Illidops Mason, 1981

Höcherl, Amelie, 2025, Revision of Holarctic Illidops Mason (Hymenoptera, Braconidae): A first step towards resolving a dark taxon and descriptions of three new species, European Journal of Taxonomy 1031, pp. 1-121 : 6-16

Genus Illidops Mason, 1981

Illidops Mason, 1981: 56 ( type species: Illidops butalidis (Marshall, 1889: 45) , by subsequent designation by Mason 1981: 56)

Diagnosis

The genus Illidops can be defined at present by its posterior smooth band of the scutellum interrupted centrally by a sculptured area ( Fig. 2A–E; although in very few species the sculpture is very weak, mostly limited to a small area on the anterior margin of the mesoscutellar bar or only consists of punctures, Fig. 2F–I); fore wing with vein R1 shorter than pterostigma (~0.3–0.9× (e.g., Figs 6G, 10F, 12F, 20F), with the exception of I. kostylevi (Kotenko, 1986) having R1 as long as the pterostigma ( Fig. 25E)), although a few species in the morphologically similar genera Apanteles , Dolichogenidea and Rhygoplitis share this character; propodeum usually strongly sculptured, sculpture mostly reticulate (e.g., Figs 6E, 12D, 31D 48E, 52D; although a few species may have a median, longitudinal carina in addition to the reticulate sculpture ( Figs 36A–D, 53C) and some other species may have variously reduced sculpture (e.g., Figs 10E, 25D, 26D, 38C, 56E, 58D, 61D), in extreme cases having an almost entirely smooth propodeum ( Figs 19D, 22C)); hind wing with entirely setose vannal lobe (in most species, e.g., Figs 33F, 50H); eyes convergent, at times strongly ( Fig. 3A–B; but many species just very slightly convergent ( Fig. 3C) or with parallel eyes ( Fig. 3D)); T3–T7 medially desclerotized and seemingly pushed forwards (e.g., Figs 6F, 12E, 14E, 28E; although some species do not have this feature and some species in the morphologically similar genera Apanteles , Dolichogenidea and Rhygoplitis share this character).

Remarks

Knowledge on the potential monophyly of Illidops or its relationship towards the morphologically similar genera Rhygoplitis , Napamus , Apanteles and Dolichogenidea is poor. Phylogenetic relationships among microgastrine genera have so far proved largely intractable both using morphology or molecular methods (or a combination of both), possibly a result of rapid ancient radiation ( Banks & Whitfield 2006; Whitfield & Kjer 2008; Whitfield et al. 2018). Analyses of phylogenetic relationships of microgastrine wasps either did not include species of Illidops ( Mardulyn & Whitfield 1999; Whitfield et al. 2002; Banks & Whitfield 2006) or had very limited sampling of Illidops and closely related genera ( Abdoli et al. 2024).

All species treated here are part of a taxon that Fernandez-Triana et al. (2020) considered the Apanteles group, an informal grouping of 26 genera that includes most, but not all of the Apantelini + Microgastrini tribes sensu Mason (1981). This Apanteles group is characterized by having mostly setose and relatively long ovipositor sheaths and the hypopygium with the ventral margin flexible and pleated. Within the Apanteles group, Illidops is part of a larger subgroup defined by the lack of a closed fore wing areolet.

