Colpixys, Xiphentedon and morphologically similar genera

The genera Colpixys and Xiphentedon are similar and likely related to Entedon, but differ mainly in the morphology of the mesosoma, in particular in the median area of the propodeum. In both genera the median carina, which is the key diagnostic character for Entedon, is replaced by a median strip or furrow varying in shape and sculpture. Also, there are other features of head and mesosoma which either suggest relationships between or being critical for differentiation of the mentioned above genera. A review of some key characters is provided below, ranging from the propodeum to the head.

Propodeum (Fig. 1)

The main characters distinguishing Entedon, Xiphentedon and Colpixys from each other concern the structure of the propodeum. The possession of the complete median propodeal carina (Fig. 1A–C, mc) has been considered as diagnostic for Entedon (Erd̂s 1944; Graham 1963, 1971; Bouček 1988).

The median carina is a keel-shaped structure stretching from the anterior to the posterior edge of the propodeum (Fig. 1A–C, mc). It may slightly bifurcate anteriorly (Fig. 1C, mc) or disappear posteriorly in a raised coarse reticulation (Fig. 1B) in Entedon . In most Afrotropical, Indo-Malay, Australian and some Holarctic species, the carina is surrounded by groove-like channels on the sides (Fig. 1C, lc). This carina is absent in the described species of Xiphentedon (Fig. 1D) and Colpixys (Fig. 1F) and, correspondingly, in all the new species described below.

The median propodeal area of Colpixys and Xiphentedon may appear in one of three different configurations: (1) smooth flat strip delimited by nearly straight carinae (Fig. 1D, mstr); (2) shallow coriaceous strip delimited by fine carinae (Figs 18C–D, 19D, G); (3) sunken coriaceous furrow sharply delimited by raised borders (Fig. 1F, mf).

The coriaceous furrow sharply delimited by raised borders is diagnostic for both hitherto described species of Colpixys ( C. necator, Fig. 9A and C . gigas Bouček, 1972, Fig. 1F, mf), as well as for the below-described C. eburnus sp. nov. (Fig. 9B). The type species of Xiphentedon, X. kayovei, and most of the other (new) species gathered below into the kayovei -group, possess a smooth or light coriaceous median strip (of either broad V or Y shape) delimited by fine carinae on the median propodeum (Figs 1D, 13C, 14E). The coriaceous, distinctly margined strip (often Y-shaped) is found in some species described below under the proposed danielssoni and forceps groups of Xiphentedon (Figs 21C, 25D, 26E, 27D, 28A and others).

The median propodeal strip of Xiphentedon may or may be not homologous to the median propodeal furrow of Colpixys . On the one hand, this groove-like strip may appear homologous to the lateral channels occasionally flanking the median propodeal carina in Entedon (Fig. 1C, lc), i.e., being resultant from the secondary loss of the carina. On the other hand, the median strip may appear homologous to the median propodeal carina of Entedon (Fig. 1C, mc), being a derivation of a longitudinal split of its apical bifurcation. Both these hypotheses require independent verification.

The median furrow (or groove) is relatively rare in entedonines. It is present in a state similar to that of Colpixys in the genus Afrotroppopsis Gumovsky, 2007 (Gumovsky 2007: fig. 1c). It is also present in modified states in some species of Pediobius Walker, 1846, e.g., Р. ropalidiae (Risbec, 1958) (Fig. 1E), where the submedian carinae are nearly subparallel (Fig. 1E, smc), but weakly diverging posteriorly as in the majority of its congeners.

Another essential character, which has not been discussed for Entedon and allied genera, is the lateral propodeal sulcus (Fig. 1C–D). If the sulcus is complete, it surrounds the spiracular elevation and continues posteromedially to the supracoxal flange to the nucha, such that it delimits the submedian propodeal area laterally. The posterior part of the sulcus, referred to as the “channel between median panels and supracoxal flange” by Burks (2003), is often crossed by distinct costulae. The lateral propodeal sulcus is complete in many (chiefly tropical) species of Entedon (Fig. 1C, ls), in Xiphentedon kayovei and most new species attributed below to this genus (Fig. 1D, ls), and in some other genera (e.g., Proacrias Ihering, 1914). In most Holarctic species of Entedon and in Colpixys the sulcus is interrupted in its median part (Fig. 1A–B, F).

