Contribution to the taxonomy of Mexican Tersilochinae (Hymenoptera, Ichneumonidae), with descriptions of five new species

Abstract Five new species of Tersilochinae (Ichneumonidae) are described from Mexico: Meggoleus hidalgoensissp. nov., M. whartoni Khalaim, sp. nov., Phradis belovi Khalaim, sp. nov., Stethantyx covidasp. nov., and St. oaxacanasp. nov.Meggoleus whartoni Khalaim, sp. nov. is also recorded from Panama, and St. covidasp. nov. from Guatemala. The species recently described from Mexico Probles contrerasi Khalaim & Ruíz-Cancino is transferred to the genus Gelanes Horstmann, comb. nov. A partial key to the species of Meggoleus with small propodeal spiracles and a key to Mexican species of Phradis are provided.


Introduction
The Tersilochinae is a moderately large, cosmopolitan subfamily of parasitoid wasps comprising more than 560 described species in 27 genera (Yu et al. 2016;Khalaim pers. obs.). The primary hosts of tersilochine parasitoids are larvae of various Coleoptera, but lepidopteran (Lepidoptera: Eriocraniidae) and symphytan (Hymenoptera: Tenthredinidae, Xyelidae) larvae also serve as hosts of some tersilochine taxa (Yu et al. 2016).
The aim of this work is to describe five new species in the genera Meggoleus, Phradis, and Stethantyx from Mexico, revise the generic positions of recently described species of Probles, and provide identification keys to the species of Meggoleus and Phradis.

Materials and methods
A large number of tersilochine specimens was examined from the Universidad Autónoma de Tamaulipas, Cd. Victoria, Mexico (UAT); Instituto de Biología, Universidad Nacional Autónoma de México, D.F., Mexico (UNAM); and Texas A&M University, College Station, Texas, USA (TAMU). Additional paratype of Stethantyx covida sp. nov. was loaned from the University of California, Riverside, California, USA (UCR), and several paratypes are preserved in the Natural History Museum, London, UK (BMNH), Florida State Collection of Arthropods, Gainesville, Florida, USA (FSCA) and Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia (ZISP).
Morphological terminology follows that of Townes (1969) with changes according to Khalaim (2011). Photographs were taken in the Zoological Institute RAS (St. Petersburg, Russia), with a Canon EOS 70D digital camera attached to an Olympus SZX10 stereomicroscope. Images were assembled with Helicon Focus 6 Pro software. General data on the distribution and biology of the genera follow the catalogue Taxa-Pad (Yu et al. 2016).
It is a small Neotropical genus with five species; one Afrotropical species with large propodeal spiracles described in the genus Meggoleus (Khalaim 2007) was recently found to belong to the genus Allophrys Förster (Khalaim 2017). Nothing is known about host range of any Meggoleus species.
Three species of Meggoleus occurring in South America were revised by Alvarado (2012). Two of them, M. spirator Townes and M. pampahermosensis Alvarado, are known from Costa Rica Broad 2012, Khalaim et al. 2018), and the latter species was recorded also from Mexico . In this paper, we describe two new species of Meggoleus from Mexico and Panama. Both new species possess small propodeal spiracles, clearly differing from three previously known taxa which are characterized by strongly enlarged propodeal spiracles. Record of M. hidalgoensis sp. nov. from Tamaulipas is a northernmost known locality for the genus Meggoleus. A partial key to the species of Meggoleus with small propodeal spiracles is provided.
Key to species of Meggoleus (partial)  (Fig. 4), weakly convex in lateral view, separated from face by sharp furrow; smooth, with scattered punctures in upper part, sometimes slightly scabrous near upper and lower margins. Mandible not constricted, with upper and lower margins mostly subparallel, distinctly widened at level of teeth; teeth somewhat divergent, upper tooth ca. 1.5 × longer than the lower. Malar space 0.9-1.2 × as long as basal mandibular width. Antennal flagellum (Fig. 3) with 15 or 16 flagellomeres, basally very slender; basal flagellomeres more than 2.5 × as long as broad, subapical flagellomeres distinctly elongate; flagellomeres 4-7 bearing long and thin subapical finger-shaped structures on outer surface (hardly discernible in light microscope). Face weakly convex. Face, frons, and vertex subpolished, weakly shining, with very fine, mostly indistinct punctures. Gena polished, with fine and sparse punctures. Occipital carina complete, somewhat dipped mediodorsally, evenly arcuate in dorsal view. Hypostomal carina absent at least in lower part.