The genus Illidops was erected by Mason (1981) with I. butalidis (Marshall, 1889) as the type species of the genus. Mason’s concept of Illidops upon description of the genus included three described species: A. butalidis (the type), A. szaboi Papp, 1972 (currently a junior synonym of I. mutabilis ( Telenga, 1955)) , and A. urgo Nixon, 1965 . He based his concept on Nixon’s concept of his butalidis -group; however, he did not include a large number of the species which Nixon (1965) previously had included: A. dion Nixon, 1965 (now a junior synonym of I. suevus ( Reinhard, 1880)) , A. electilis ( Tobias, 1964) , A. sophrosine ( Nixon, 1976) , A. contortus Tobias, 1964 (now a junior synonym of I. naso ( Marshall, 1885)) , A. cloelia ( Nixon, 1965) , and A. evander Nixon, 1965 (now a junior synonym of I. naso ). This discrepancy may be explained by the limited access that Mason may have had to types and other specimens from the Palearctic, which is lamented by Tobias & Kotenko (1986), who did not accept his subdivision of Apanteles in their key. Papp (1988) later integrated more Palearctic species into Illidops by adding species which he and Nixon had previously included in their butalidis - ( Nixon 1965, 1976; Papp 1981), suevus - ( Papp 1984) and vipio ( Papp 1981) groups. Papp himself describes his homologization of European species groups with Mason’s genera as a first step “bearing the errors and misunderstandings of a first endeavour” ( Papp 1988: 146). Fernandez-Triana et al. (2014b) provided an updated diagnosis for the genus, first including the character of the “band of rugosity centrally on the posterior edge of the scutellar disc”, which was more or less repeated by Fernandez-Triana et al. (2020). Two species were subsequently transferred to other genera, but most of the species remain in Illidops . Apanteles biroicus Papp, 1973 was transferred back to Apanteles by Fernandez-Triana et al. (2020), and Napamus vipio ( Reinhard, 1880) became the type of the genus Napamus , described by Papp (1993).

The characters defining the genus were re-examined by Fernandez-Triana et al. (2014b) who noted that the lower margin of the eyes converging and metasomal terga 3–7 weakly sclerotized were absent in several species; they proposed a modified definition of Illidops that focused on the “band of rugosity centrally on the posterior edge of the scutellar disc”, shortened fore wing vein R1 and propodeum fully sculptured but without areola (instead, with a series of short carinae medially on the posterior 0.2–0.3 of the propodeum near the nucha). The previous definitions by Mason (1981) and Fernandez-Triana et al. (2014b) were more or less repeated and combined in the world checklist of microgastrine wasps ( Fernandez-Triana et al. 2020: 39).

For the present study, we had access to many additional specimens and species, including types and photos of types of several species which had neither been studied by Mason nor by Fernandez-Triana. Our study of those specimens suggests that the definition of Illidops is more complicated than anticipated, even if only restricted to Holarctic species. The main challenge was that we found more variation in the sculptured area interrupting the posterior smooth band of the scutellum centrally than described by previous authors and some species lacking it completely or almost completely. The degree of convergence of the lower margins of the eyes also varies amongst species of Illidops and in some the eyes do not converge. Both characters and their shortcomings are detailed more in a separate section below. Some species of Illidops are hence difficult to clearly place as they combine a set of features characteristic of other genera, e.g., Dolichogenidea (cosmopolitan), Rhygoplitis (NEA, NEO) , and Napamus (PAL) . The separation of these four genera can be challenging for some species. Table 1 provides a comparison between these genera.

Napamus (a genus currently with only two described species) lacks most of the key characters present in Illidops and the two genera should almost always be easily distinguished ( Ghafouri Moghaddam et al. 2021).

Rhygoplitis has some features that resemble some species of Illidops , e.g., fore wing R1 short, sculptured area interrupting the posterior smooth band of the scutellum centrally, and propodeum coarsely sculptured and with a median, longitudinal carina ( Mason 1981; Whitfield 1997). Additionally, the few DNA barcodes available for Rhygoplitis tend to cluster with sequences of Illidops in NJ analyses. Rhygoplitis has rather strongly defined notauli and the overall body sculpture very coarse; it is also a genus so far only known from the Neotropics and the Nearctic (mostly southern areas).

The vast majority of species of Dolichogenidea can easily be distinguished from Illidops because all of its species have an entirely smooth band posterior to the scutellum; also the propodeum is very rarely strongly sculptured and, when sculptured, usually not in the common patterns found in Illidops . These two genera usually cluster far apart in NJ topologies of Microgastrinae (e.g., Smith et al. 2013), although the definition of Dolichogenidea is far from resolved (see Mason 1981; Fernandez-Triana et al. 2014b; 2020). However, a few species of Illidops that we have examined as part of this study have a very weak (sometimes almost absent) sculptured area interrupting the posterior smooth band of the scutellum centrally, and in those species the propodeum is also not strongly sculptured (it is either entirely to mostly smooth or at least smooth on the anterior half of the propodeum). Those few species strongly resemble Dolichogenidea – although their sequences still tend to cluster with more ‘typical’ Illidops in NJ analyses. Nevertheless, these species with an almost entirely smooth band posterior to the scutellum and smooth propodeum challenge the concept of Illidops and it may be found in the future that they are better placed in a different genus. This concerns especially I. bellicosus ( Papp, 1977) and I. perseveratus ( Papp, 1977) . Illidops suevu s also has the posterior band of the scutellum almost entirely smooth but has a strongly sculptured propodeum. For this paper we decided to include them in Illidops based on the short vein R1, elongate mouthparts and (in the case of I. suevus ) the clustering of their sequences.

