Enizemum Förster 1869

Klopfstein, Seraina, 2014, Revision of the Western Palaearctic Diplazontinae (Hymenoptera, Ichneumonidae), Zootaxa 3801 (1), pp. 1-143 : 49-50

Enizemum Förster 1869

Type species. Bassus tibialis Cresson 1868

Diagnosis. Enizemum species can easily be identified by the strongly converging and then only narrowly separated and parallel median dorsal carinae on the first tergite, a character that can even be discerned when the carinae are apically reduced, by their strong convergence on the basal half of the tergite.

Face coriaceous and matt, without vertical impressions, in females entirely black or with a yellow central patch, in males entirely yellow or black with yellow inner orbits and a yellow central patch. Clypeus with apical margin thin, with a basal elevation and impressed laterally, resulting in the central area being flat or convex and the lateral parts being concave. Antenna with apical flagellomeres longer than wide, in males usually with broad, barlike tyloids (except for E. schwarzi which has narrow tyloids) and without long setae. Mesoscutum without notauli; densely punctate and often background weakly to strongly coriaceous, yellow shoulder marks present or absent; mesopleuron densely punctate and often coriaceous; epicnemial carina strong and complete ventrally. Propodeum with carinae partly reduced, with areas only indicated or absent; propodeal spiracle inconspicuous; scutellum only carinate basally. Fore wing areolet usually present, but vein 3rs-m often unpigmented, sometimes absent; hind wing with 3–5 basal hamuli. Hind tibia black with a white base, white area usually more extended ventrally in males. Female metasoma strongly dorsoventrally depressed, tergites convex, without transverse impressions. First tergite with a pair of median dorsal carinae arising basally, converging to almost meeting each other on apical half of the tergite, but sometimes the carinae are weak or entirely reduced on apical half. Second and third tergites with spiracles dorsal, above lateral folds. Metasoma black or rarely orange. Ovipositor sheaths 0.3 times as long as hind tibia, often concealed below the apical tergites, parallel-sided and not compressed, about circular in cross-section, transversely truncate and open towards apex. Males with tergites 9 and 10 as separate sclerites, sternite 9 about 2 times wider than long, emarginated apically, thus forming two lobes, their outer corners rounded.

Phylogeny. Enizemum is most closely related to Syrphoctonus and Woldstedtius , with which it shares the shape of the clypeus. Although the monophyly of the genus has been confirmed by molecular methods only for E. ornatum and E. nigricorne , the distinct morphology suggests that this is indeed a natural group.

Distribution. Worldwide except Australasian. The 24 species currently known in this genus occur mostly in the Eastern Palaearctic and the Nearctic, but some species are only known from the Afrotropical, Neotropical and Oriengal regions.

Biology. Species of this genus have been reared from a variety of Syrphinae species, and at least the common Enizemum ornatum seems to have quite a broad host range (e.g. Rotheray 1984; Thirion 1994, but see notes under E. scutellare ).

Key to species

1. Antenna with 20 to 22 flagellomeres in both sexes. Female antenna orange to reddish brown at least on basal segments, with multiporous plate sensilla present on entire antenna, although often sparser ventrally. Median dorsal carinae on first tergite very long, almost reaching posterior margin, converging over basal half of first tergite, then more or less parallel, thus forming a quite distinct angle ( Fig. 14 E). Mesosternum entirely black in females and black with yellow markings in males. Subtegular ridge usually black. Male mesopleuron black and yellow, without orange markings....... Enizemum ornatum (Gravenhorst)

- Antenna 23 to 25, rarely with 22 flagellomeres, usually dark brown, very rarely reddish brown. Female antenna apical flagellomeres ventrally often devoid of multiporous plate sensilla, covered with a short velvety pile (cf. Fig. 5 ). Median dorsal carinae on first tergite various, sometimes as described above, but often weak or even absent on posterior half, often converging over most of the tergite, thus not forming a quite distinct angle (cf. Fig. 14 F). Mesosoma sometimes partly orange. Subtegular ridge usually marked with yellow. Male mesopleuron often orange below..................................... 2

2. Mesosoma, propodeum and metasoma mainly orange in both sexes. Male antenna with narrow, linear tyloids (cf. Fig. 13 H).................................................................................. Enizemum schwarzi Diller

- At most mesopleuron, mesosternum and metapleuron marked with orange, metasoma black. Male antenna with broad, bar-like to oval tyloids (cf. Fig. 13 I).............................................................................. 3

3. Median dorsal carinae on first tergite very long, almost reaching posterior margin, converging over basal half of first tergite, then more or less parallel, thus forming a quite distinct angle (cf. Fig. 14 E). Propodeum with carinae around basal area at least indicated, less so in males. In females, ventral area of apical flagellomeres evenly covered with plate sensilla. Male face entirely yellow, mesopleuron orange on at least lower half.............................. Enizemum scutellare (Lange)

- Median dorsal carinae on tergites 1 and 2 often partly reduced, usually converging about three quarters or less of the tergite length, and more evenly and roundedly converging towards each other (cf. Fig. 14 F). Propodeum often without any indication of basal area. Female antenna with ventro-apical area devoid of plate sensilla but with a short velvety pile (cf. Fig. 5 ). Mesopleuron with orange colouration usually absent or more restricted........................................... 4

4. Mesoscutum coriaceous between the very dense punctures. Mesosternum entirely black in females. (Male unknown)................................................................................. Enizemum nigricorne (Thomson)

- Mesoscutum smooth and shining between the punctures. Mesosternum often marked with orange, more so in males. Male face often with two black vertical lines below antennal sockets.............................. Enizemum tridentatum Dasch

Figures

FIGURE 5. Ventral area of antennomeres 14 to 16 of a female Homotropus dimidiatus showing short, cone-like structures and the absence of multiporous plate sensillae, which in turn are abundant on the lateral and dorsal sides of the flagellomeres. The scale bar represents 100 µm.

FIGURE 14. A. Phthorima compressa ♀, metasoma. B. Enizemum ornatum ♀, hind tibia. C. Enizemum ornatum ♂, hind tibia. D. Homotropus frontorius ♀, hind tibia. E. Enizemum ornatum ♀, first tergite. F. Enizemum nigricorne ♀, first tergite. G. Homotropus elegans ♀, first tergite. H. Homotropus sundevalli ♀, first tergite. I. Enizemum ornatum ♀, clypeus. J. Homotropus elegans ♀, clypeus. K. Fossatyloides gracilentus ♂, antenna. L. Fossatyloides gracilentus ♀, propodeum. M. Homotropus pictus ♀, propodeum. N. Homotropus crassicornis ♀, propodeum.

FIGURE 13. A. Diplazon multicolor ♀, metasoma. B. Diplazon pectoratorius ♀, propodeum. C. Tymmophorus obscuripes ♀, propodeum. D. Xestopelta gracillima ♀, mesoscutum showing colour pattern. E. Campocraspedon caudatus ♀, metasoma. F. Campocraspedon caudatus ♂, metasoma. G. Daschia brevitarsis ♀, metasoma. H. Homotropus nigritarsus ♂, antenna. I. Enizemum ornatum ♂, antenna.