Fore wing with second recurrent vein (2m-cu) postfurcal, weakly pigmented in anterior part and distinct posteriorly. First abscissa of radius (Rs+2r) straight, somewhat longer than width of pterostigma. First and second abscissae of radius (Rs+2r and Rs) meeting at slightly acute angle. Intercubitus (2rs-m) slightly thickened, approximately as long as abscissa of cubitus between intercubitus and second recurrent vein (abscissa of M between 2rs-m and 2m-cu). Metacarpus (R1) almost reaching apex of fore wing. Second abscissa of postnervulus (Cu&2cu-a) present, thus brachial cell is closed posteriorly. Hind wing with nervellus (cu1&cu-a) weakly reclivous. Legs slender. Tarsal claws long and slender, not pectinate.
First tergite ca. 3.8 × as long as posteriorly broad, smooth, sometimes with very weak striae laterally just before glymma; petiole more or less trapeziform in cross-section centrally; in dorsal view, postpetiole distinctly widened at base, wider than petiole and clearly separated from it (Fig. 7); in lateral view, upper margin of tergite weakly arcuate in basal 0.6 and somewhat stronger arcuate in apical 0.4 (Fig. 6). Glymma distinct, situated in apical 0.6 of tergite, joining by weak groove with lower part of postpetiole ( Fig. 6), but sometimes this groove is vestigial and glymma is virtually isolated. Second tergite ca. 1.85 × as long as anteriorly broad (Fig. 7). Thyridial depression shallow to deep, 2.0-3.0 × as long as broad, with posterior end rounded. Ovipositor weakly and nearly evenly bent upwards over its total length, with weak dorsal subapical depression (Fig. 8); sheath 1.0-1.4 × as long as first tergite (1.4 × in holotype).
Head and mesosoma black. Palpi, mandible (teeth dark red), lower 0.4-0.5 of clypeus and tegula brownish yellow. Scape and pedicel of antenna yellow-brown ventrally and brown dorsally; flagellum brownish black, sometimes pale at base. Pterostigma brown. Legs brownish yellow; hind coxa darkened with brown at base; apex of hind tibia and hind tarsus infuscate. First tergite brown to dark brown. Metasoma posterior to first tergite brown or dark brown dorsally to brownish yellow ventrally.
Variation. Pale specimens have head and mesosoma mostly reddish brown rather than black, and metasoma pale brown to yellow. Two females from the State of Oaxaca possess foveate groove of mesopleuron very thin, represented by a line of sharp and deep pits.
Etymology. The species is named after the type locality, [State of ] Hidalgo. hidalgoensis sp. nov. as both have small propodeal spiracles but differs from this species, in addition to color pattern of the flagellum, by scutellum with shorter lateral longitudinal carinae and fore wing with short and thick intercubitus (2rs-m). Description. Female. Body length 3.7 mm. Fore wing length 2.8 mm.
Head, in dorsal view, strongly constricted, weakly rounded posterior to eyes; gena 0.6-0.65 × as long as eye width. Eyes glabrous. Clypeus relatively large, almost lenticular (slightly truncated ventrally), ca. 2.5 × as broad as long (Fig. 11), very weakly convex in lateral view, separated from face by fine furrow; smooth, with very fine punctures in upper 0.3-0.5. Mandible slender, not constricted, with upper and lower margins mostly subparallel; upper tooth almost twice longer than the lower. Malar space approximately as long as basal mandibular width. Antennal flagellum ( Fig. 10) with 15 flagellomeres, basally very slender; basal flagellomeres almost 2.5 × as long as broad, subapical flagellomeres distinctly elongate; flagellomeres 4 to 6 bearing long and thin subapical finger-shaped structures on outer surface. Face weakly convex. Face and frons subpolished, weakly shining, with very fine punctures. Vertex polished, with very fine and sparse punctures. Gena polished, impunctate. Occipital carina complete, somewhat dipped mediodorsally, evenly arcuate in dorsal view. Hypostomal carina present in upper part, weak or completely obliterated in lower part.
Fore wing with second recurrent vein (2m-cu) postfurcal, weakly pigmented in anterior part and distinct posteriorly. First abscissa of radius (Rs+2r) straight, longer than width of pterostigma. First and second abscissae of radius (Rs+2r and Rs) meeting at slightly acute angle. Intercubitus (2rs-m) short and very thick, much shorter (0.5 × or less) than abscissa of cubitus between intercubitus and second recurrent vein (abscissa of M between 2rs-m and 2m-cu). Metacarpus (R1) almost reaching apex of fore wing. Second abscissa of postnervulus (Cu&2cu-a) present, thus brachial cell is closed posteriorly. Hind wing with nervellus (cu1&cu-a) weakly reclivous. Legs slender. Tarsal claws long and slender, not pectinate.
