Revision of Nearctic Heterischnus Wesmael, 1859 (Hymenoptera, Ichneumonidae, Ichneumoninae, Phaeogenini)

The Nearctic species of Heterischnus Wesmael are revised. Redescriptions are provided of the three known species, H. bicolorator, H. huardi and H. coloradensis. Heterischnus mexicanus sp. nov. is newly described and H. bicolorator is recorded for the first time from the Nearctic region. The first key to the Nearctic species is provided along with species images and distribution maps.


Introduction
Heterischnus Wesmael (Hymenoptera: Ichneumonidae: Ichneumoninae) is a morphologically well-defined genus in the tribe Phaeogenini and is comprised of 30 described species in the Holarctic and Afrotropical regions (Yu et al. 2016). Heterischnus was formerly placed in the subtribe Heterischina (Diller 1981;Selfa and Diller 1994). However, Santos et al. (2021) found that the majority of the Phaeogenini subtribes were non-monophyletic and are therefore not recognized here. Heterischnus species are parasitoids of microlepidoptera, especially Pterophoridae (Bragg 1970;Sedivy 1986;Diller and Shaw 2014). Rearing records from other groups, such as noctuids (Rudow
Color. Head black, except brownish-red mandibular apex. Antenna brown. Mesosoma black. Legs brownish-red with coxae and trochanters varying from black to dark brown, except for brown tarsomere 5. MS1 varying from 0.5 anterior black to dark brown with 0.5 posterior brownish-red, to entirely black; T2 varying from entirely brownish-red, to brownish-red with 0.1 posterior brown; T3 brownish-red with posterior 0.1 brown to dark brown; T4-7 dark brown to black. Wing membrane clear; veins light brown.
Mesosoma. Mesonotum smooth with coarse punctures separated by 0.1-0.5× their diameter. Scutellum smooth with dense, coarse punctures separated by 0.2-1.0× their diameter. Mesopleuron varying from densely, coarsely punctate to rugulose-punctate. Speculum coarsely punctate dorsally. Ventral division of metapleuron densely, coarsely punctate to rugulose-punctate. Dorsal division of metapleuron finely punctate. Propodeum rugulose. Propodeal carination complete, except lateral longitudinal carina obsolete anteriorly. Tarsal claws simple.   Alaska, Umiat;20.vii.1947;C. Schultz;USNM. Distribution and biology. Heterischnus bicolorator is known from western Europe and as far east as Chita Oblast in Russia (Yu et al. 2016). In the Nearctic, it is known only from two localities in Alaska and British Columbia (Fig. 3), but is likely present throughout the intervening areas, including the Yukon Territory. No host information is known.
Comments. The three Nearctic specimens examined agree with both the original description (Aubert 1965) and images of a syntype specimen. No significant color or morphological differences could be found that would indicate that the examined Nearctic specimens are not conspecific with Palearctic specimens of H. bicolorator.
Material    Distribution and biology. Collecting dates span mid-May to early September, although the greatest number of records are from July and August. Heterischnus coloradensis occurs from the Rocky Mountains west to the eastern slopes of the Sierra Nevada Range (Fig. 6). Throughout its range, H. coloradensis is sympatric with H. huardi. No host information is known.
Comments. In addition to the examined paratype, a specimen that was compared with the holotype by Henry Townes was examined.  Townes (1944). Not examined.

Diagnosis.
Heterischnus huardi can be distinguished from other Nearctic species by the combination of the following: 1) clypeus yellowish-white in males; 2) female flagellum without any trace of yellowish-white banding; 3) supra-antennal area smooth with fine, shallow punctures; 4) and first lateral area of propodeum varying from entirely smooth to smooth and rugulose, but never rugulose-punctate as in H. coloradensis. Description. Female (Fig. 7). Body length: 5.5-8.8 mm; fore wing length: 3.8-5.6 mm.
Color. Head usually black, infrequently varying from dark reddish-brown to dark brown. Mandible yellowish-white except for dark brown apex. Antenna brown. Mesosoma overall black to dark brown, with the following areas yellowish-white: dorsal margin of pronotum, subalar prominence, and tegula; specimens from California and Oregon usually with mesonotum, scutellum, mesopleuron, and ventral division of metapleuron brownish-red to varying extents. Fore and middle legs with coxae, trochanters and trochantelli white to light reddish-brown; tibiae and femora light reddish-brown; tarsomeres 1-4 light reddish-brown; tarsomere 5 brown. Hind leg with coxa and trochanter light reddish-brown; trochantellus white to light reddish-brown; femur light reddish-brown; tibia light reddish brown with apical 0.5 dorsally brown; tarsomere 1 brown with basal 0.3 varying from light reddish-brown to brown; tarsomeres 2-5 brown. Metasoma varying from dark brown to black; one specimen from Nojoqui Falls Park, California with T1 medially brownish-red. Wing: membrane clear; basal 0.2 of wing with veins white, remaining vein sections brown.

Ire River
Comments. The color pattern of H. huardi varies throughout it range. The usual color pattern consists of a dark brown to black head, mesosoma, and metasoma, excluding white markings. Along the Pacific coast in Oregon and California, specimens exhibit varying degrees of brownish-red color on the mesonotum, scutellum, mesopleuron, and ventral division of the metapleuron.
Without stating any supporting evidence, Valemberg (2014) listed Ischnopsidea alberta Cushman and Phaeogenes recticaudus Provancher as subspecies of H. huardi. The elevation of these names from synonymy to subspecific status is unwarranted. There is no indication from the material examined in this study that any subspecies of H. huardi can be delimited.
The lectotype of H. huardi was not examined, although a specimen that was compared with the lectotype by Townes was examined.
Color. Head black, except following areas white: mandible except for brown apex, venterolateral corners of clypeus, and small ovoid adjacent to eye in supra-antennal area; clypeus varying from black to brownish-red; supraclypeal area brown in one specimen; flagellum brown, flagellomeres 7/8-11/12 with ventral surfaces white. Mesosoma overall brownish-red; anterior margin of pronotal collar, dorsal margin of lateral area of pronotum, subalar prominence, and tegula, white; following areas can be dark brown to fuscous: dorsal 0.5 of propleuron, more or less all of remaining non-white areas of pronotum, dorsal region of mesopleuron immediately below tegula, posterior margin of mesoscutum, metanotum, dorsal division of metapleuron, and propodeum.   Distribution and biology. Heterischnus mexicanus sp. nov. is the southernmost ranging Heterischnus species in the New World. Its range spans from the southern border of the USA in Arizona and Texas south to central Mexico in Tehuacán (Fig. 11). Records indicate that adults are active from late July to October and are likely active later in the year in the southern portion of its range as the latter date is from Tehuacán, Mexico. No host records are known for H. mexicanus.
Comments. As in H. coloradensis and H. huardi, a few specimens of H. mexicanus sp. nov. show an overall lighter coloration.
Etymology. This species epithet refers to its distribution, the majority of which is in Mexico.