Thorax (Figs 2–4)

The pronotal shoulders, or “the postero-lateral expansions of the pronotum, which form a bump or protuberance” (Schauff 1988), or “lateral bullae” (Schauff 1991) have often been considered diagnostic for Entedon (Erd ̂s 1944; Graham 1963, 1971; Bouček 1988), and for Entedon and Colpixys (Schauff 1988) . This ‘shoulder’ represents a callus on the lateral panel of the pronotum (Fig. 2E–F, psh) in the above-mentioned genera. In most other entedonines the pronotum is smoothly curved, not forming any lateral swellings or protrusions. Similar, but not identical dorsal expansions of the pronotum are present in some other representatives of Entedoninae, for instance, in species of Apleurotropis Girault, 1913 (Fig. 3A, dsh), Pleurotroppopsis Girault, 1913 (Fig. 3C), Parahorismenus Girault, 1915, Paracrias Ashmead, 1904, Derostenus Westwood, 1833, and also in some Pediobius and others. The lateral protrusion (‘shoulders’) of the pronotum represent an expansion of the sharply delimited pronotal collar in these genera.

The pronotal shoulder of Entedon and allied groups is bordered by a semicircular ridge (or plica) below (Gumovsky 2002, 2011; Burks et al. 2011; Fig. 2, lpl), whereas the upper sector of the lateral panel of the pronotum bears no plica in most other entedonine genera. The pronotal ridge is situated in the upper sector of the lateral panel of the pronotum (Fig. 3E–F, lpl). The shape of the ridge also varies: it is semicircular in Entedon, Colpixys and Xiphentedon (Fig. 2, lpl), but nearly straight in the shape of a carina in Apleurotropis, Pleurotroppopsis, Chrysocharis Foerster, 1856, Achrysocharoides Girault, 1913 (Fig. 3, pcr) and some other genera.

One of the peculiarities of the lateral pronotal ridge of Entedon, Colpixys and Xiphentedon is its proximity to a sparse group of orifices near its anterior margin (Fig. 2, or). Similar orifices are present as a dense group in species of Pleurotroppopsis and Apleurotropis, which possess a transverse carina that is topologically similar to the lateral pronotal ridge mentioned above (Fig. 3). The nature and function of these orifices is unknown; they may be structures used in a sensory or secretory capacity.

The prosternum is the sclerite that is connected posteriorly to the propleuron and bears the prodiscrimen and the profurca (Yoder et al. 2010). This sclerite is exposed in Entedoninae and is visible as a diamondshaped structure due to divergent propleurae, unlike in the subfamily Eulophinae (Gauthier et al. 2000) . In most entedonines the prosternum is flat or, if convex, evenly curved. This condition is found in Colpixys, with the exception of C. eburnus sp. nov., whereas in Xiphentedon the prosternum bears a flange (occasionally with pubescence on the ventral surface) (Figs 22A, 27E–F, 36C–D, 38B–C). Similar prosternum shapes occur in some species of the putatively related genus Entedon .

The axillula has been considered to be an indistinctly defined and externally small area posterior to the axilla in the Chalcidoidea (Krogmann & Vilhelmsen 2006). No discernible structures, apart from small carinae or ridges, are generally reported for this area. However, occasionally the axilla bears a projection in some of the groups discussed below. This projection occurs in genera which are not closely related, i.e., Entedon (the tribe Entedonini of Entedoninae), Entedononecremnus Girault, 1915 (the tribe Euderomphalini of Entedoninae) and Trisecodes Delvare & LaSalle, 2000 (formerly unplaced within Eulophidae Westwood 1829, now in Systasidae Bouček, 1988; Burks et al. 2022). The shape of the projection is diverse and provisionally diagnostic at the species level for many Afrotropical, Oriental, Australasian and occasionally European species of Entedon, but also in Xiphentedon, as illustrated below. This projection bears two to five tooth-like indentations in these entedonines (for example, Figs 12F, 16C, 18D, 19G, 20F, 24G, 28B, D, 30D, 36F).

Another character is the shape and form of the transepimeral line. The transepimeral line separates the lower and upper parts of the mesepimeron (Gibson et al. 1997; Fig. 4, tps). The transepimeral line is sulcate in most Eulophidae, and particularly in the majority of Entedoninae (Fig. 4E–F, tps). However, in Entedon, Xiphentedon and Colpixys this sulcus is absent, and the delimitation of the lower mesepimeron is traceable only by the change in sculpture (Fig. 4A–D, lep 2).