First tergite ca. 4.4 × as long as posteriorly broad, predominantly smooth, with weak striae laterally before glymma; petiole trapeziform in cross-section centrally; in dorsal view, postpetiole widened at base, distinctly broader than petiole and clearly separated from it; in lateral view, upper margin of tergite weakly arcuate in basal 0.6 and somewhat stronger arcuate in apical 0.4. Glymma distinct, situated in apical 0.6 of tergite, joining by weak (sometimes vestigial) groove with lower part of postpetiole (Fig. 12). Second tergite approximately twice as long as anteriorly broad. Thyridial depression deep, ca. 2.5 × as long as broad, with posterior end rounded. Ovipositor weakly and nearly evenly bent upwards over its total length, with weak dorsal subapical depression; sheath approximately as long as first tergite.
Head, mesosoma and first tergite of metasoma orange-brown to dark reddish brown. Palpi and mandible (teeth red) yellow. Clypeus yellow-brown or reddish brown, unicolorous or slightly darkened in upper part. Tegula brownish yellow. Scape and pedicel of antenna yellow-brown ventrally and brown dorsally; flagellum brownish black with two or three distal flagellomeres white (Fig. 10) A moderately large predominantly Holarctic genus with 20 species in the Nearctic region (including two species from Mexico), ca. 40 species in the Palaearctic region, and several species known from Peru, South Africa, and Australia. In Europe, species of Phradis have been reared from sap beetle larvae (Coleoptera: Nitidulidae: Meligethes spp.) feeding on rape, but no host record is known for any Nearctic species (Horstmann 2013a).
Two species of Phradis were known from Mexico until now (Khalaim and Ruíz-Cancino 2018), and the third species, P. belovi sp. nov., is described from North Mexico in this paper. The genus is extremely rare in Mexico as all known Mexican species are represented by a single holotype. Horstmann (2013a) in his revision of the Nearctic fauna, also noted that many Nearctic species are rarely collected, and six of 18 revised species (33%) are known from only one specimen. A key to three Mexican species of Phradis is provided below.
Key to species of Phradis occurring in Mexico

1
Flagellum with 17 flagellomeres (Fig. 16). Fore wing with vein 2m-cu postfurcal. Notaulus very shallow, with short wrinkle or tubercle distant from anterolateral margin of mesoscutum. Propodeum mediodorsally with narrow longitudinal furrow, without delimited basal area; dorsolateral areas polished. Hind femur brownish yellow, not darkened (Fig. 15) Differential diagnosis. Phradis belovi sp. nov. may easily be recognized by the postfurcal second recurrent vein (2m-cu) in the fore wing, narrow and sharp foveate groove on the mesopleuron (Fig. 19), and propodeum with longitudinal furrow mediodorsally and polished dorsolateral areas. It differs from two other Mexican species of Phradis by features given in the key above. In the key to Nearctic species of Phradis (Horstmann 2013a: 68), P. belovi sp. nov. runs to P. nitidipleuris Horstmann in couplet 17, but differs from this species by the propodeum mediodorsally with longitudinal furrow (short and broad, irregularly wrinkled basal area in P. nitidipleuris, see fig. 77 in Horstmann 2013a: 82), longer metacarpus in the fore wing ( Fig. 15 and Khalaim 2019: 413, fig. 52), and its narrow and sharp foveate groove on the mesopleuron (Fig. 19) (broad, with irregular wrinkles in P. nitidipleuris, see Khalaim 2019: 413, fig. 5). Description. Female. Body length 4.3 mm. Fore wing length 3.3 mm. Head, in dorsal view, rounded posterior to eyes (Fig. 18); gena 0.65 × as long as eye width. Eyes glabrous. Clypeus relatively large, lenticular, 2.6 × as broad as long (Fig. 17), weakly convex in lateral view, separated from face by thin and sharp furrow, with flattened area in lower part centrally; smooth, with fine punctures on slightly scabrous background in upper 0.4. Mandible robust, not constricted (i.e. with upper and lower margins subparallel in front view); upper tooth somewhat longer than the lower. Malar space approximately as long as basal mandibular width. Antennal flagellum filiform, with 17 flagellomeres (Fig. 16); flagellomeres 2 and 3 ca. 2.5 × as long as broad, subapical flagellomeres slightly elongate; flagellomeres 4-7 bearing long and thin subapical finger-shaped structures on outer surface (hardly discernible in light microscope). Face with slightly elongated convexity centrally. Face, frons, and vertex with very fine and dense punctures; gena impunctate anteriorly, with fine and sparse punctures in posterior half. Face and frons subpolished, weakly shining. Vertex and gena polished. Occipital carina complete, weakly and evenly arcuate in dorsal view (Fig. 18), somewhat flattened mediodorsally.
