissus are recognized on the basis of the distinctive glymma (Figs 1, 2) in combination with the lack of all the other specific features used to identify other members of the Perilissini, as exemplified by the key in Townes (1970).

In one of the first revisions of Nearctic species, Burks (1952) differentiated Perilissus from Lathrolestes and two other perilissine genera on the basis of the separation of the occipital and hypostomal carinae ventrally, with the two carinae not joined before reaching the base of the mandible in Lathrolestes. Townes (1970) also used this character for segregating Lathrolestes from most other perilissine genera and Barron (1992, 1994) largely followed Burks and Townes, but noted exceptions for a few species. Gauld (1997), however, in his revision of Costa Rican ctenopelmatines, separated Lathrolestes from Perilissus on the basis of the shape and sculpture of the first metasomal tergite (T1), and stated that the arrangement of the hypostomal and occipital carinae was the same in the two genera. This represents a major change in concept for the two genera, and would likely necessitate the transfer of several species if the Holarctic Perilissus and Lathrolestes were to be separated in this fashion. The shape and sculpture of T1 is rather homoplastic among perilissines, however, and does not seem to offer an improved method for segregating the species of these genera. Nevertheless, both genera are large and unwieldy, containing heterogeneous assemblages of species. Neither genus is demonstrably monophyletic and it will likely be necessary break these into small groups to achieve a more satisfactory classification. In this regard, Barron (1992) provides some characters useful for recognizing species groups and these should facilitate the delimitation of smaller, monophyletic units.

Clypeus with ventral margin bluntly rounded, usually thickened, especially medially; ventral margin usually convex, sometimes strongly so, rarely truncate; epistomal sulcus often absent or nearly so, sometimes weakly indicated, more rarely distinct; clypeus weakly to strongly protruding in profile. Malar space distinct, often at least half basal width of mandible. Mandible usually with ventral tooth much longer than dorsal tooth, less commonly only slightly longer. Ocelli in most species small, lateral ocellus distinctly shorter than distance between ocellus and eye, more rarely in some pale-colored species with lateral ocellus a little longer than distance between ocellus and eye. Maxillary palp usually about equal to head height, less commonly shorter, rarely longer; female antennae about as long as body or longer; first flagellomere with discrete tyloid containing fewer than 15 sensilla (Fig. 2). Hypostomal carina usually joining occipital carina well above base of mandible, more rarely the two carinae meeting at or near base of mandible; occipital carina complete. Dorsal end of epicnemial carina distant from margin. Notaulus usually varying from absent to broadly and very shallowly impressed near base; more distinct in two of the species examined: distinctly and narrowly impressed basally and extending posteriorly at least to level of tegula as a shallow groove. Well-developed u-shaped groove or notch present between propodeum and metanotum in lateral view in most species, more rarely weakly developed or nearly v-shaped; pleural carina complete, nearly always well-developed throughout, occasionally weaker posteriorly; propodeal carinae well-developed in some species (Fig. 3), including presence of a complete, usually hexagonal areola, but in other species the propodeal carinae are reduced anteriorly, often largely effaced anteriorad posterior transverse carina and rarely with only the posterior transverse carina present. Apical margin of mid tibia often expanded to form a tooth similar to that of the fore leg; apical comb on posterior face of hind tibia usually well developed; posterior hind tibial spur at least 7x longer than maximum width at base; tarsal claws varying from completely pectinate to pectinate only basally (without pectination over apical half). Fore wing areolet nearly always present; stigma broad to very broad, never narrowly elongate, Rs+2r arising at or near midpoint. Hind wing with first abscissa of CU1 often distinctly shorter than 1cu-a, sometimes only slightly shorter that 1cu-a, and rarely longer than 1cu-a. T1 (Figs 3-5) usually long and slender, without dorsal carinae; without distinct basal depression at dorsal tendon attachment, but dorsal surface occasionally strongly angled towards base anteriorly; dorsal-lateral carina extending from spiracle to apex of T1 in most species, absent in some; glymmae (Fig. 5) on each side meeting on the midline posterior to dorsal tendon attachment, deep, separated at midline by translucent partition. T2 thyridium absent in about two-thirds of species examined, present and distinct in others; laterotergites of T2 and T3 completely separated by creases. Ovipositor usually straight (Figs 6-8), sometimes upcurved (Fig. 8), subapical notch widely varying from very deep (Figs 6, 7) to very shallow, barely indicated (Figs 8, 9), when deep the notch may be either broad or narrow; ovipositor sheath narrow, parallel-sided, broadly rounded to nearly pointed apically. Male parameres (Figs. 10, 11) varying from relatively short and broadly rectangular distally in dorsal view to very narrowly attenuate and in one species with more or less parallel-sided, flap-like distal extensions; aedeagus rounded and clubbed distally.

Perilissus is mostly Holarctic but with some species also described from the Neotropical, Oriental, and Ethiopian regions.

This page was assembled by Bob Wharton as part of a larger collaborative effort on the genera of Ctenopelmatinae.

This work would not have been possible without the groundwork provided by Ian Gauld’s study of the Australian and Costa Rican faunas, and we are particularly grateful for his assistance in many aspects of this study. We also thank Gavin Broad for extended loans of the material used for this study and exchange of information on Perilissini as well as David Wahl of the American Entomological Institute and Andy Bennett of the Canadian National Collection. We also thank David Wahl for assistance in locating Holmgren (1856) and for useful feedback throughout our study. Matt Yoder provided considerable assistance with databasing issues, and our use of PURLs (http://purl.oclc.org) in this regard follows the example of their use in publications by Norm Johnson. Heather Cummins, Andrea Walker, Patricia Mullins, Caitlin Nessner, Amanda Ladigo, and Cheryl Hyde graciously assisted with image processing, formatting, and literature retrieval. This study was supported by the National Science Foundation’s PEET program under Grant No. DEB 0328922 and associated REU supplement nos DEB 0723663, 0923134, and 1026618. Page last updated January, 2015.

This material is based upon work supported by the National Science Foundation under Grant Number DEB 0328922 with REU supplements DEB 0723663, 0923134, and 1026618. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.