Shortcomings of some characters used for the identification of Illidops Mason, 1981

Area of rugosity posterior to the scutellum

The character “posteriomedian band of rugosity” refers to an area of rugosity posterior to the smooth, at most punctate scutellum and was introduced for Illidops by Fernandez-Triana et al. (2020). Nixon refers to this as “posterior polished band of scutellum interrupted at middle by small patch of rugosity” ( Nixon 1976: 709). After examining many species of Illidops , we prefer to refer to this as “posterior smooth band of the scutellum more or less interrupted centrally by sculptured area”. This may range from a clearly visible area of rugosity centrally posterior to the scutellum which also invades the smooth band posterolaterally, such as in I. scutellaris ( Muesebeck, 1921) and I. cf. naso ( Fig. 2A–B), to a somewhat intermediate state in which the sculpture may be an area of rugosity or punctation which is restricted only to the central part posterior to the scutellum, as in I. cf. mutabilis ( Telenga, 1955) , I. butalidis , and I. splendidus ( Papp, 1974) ( Fig. 2D–F). In other species, the sculpture does not reach the posterior half of the smooth band entirely, but it seems that the sculpture and punctation of the scutellum invade the smooth posterior band slightly anteriorly, such as in I. doreenae Höcherl & Fernandez-Triana sp. nov., I. oroseira Höcherl & Fernandez-Triana sp. nov. and I. suevus ( Fig. 2F–G). This is clearly different from the very smooth area posterior to the scutellum present in many other genera, such as Apanteles ( Fig. 2H). However, this character can also vary within a single species and barcoding cluster (MOTU), as is the case in I. oroseira . It is also difficult to observe in some species, such as I. suevus . The character is not always clear-cut and does not separate Illidops from other genera alone, although it is not present in other closely related genera which may potentially be confused with Illidops , such as Apanteles , Dolichogenidea , Napamus and Rhygoplitis . Fernandez-Triana et al. (2020) transferred Apanteles biroicus from Illidops to Apanteles based on the lack of the sculptured area centrally interrupting the posterior smooth band of the scutellum and the different propodeum sculpture compared to other members Illidops ; in light of our findings, this species may need to be reassessed in the future.

Eyes converging towards lower margin of the face

Several authors who published on the butalidis- group used the degree of convergence of the eyes towards the lower margin of the face as a character in their keys ( Nixon 1976; Papp 1981; Tobias & Kotenko 1986). This character varies among the species of Illidops , some clearly show strongly converging inner margins of the eyes, in which case the minimum face width is less than 0.85 × the upper face width. This includes species such as I. butalidis ( Fig. 3A), I. splendidus , I. terrestris Wharton, 1983 , I. toreicus Kotenko, 2007 , I. urgo ( Nixon, 1965) , I. urgens Kotenko, 2004 , I. naso , and I. vitobiasi Kotenko, 2004 ( Fig. 3B). In these cases, the eyes can also appear somewhat bulging, especially on the lower part of the head. In other cases, the eyes are only slightly converging with the minimum face width measuring ~0.85–0.95× the upper face width ( Fig. 3C). This includes species such as I. buteonis (Kotenko, 1986) , I. cloelia , I. dauricus Kotenko, 2007 , I. kostjuki (Kotenko, 1986) , and I. subversor . Species with almost parallel inner eye margins have a minimum face width of ~0.95–1.05 × the upper face width ( Fig. 3D). This includes species such as I. blandus ( Tobias & Kotenko, 1986) , I. suevus , and I. suffectus ( Tobias & Kotenko, 1986) . For practical reasons and for measuring the degree of convergence of the eyes, it appears useful to us to compare the upper face width to the minimum face width rather than lower face width, which in many cases can be done as a proxy for lower face width as the result will be the same. In addition to challenges in measuring this character, it is a continuous character with no discrete values, and can hence not really be categorized in a meaningful way. It can only be used for species which are significantly different and such comparisons should always include a measurement of the face width of the species. We are using the character here, with the above reservations, as it has proven useful in the past. For this character in our key, we will use the terminology as detailed above: strongly converging=minimum face width <0.85× upper face width; slightly converging=minimum face width ~0.85–0.95 × upper face width; not converging=minimum face width ~0.95–1.05 × upper face width.