Mesoscutum very finely and densely punctate on very finely and shallowly granulate background, weakly shining, except for central lobe which is dull, with somewhat denser granulation and mostly without distinct punctures. Notaulus very shallow, with short wrinkle or tubercle distant from anterolateral margin of mesoscutum. Scutellum with lateral longitudinal carinae at basal 0.1. Epicnemial carina with upper end at level of centre of pronotum, not reaching front margin of mesopleuron (Fig. 19). Foveate groove situated in center of mesopleuron, very narrow and sharp, anteriorly upcurved (Fig. 19). Mesopleuron smooth and shining, finely punctate. Propodeal spiracle small, round, separated from pleural carina by 1.5 × diameter of spiracle. Propodeum with dorsal part convex in lateral view (Fig. 19), with narrow median longitudinal furrow which is ca. 0.7 × as long as apical area. Dorsolateral area polished, impunctate. Apical area flat, widely rounded anteriorly; apical longitudinal carinae almost reaching transverse carina anteriorly, indistinct next to transverse carina because of irregular wrinkles.
Fore wing with second recurrent vein (2m-cu) distinctly postfurcal, weakly pigmented in anterior 0.6. First abscissa of radius (Rs+2r) straight, distinctly longer than width of pterostigma. First and second abscissae of radius (Rs+2r and Rs) meeting at right angle. Intercubitus (2rs-m) slightly thickened, twice as long as abscissa of cubitus between intercubitus and second recurrent vein (abscissa of M between 2rs-m and 2mcu). Metacarpus (R1) reaching ca. 0.7 the distance from distal corner of radial cell to the tip of wing. Second abscissa of postnervulus (Cu&2cu-a) present but short, thus brachial cell is partly open posteriorly. Hind wing with nervellus (cu1&cu-a) straight, weakly reclivous. Legs slender. Tarsal claws slender, not pectinate.
First tergite ca. 4.1 × as long as posteriorly broad, smooth, without glymma but with sharp oblique groove (Fig. 19), with upper margin in lateral view straight in basal half and arcuate in apical half; petiole round in cross-section centrally. First tergite, in dorsal view, weakly and rather evenly widened from base towards apex, thus postpetiole is weakly separated from petiole. Second tergite 2.5 × as long as anteriorly broad. Thyridial depression distinct, ca. 2.5 × as long as broad, with posterior end somewhat pointed. Ovipositor weakly and evenly bent upwards over its total length, with weak dorsal subapical depression (Fig. 20); sheath twice as long as first tergite.
Head, mesosoma and first tergite of metasoma black; clypeus brown in lower 0.4 and dark brown in upper 0.4, with narrow transverse brownish yellow band. Palpi, mandible (teeth dark red) and tegula brownish yellow. Scape and pedicel of antenna yellow-brown, flagellum pale brown basally to black apically. Pterostigma brown. Legs brownish yellow; fore and mid coxae browish, hind coxa dark brown. Metasoma posterior to first tergite predominantly dark brown, tergites 2 and 3 laterally brown (Fig. 15).
Male. Unknown. Etymology. The species is named after my friend, the well-known entomologist Vassili Belov (TAMU).

Genus Stethantyx Townes, 1971
Type species. Stethantyx nearctica Townes, 1971. Large and almost exclusively Neotropical genus with ca. 50 described and many undescribed species. Three species of Stethantyx occur in America north of Mexico, including one species introduced from South America (Horstmann 2010), and six Mexican species were reviewed by Khalaim and Ruíz-Cancino (2013). Species of the genus are known as parasitoids of coleopteran hosts of the families Curculionidae and Nitidulidae.
Two new species of Stethantyx are described here from Mexico, raising the total number of known Stethantyx species in Mexico to eight. The both new species possess right-angled radial cell in the fore wing and belong to the species group radiata (see Khalaim et al. 2015), while other six Mexican species belong to the species group nearctica, as they have abscissae of radius (Rs+2r and Rs) meeting at obtuse angle (see Broad 2013, Khalaim et al. 2013).