A further character is the size (surface area and length) of the metascutellum. Most Entedonini of Entedoninae possess a comparatively long metascutellum, distinctly visible in dorsal view. The metascutellum is semicircular in shape in most species of Entedon (Fig. 1A–C, msc) and Colpixys (Fig. 1F, msc). However, in the specimens examined of the subgenus Cederholmia of Entedon, in X. kayovei, and also in some new species described below, the metascutellum is reduced to a narrow bar which is barely discernible in dorsal view (for example, Fig. 1D).

Head (Figs 5–7)

The V-shaped or transverse frontal sutures (frontal sulcus: Graham 1959, 1971; frontal grooves/sutures: Schauff 1988, 1991; the transverse facial sulcus: Burks et al. 2011; Fig. 5) is found in most of the Entedonini, and is likely one of the morphological synapomorphies for Entedoninae (e.g., Schauff 1991). Although the sutures are reduced in many species of Entedon (a secondary loss: Schauff 1988; Fig. 6C–D), they are distinctly traceable in some species of this genus (Fig. 6A–B) and in all species classified below as either Colpixys or Xiphentedon (Fig. 6E–F).

The non-sulcate scrobal grooves are conserved across genera and shared by Chrysocharis (Fig. 5D), Achrysocharoides (Fig. 5E–F), Entedon (Fig. 6A–D), and Derostenus (Schauff 1988) . Entedon and Achrysocharoides have been shown to be closely related (Gumovsky 2002; Burks et al. 2011). The genera Colpixys and Xiphentedon also possess these non-sulcate scrobal grooves (Fig. 6E–F), which may indicate their affinity to Entedon and Achrysocharoides . The anellus is defined as a small, narrow (or disc-like) flagellomere situated between the pedicel and the first funicular segment, or as the flagellomere that is located proximally on the flagellum and lacks longitudinal sensilla (Yoder et al. 2010). Schauff (1991) analyzed the number and conditions of anelli, which occur in Entedoninae and are proposed to distinguish the terminal anellus from the first funicular segment based on the absence (anellus) or presence (funicular segment) of the multiporous plate sensilla, apart from separation by size. Also, the possession of three anelli was considered a plesiomorphy for Entedoninae by Schauff (1991). The groups with three anelli ( Tropicharis Hansson, 1998) and with only one anellus ( Closterocerus Westwood, 1833, Chrysonotomyia Ashmead, 1904, Omphale Haliday, 1833 and Parzaommomyia Girault, 1915) were demonstrated to be a grade at the base of Entedonini by Burks et al. (2011).

Graham (1971) did not specify the number of anelli for Entedon, but mentioned one anellus only. Schauff (1988) mentioned that there are three anelli, with the first being largest in Entedon . However, Bouček (1988) also mentioned that Entedon has only one anellus. Waterston (1916) mentioned the “triple ring joint” (namely, three anelli) for Colpixys . Risbec (1957) did not mention the number and shape of anelli for Xiphentedon .

Species of Entedon (Fig. 7A–B), Colpixys (Fig. 7C–D) and Xiphentedon (Fig. 7H) indeed have three anelli: the notably and evenly enlarged first anellus, and two following anelli which taper dorsally, and thus the anelli appear subtriangular in shape (Fig. 7A–D, H). The third anellus is asymmetrical and its shape appears different when viewed from different angles (Fig. 7A–D). The third anellus is comparatively wide and bears trichoid sensilla when observed from the exterior view (Fig. 7A, D, H, a 3) in most species of Entedon, Colpixys and Xiphentedon . Occasionally, the third anellus is wider in this part than the entire first anellus (e.g., in Colpixys gigas, Fig. 7D, a 3). However, it is rather thin and hardly different from the preceding second anellus when seen from the interior (medial) view (Fig. 7C, a 3). The difference in size between internal and external aspects and also in the sensillar armoration of the enlarged anellus occurs in other genera too (Schauff 1991). For example, the structure of anelli described above is also inherent to Pleurotroppopsis podagrica (Waterson, 1925) (Fig. 7G). In addition, the enlarged (terminal of the two) anellus in Mestocharis maculata (Foerster, 1841) bears numerous trichoid and even one asymmetrical basiconic peg sensillum (= sensillum ampulaceum: Fig. 7E–F).