Triangle delimited by the ocelli

Another character frequently used to distinguish species of Illidops is the shape of the triangle formed by the ocelli. The triangle can be either ‘obtuse’/’very low’, ‘less low’ or ‘high’, which is measured by whether an imaginary tangent posterior to the anterior ocellus crosses the posterior ocelli (illustrated in Fig. 1). If the tangent crosses the posterior ocelli, the triangle is obtuse/very low, such is the case in I. blandus and I. mutabilis ( Fig. 4A), and according to Tobias & Kotenko (1986) also in I. rostratus ( Tobias, 1976) . If the tangent does not touch the posterior ocelli the triangle is high, such as in I. vitobiasi ( Fig. 4D), I. buteonis , I. cloelia , I. suevus , and more. Some species exhibit an intermediate state which is difficult to interpret and in which the tangent touches the posterior ocelli, such as in I. toreicus and I. subversor ( Tobias & Kotenko, 1986) ( Fig. 4B–C), forming a higher triangle. This is also influenced by the size of the ocelli (ocelli diameter=OD), which can vary as well ( Fig. 4C–D).

Shape of tergite 2

The shape of T2 has been variously interpreted in historical references. Nixon used it in his 1976 key to distinguish between I. cloelia and A. evander (now a junior synonym of I. naso ). Nixon refers to the acuteness of the posterolateral angles in couplet 8 as follows: “almost right-angled” for I. cloelia ( Fig. 16E) and “acutely drawn out” ( Nixon 1976: 709) for A. evander / I.naso ( Fig. 5A–D). Kotenko uses this character in his 2007 key to distinguish I. dauricus and I. kostjuki from I. naso and I. assimilis ( Papp, 1976) . He uses two characteristics regarding the shape of T2: 1) how much T2 narrows towards the base (“less narrowed” in I. dauricus and I. kostjuki ( Fig. 5E–F) and “more narrowed” in I. naso and I. assimilis ( Fig. 5A–D, 7E)) and 2) the shape of the posterolateral angles (“almost straight” in I. dauricus and I. kostjuki ( Fig. 5E–F) and “distinctly drawn into points” ( Kotenko 2007: 179) in I. naso and I. assimilis ( Figs 5A–D, 7E)). We found the posterolateral angles rather difficult to interpret and even observed bilateral variation in some specimens ( Fig. 5C–D). The varyingly sinuate posterior margin of T2 also adds to this and we are not sure if this character can be reliably used to distinguish species of Illidops ; it might need to be re-evaluated. The interpretation of the anterior margin in I. kostjuki and I. dauricus is complicated by anterolateral smooth sclerotized protrusions of the median field with pointed corners which make it difficult to observe the exact limits of the anterior margin of T2.

Identification key to females

1. Propodeum with complete median carina in addition to reticulate sculpture all over ( Figs 36A–D, 53C) .................................................................................................................................................. 2

– Propodeum without median carina, sculpture variable but very rarely propodeum completely reticulate ........................................................................................................................................... 3

2. Body color mostly yellow-orange or yellow-brown; T1 strongly widening towards posterior margin ( Fig. 53; Kazakhstan) ...................................................... I. suffectus ( Tobias & Kotenko, 1986) ***

– Body color black to dark brown; T1 subrectangular to slightly barrel-shaped; BOLD:AEO8226 ( Figs 35–36; Germany) ................................... I. oroseira Höcherl & Fernandez-Triana sp. nov. ***

3. Body, including head, pale (brownish-red or brownish-yellow) ( Fig. 10; Tajikistan) ....................... ............................................................................................ I. blandus ( Tobias & Kotenko, 1986) ***