Head, in dorsal view, roundly constricted posterior to eyes; gena 0.9-1.0 × as long as eye width. Eyes glabrous. Clypeus lenticular (sometimes with lower margin slightly truncate), 3.2-3.4 × as broad as long, weakly convex in lateral view, with weak transverse ridge in lower 0.3-0.4, separated from face by sharp furrow; smooth, with fine punctures in upper part. Mandible slender, distinctly constricted in basal 0.3-0.4; upper tooth 2.0-2.5 × as long as the lower. Malar space 0.9-1.1 × as long as basal mandibular width. Antennal flagellum (Fig. 22)  Mesoscutum and mesopleuron very finely (sometimes indistinctly) punctate on smooth background; dorsolateral area of propodeum polished, impunctate. Notaulus with strong wrinkle on anterolateral side of mesoscutum. Scutellum with lateral longitudinal carinae at basal 0.3-0.5. Epicnemial carina not reaching front margin of mesopleuron, continuing above along front margin of mesopleuron, and vanishing there (Fig. 23). Foveate groove situated in anterior half of mesopleuron, deep, strongly oblique, almost straight, with distinct transverse wrinkles (Fig. 23). Propodeal spiracle small, adjacent to pleural carina or separated from it by one diameter of spiracle (Fig. 23). Propodeum with long and narrow basal area (basal longitudinal carinae parallel or weakly divergent anteriorly) which is 0.5-0.8 × (0.6 in holotype) as long as apical area (Fig. 24). Apical area flat, rounded to slightly pointed anteriorly; apical longitudinal carinae complete and reaching transverse carina anteriorly.
First tergite 4.0 × as long as posteriorly broad, smooth, usually with longitudinal striae laterally before glymma and dorsally at apex of petiole; petiole slightly trapeziform in cross-section centrally; in dorsal view, postpetiole distinctly widened at base, wider than petiole and clearly separated from it; in lateral view, upper margin of tergite straight or weakly arcuate in basal 0.6-0.7 and arcuate in apical 0.3-0.4. Glymma  as broad, with posterior end usually rounded. Ovipositor bent upwards over its total length, with weak dorsal subapical depression and without teeth ventrally (Fig. 26); sheath 2.7-3.5 × (3.2 in holotype) as long as first tergite.
Head, mesosoma and first tergite brownish black to black; clypeus brownish yellow in lower 0.4 and dark brown in upper part, but sometimes clypeus is more or less entirely brownish yellow. Palpi and mandible (teeth red) brownish yellow. Tegula brownish yellow to brown. Antenna dark brown to black, scape and pedicel sometimes yellow-brown ventrally. Pterostigma brown. Legs brownish yellow; coxae and trochanters sometimes strongly darkened with brown (to almost black), tibiae and tarsi sometimes weakly to strongly infuscate (Fig. 21). Metasoma entirely or predominantly dark brown, sometimes brown posteriorly and ventrally.
Male. Similar to female but malar space somewhat shorter than basal mandibular width; basal area of propodeum very narrow and usually longer; and second metasomal tergite and thyridial depression longer.
Variation. Two females from Nevado de Toluca (State of Mexico) possess second tergite 1.5-1.6 × as long as anteriorly broad. Epicnemial carina sometimes almost reaching front margin of mesopleuron. Foveate groove in small specimens sometimes weak.
Etymology. This abundant Mexican species is named after the Covid-19 (Coronavirus) because the taxon was described while the outbreak of this virus in Mexico.
Material examined. Holotype female (UAT), Mexico, Tamaulipas Differential diagnosis. The new species is very similar to St. covida sp. nov. but differs from this species in the shape of the ovipositor (Fig. 32), and shorter gena and second tergite. Stethantyx oaxacana sp. nov. also resembles St. radiata Khalaim & Sääksjärvi as both have similar shape of the ovipositor apex, but distinct in having clypeus separated from face by sharp furrow, less punctate head and mesosoma, and longer ovipositor.
Mesoscutum and mesopleuron finely punctate on smooth background. Notaulus with strong wrinkle on anterolateral side of mesoscutum. Scutellum with lateral longitudinal carinae at basal 0.3-0.5. Epicnemial carina not reaching front margin of mesopleuron, continuing above along front margin of mesopleuron and vanishing there (Fig. 30). Foveate groove situated in anterior half of mesopleuron, deep, strongly oblique, almost straight, with distinct transverse wrinkles (Fig. 30)