This review of some key morphological characters of the discussed taxa indicates that a combined molecular and morphological phylogenetic assessment of relationships of Colpixys and Xiphentedon is necessary. Either of these groups may appear to be derived within Entedon, and that may require reconsideration of their taxonomic ranks in future. This report, however, addresses the species diversity of Colpixys or Xiphentedon in their revised concepts, with comprehensive morphological descriptions.

Key to the species of Xiphentedon Risbec, 1957 and Colpixys Waterston, 1916

1. Pronotum with protruding lateral shoulders (Fig. 2, psh); each shoulder is in the form of a convex callus in the upper sector of the lateral panel of the pronotum, and delimited by a semicircular plica beneath (Fig. 2, lpl); transepimeral sulcus is effaced (Fig. 4A–D) ................................................... 2

– Pronotum without bulging lateral shoulders surrounded by a distinct semicircular plica below; if similar structures are present, then in different combinations: either shoulders are present, not as bulges or bumps, but as expansions of the delimited pronotal collar (Fig. 3A, dsh), or the plica (semicircular or straight) is not delimiting a bulging shoulder from below; transepimeral sulcus present as a distinct groove (Fig. 4E–F) ................................................. other genera of Entedoninae

2. Propodeum with a single median carina (Fig. 1A–C, mc), nearly reaching the metascutellum, which is visible in dorsal view as a wide semi-circular plate (Fig. 1A–C, msc); frontal sutures are angulate (Fig. 6A–B, fs) or absent (Fig. 6C–D) ........................................................... Entedon Dalman, 1820

– Propodeum with median strip (Fig. 1D), or a deep furrow delimited by two submedian carinae or by pliciform borders (Fig. 1F) medially; metascutellum visible (Fig. 1F) or hardly discernible (Fig. 1D) in dorsal view; face with V-shaped frontal sutures (Fig. 6F, fs) .......................................................3 ( Xiphentedon Risbec, 1957 and Colpixys Waterston, 1916)

3. Metascutellum long, easily discernible in dorsal view (Fig. 1F, msc), if somewhat smaller, then semi-circular in shape (but not in the shape of a narrow bar: C. eburnus sp. nov., Figs 9B, 11F), and anterior margin of mesoscutellum without a paired anteromedian protrusion; propodeum (Figs 1F, 9A–B): with median furrow represented by a deep sunken area, delimited by sinuous margins (Fig. 1F, mf), lateral propodeal sulcus incomplete, supracoxal flange with two to five setae posteriad of spiracular projection; axillula without a projection, at most with carinulae or plicae (Fig. 9C–D, F); gena evenly curved (Fig. 11D); metasomal petiole conical with margined, notably raised ‘roof’ dorsally in both sexes (Figs 8C, 10C, 11F); prosternum either evenly curved or with an arc traced by a carina, not a flange ............................................................................ 4 ( Colpixys Waterston, 1916)

– Metascutellum different: hardly visible in dorsal view, present as a narrow, bar-shaped strip (Fig. 1D, msc); propodeum with median smooth or coriaceous strip in the shape of a Y (Fig. 18C) or broad V (Fig. 1D), distinctly delimited by fine carinae which diverge anteriorly; lateral propodeal sulcus complete (Fig. 1D, ls): if not ( X. acutigena sp. nov., Fig. 38D), then anterior margin of mesoscutellum with a paired anteromedian protrusion (Fig. 37B, D); supracoxal flange asetose; axillula with indentate projection (Figs 12F, 16C, 18D, 19G, 20F, 24G, 28B, D, 30D, 36F); shape of gena and metasomal petiole varies; prosternum planar: with a flange (often with pubescence on ventral surface) on its arc (Figs 22A, 27E–F, 36C–D) .......................6 ( Xiphentedon Risbec, 1957)

4. F1 of female about 6.0× as long as wide, F2 about 5.0× as long as wide; gaster of female 6.0–7.0× as long as wide, 2.2–2.3× combined length of head plus mesosoma, syntergum long, 6.0–7.0× as long as wide, parallel-sided (Fig. 10A); funicle of male five-segmented ....... C. gigas Bouček, 1972