– Body mostly, head always, dark (black or dark brown) ................................................................... 4

4. Clypeus either entirely yellow or light brown, contrasting with darker face ( Figs 58B, 59B); AND propodeum shiny, smooth or weakly sculptured (but at least with central smooth area; Fig. 58D) ... ........................................................................................................................................................... 5

– Clypeus dark brown or black, similar in color to face; IF rarely lower half of clypeus yellow-brown (lighter colored than upper half of clypeus and face) THEN propodeum entirely or mostly strongly sculptured .......................................................................................................................................... 7

5. Glossa elongate; eyes very slightly converging below, lower face width ~0.93 upper face width, eyes not seemingly bulging; clypeus light brown; scape and pedicel dark brown to black; BOLD: AAB5165 ( Figs 19–21; Nearctic: Canada) ... I. doreenae Höcherl & Fernandez-Triana sp. nov. ***

– Glossa of normal proportions; eyes strongly converging below, lower face width <0.85 upper face width, eyes seemingly bulging; clypeus yellow to bright yellow; scape and pedicel yellow to light brown (Palearctic) ............................................................................................................................. 6

6. Posterior smooth band of the scutellum clearly interrupted centrally by sculptured area ( Fig. 58D, also compare Fig. 2A–E); darker legs including black or dark brown metacoxa; anteromesoscutum comparatively duller, having a matte appearance ( Fig. 58; Kazakhstan, Russia (SAR)) ................................................................................................... I. urgens Kotenko, 2004 ***

– Posterior smooth band of the scutellum entirely smooth ( Fig. 60D, also compare Fig. 2J); legs mostly lightly colored to yellow and metacoxa almost yellow; anteromesoscutum comparatively smoother and shinier ( Figs 59–60; Armenia, Azerbaijan, Croatia, Greece, Hungary, Iran, Mongolia, Russia (S), Slovakia, Turkey) ...................................................................................... I. urgo ( Nixon, 1965) ***

7. T2 more or less rectangular, lateral margins more or less parallel-sided; AND posterior margin almost straight; AND T2 width at posterior margin less than 2.5 × its central length; AND T1 more or less parallel-sided with posterior margin sinuate ( Fig. 57; Russia (ZAB)) ............................................... ............................................................................................................. I. toreicus Kotenko, 2007 ***

– T2 either trapezoidal, subtriangular or very narrowly rectangular, lateral margins often not parallel-sided; AND/OR posterior margin usually sinuate; AND/OR T2 width at posterior margin>3.0 × its central length; AND/OR T1 differently shaped ................................................................................ 8

8. Scape flattened; hypopygium short, ending far before apex of metasomal terga ( Russia (DA)) ................................................................................................. I. planiscapus ( Tobias, 1976) *

– Scape not flattened; hypopygium variable ........................................................................................ 9

9. T1 strongly widening towards posterior margin (T1 width at posterior margin>1.5 × its width at anterior margin); AND hypopygium very short, ending far before apex of metasomal terga ........ 10

– T1 not as strongly widening towards posterior margin; AND/OR hypopygium longer, ending at or beyond apex of metasomal terga .....................................................................................................11

10. All coxae pale (yellow to reddish-yellow or yellow-brown), at most infuscate basally; propodeum reticulate; T1 and T2 coarsely rugose; maxillary palps brown to light brown ( Figs 48–52; widely distributed across the Palearctic) ........................................................ I. suevus ( Reinhard, 1880) **

– At least metacoxa entirely dark (dark brown to black); propodeum uniformly rugose; T1 and T2 punctate to weakly rugose; maxillary palps bright yellow ( Fig. 47; Russia (NVS)) ........................................................................... I. subversor ( Tobias & Kotenko, 1986) ***

11. Scape, pedicel, first few flagellomeres, and most of legs (except for metacoxa) yellow to yellow-brown, rest of body black; AND pterostigma with anterior 0.4 yellow (yellow portion transverse); AND ovipositor sheaths much shorter than metatibia (~0.5) ( Fig. 61; Turkmenistan) ...................... ............................................................................................................ I. vitobiasi Kotenko, 2004 ***