– F1 of female 3.0–4.0× as long as wide, F2 2.0–3.0 × as long as wide; gaster of female at most 3.0× as long as wide, slightly longer than head plus mesosoma, syntergum sub-triangular, wider than long; male (when known) with three-segmented funicle and two-segmented clava......................... 5

5. Metascutellum long (about one-third the length of propodeum), with lateral margins outlined (Figs 8C, 9A); metasoma of female slightly longer than head plus mesosoma, about 2.0–3.0 × as long as wide (Fig. 8A–B); dorsal ‘roof’ of metasomal petiole about 0.4× as long as propodeum (Figs 8 С, 9A); prosternum evenly curved; tip of scape slightly darker than the remaining part of it; subcosta of submarginal vein with two to three dorsal setae; fore wing mostly transparent; male funiculars less than 3.0× as long as wide ............................................... C. necator Waterston, 1916

– Metascutellum short (about one quarter the length of propodeum), with lateral margins evenly curved (Figs 9B, 11F); metasoma shorter than head plus mesosoma (Fig. 11C, E), as long as wide or slightly wider than long; dorsal ‘roof’ of petiole about 0.3 × as long as propodeum (Fig. 11F); prosternum with a transverse carina or ridge on its arc; base of scape slightly darker than the remaining apical part (Fig. 11C–D); subcosta of submarginal vein with two dorsal setae; fore wing slightly infumate medially (Fig. 11A–C) ......................................................................................... C. eburnus sp. nov.

6. Anterior margin of mesoscutellum with a paired anteromedian protrusion (Figs 34B, 35D, 36E, 37B, D); median area of propodeum with coriaceous or lightly reticulate strip, borders of which diverge anteriorly (mostly broadly Y-shaped) and delimited by fine carinae or pliciform borders (Figs 33D, 34B, 35D, 36E, 37B, D); metasomal petiole short conical in female, long conical in male (when known)…7 ( forceps group of Xiphentedon)

– Anterior margin of mesoscutellum almost straight or evenly curved (Figs 16D, 25D, 32C), at most with weak indentation (Figs 19D, 30E) ............................................................................................ 9

7. Gena with a short acute spike (Figs 37E–F, 38A–B); scape pale, slightly darkened apically; fore tibia with two pale stripes, other tibiae pale (Fig. 37C); median strip of propodeum lightly reticulate, its delimitation fading posteriorly among coarse reticulation; lateral propodeal sulcus incomplete, interrupted medially (Figs 37B, D, 38D); axillular projection lamellate and multidentate (Fig. 38E); male antenna with a deep constriction between two terminal flagellomeres (clavomeres) ..................................................................................................... X. acutigena sp. nov.

– Gena smooth, without a spike; scape dark, mid and hind tibiae darkened not more than basally; median strip of propodeum coriaceous, stretching back to nucha; lateral propodeal sulcus complete ......... 8

8. Mid and hind tibiae darkened with just a narrow basal band (Fig. 33A), fore tibia with two traceable longitudinal pale stripes; median strip of propodeum nearly 2.0 × as wide anteriorly as posteriorly (narrowly Y-shaped) (Figs 33D, 34B) ................................................................... X. forceps sp. nov.

– Legs almost entirely dark (Fig. 35A); median strip of propodeum less than 1.5 × as wide anteriorly as posteriorly (Figs 35D, 36E) .............................................................................. X. gerardi sp. nov.

9. Larger species, usually more than 2.0 mm in length, head more than 2.0× as wide as long, gaster at least slightly longer than broad, median strip of propodeum of broad V (Figs 12E, 13C, 14E, 16D, 19D) or broad Y (Figs 18C, 20E) shape…10 ( kayovei group of Xiphentedon)

– Smaller species, usually less than 2.0 mm in length, head less than 2.0 × as wide as long, gaster mostly subcircular, median propodeal strip Y-shaped (Figs 21C, 24H, 25D, 26E, 27D, 29F) ......................................................................................15 ( danielssoni group of Xiphentedon)

10. Propodeal strip subtrapeziform with nearly straight carinae diverging anteriorly (broad V-shaped, Fig. 1D), posterior areas of propodeum mostly smooth; gaster elongate, funicular segments with short peduncles ................................................................................................................................11

– Propodeal strip Y-shaped, sculptured (Fig. 18C), posterior areas of propodeum light reticulate; gaster slightly longer than broad, funicular segments with dictinct peduncles ......................................... 14

11. Propodeal median strip coriaceous, submedian areas light reticulate posteriorly (Fig. 19D); gaster about 2.3× as long as wide (Fig. 19A), syntergum about 1.3–1.4 × as long as wide; anterior margin of mesoscutellum with very short median paired indentations (Fig. 19D); costal cell with three setae on ventral surface ................................................................................................... X. simoni sp. nov.

– Propodeal strip and submedian areas smooth ................................................................................. 12

12. Syntergum of female gaster somewhat wider than long (Fig. 17A, C, E); costal cell of fore wing asetose .................................................................................... X. halli (Gumovsky, 1997) comb. nov.

– Syntergum of female gaster at least 3.0 × as long as broad; costal cell of fore wing with a row of short hairs ................................................................................................................................................. 13

13. Syntergum of female about 3.0 × as long as wide (Fig. 16D); mid and hind tibiae darkened similarly: both not more than on their basal one-quarter to one-third (Fig. 15A–B); metasomal petiole of male with anterior collar, slightly longer than broad; costal cell of fore wing with three setae on ventral surfaсe .............................................................................................................. X. neserorum sp. nov.

– Syntergum of female at least 5.0× as long as wide (Fig. 14C); mid and hind tibiae differ in degree of dark coloration: hind tibia darkened not more than on its basal half, but mid tibia darkened on about basal ¾–+/5 (Figs 12A, 14A, C); metasomal petiole of male nearly 2.8 × as long as wide, without anterior collar; costal cell of fore wing at most with one to two setae on ventral side ............................................................................................................... X. kayovei Risbec, 1957

14. Antennal scape entirely dark, metallic; median propodeal strip abruptly narrowing posteriorly (Y-shaped: Fig. 18C), metasomal petiole long and robust, nearly 4.0× as long as wide (appears shorter if observed in dorsal view); gena nearly evenly curved (Fig. 18E); axillular projection with four to five denticles (Fig. 18D) ........................................................................ X. musimba sp. nov.

– Antennal scape pale basally; median propodeal strip gradually narrowing posteriorly (intermediate between broad Y- and V-shaped), metasomal petiole short conical (Fig. 20E); gena bulging; axillular projection with six denticles (Fig. 20F) ................................................................ X. dewittei sp. nov.

15. Antennal scape entirely dark, metallic ............................................................................................ 16

– Antennal scape at least partially pale .............................................................................................. 19

16. Metasomal petiole short, wider than long (Fig. 30E); gaster slightly longer than broad, ovate (Fig. 30C); mid and hind tibiae pale on posterior half (Fig. 30A, C); scape slender, but narrowing apicad, flagellum with short robust segments (Fig. 30F–G)................................ X. palabora sp. nov.

– Metasomal petiole robust, as long as or longer than broad (Fig. 27D) .......................................... 17

17. Interantennal space without a process (Fig. 27F) ........................................................................... 18

– Interantennal space with a narrow and sharp process (Fig. 22A, F) ............................................... 20

18. Hind and mid tibiae predominantly darkened, just their extreme tips pale (Fig. 29A); spur of hind tibia 1.2× as long as width of tibia; axillular projection with at least four teeth (Fig. 29E, H) ......... ............................................................................................................................ X. kivuensis sp. nov.

– Hind and mid tibiae dark on about their proximal halves, the rest pale (Figs 30A, C, 31B); spur of hind tibia not longer than width of tibia; axillular projection bidentate ............ X. wieringai sp. nov.

19. Scape dark with pale base (Fig. 32E) ...................................................................... X. nimba sp. nov.

– Scape entirely pale (Fig. 31D) .............................................................................. X. sangha sp. nov.

20. Head dorsally about 2.0 × as wide as long; dorsal interorbital distance about 1.5× median vertexal distance (Fig. 22F) ...................................................... X. danielssoni (Gumovsky, 1997) comb. nov.

– Head dorsally about 2.5× as wide as long; dorsal interorbital distance nearly 2.0× median vertexal distance (Fig. 24D) ............................................................................................ X. jeanyvesi sp. nov.