– Antenna and legs entirely or mostly dark brown to black; AND/OR pterostigma without large pale area; AND/OR ovipositor sheaths longer than half metatibia length ............................................. 12

12. Ocelli in very low triangle, almost in straight line, posterior tangent to anterior ocellus cutting deeply into posterior ocelli ( Fig. 26B, also compare Fig. 4A) ................................................................... 13

– Ocelli always in high triangle, posterior tangent to anterior ocellus at most almost touching posterior ocelli (compare Fig. 4D) ................................................................................................................. 14

13. Eyes at most slightly converging, lower face width ~0.91 upper face width; T2 short, length ~0.25 width; mouthparts elongate ( Armenia, Russia (KDA), Uzbekistan) ..... I. rostratus ( Tobias, 1976) *

– Eyes strongly converging, lower face width ~0.83 upper face width; T2 longer, length ~0.33 width; mouthparts not as elongate ( Fig. 26; widely distributed in the Palearctic) ......................................................................................... I. mutabilis ( Telenga, 1955) **

14. T1 strongly narrowing towards posterior margin (anterior margin width about 1.5 × posterior margin width); AND T2 subtriangular, very short; AND T2 posterior margin strongly sinuate; AND wings rather strongly infumate ( Fig. 56; Tajikistan, Turkmenistan) ............... I. tigris (Kotenko, 1986) ***

– T1 not as strongly narrowing towards posterior margin (anterior margin width <1.5 × posterior margin width); AND/OR T2 either broadly trapezoidal or rectangular; AND/OR T2 margin straight; AND/OR wings hyaline .................................................................................................................. 15

15. Propodeum smooth or almost smooth, shiny at least on upper half (e.g., Figs 22C, 25D) ............ 16 – Propodeum entirely densely sculptured, matte ............................................................................... 19

16. Fore wing vein R1 very short, <0.5× pterostigma length .............................................................. 17 – Fore wing vein R1 longer, clearly> 0.6× pterostigma length ........................................................ 18

17. Ovipositor sheaths shorter than metatibia; T1 broad, parallel-sided up to posterior 0.3, only slightly narrowing posteriorly afterwards; T1 posterior width about 2 × T2 length; 1 st antennal flagellomere pale, contrasting with remaining darker flagellomeres ( Fig. 9; Mongolia) ............................................................................................. I. bellicosus ( Papp, 1977) **

– Ovipositor sheaths longer than metatibia; T1 gradually narrowing towards posterior margin; T1 posterior width <2 × T2 length; antennal flagellomeres not contrasting ( Fig. 37; Mongolia) ......................................................................................... I. perseveratus ( Papp, 1977) **

18. Pterostigma with comparatively large pale spot at base (brownish-yellow on anterior 0.2), rest of pterostigma brown; clypeus slightly lighter than face; eyes strongly converging, lower face width ~0.8 × upper face width ( Figs 22–23; Croatia, Hungary, Kazakhstan, Russia (S), Serbia, Tunisia) ................................................................................................ I. electilis ( Tobias, 1964) ***

– Pterostigma entirely to mostly dark brown, at most with small, faint, pale spot at base; clypeus same color as face; eyes are at most slightly drawn close together, lower face width ~0.9 × upper face width ( Fig. 25; Russia (ROS), Ukraine) ................................................... I. kostylevi (Kotenko, 1986) ***

19. Eyes drawn very close together downwards, lower face width <0.85 × upper face width (compare Fig. 3A–B); malar distance very short ( Figs 6A, 12B, 14B, 44B, 54B) ......................................... 20

– Eyes not drawn close together or only slightly drawn downwards, lower face width> 0.86 × upper face width (compare Fig. 3C–D); malar distance usually longer ................................................... 23

20. T1 strongly narrowing towards posterior margin (anterior margin width 2× posterior margin width); T2 more or less trapezoidal in shape, T2 width at posterior margin more than 3.0 × its width at anterior margin ( Figs 54–55; NEA: USA (CA, FL, GA, TX)) ......... I. terrestris Wharton, 1983 *** – T1 more or less barrel-shaped or parallel-sided, anterior margin about same width as posterior margin width; T2 not trapezoidal in shape, either subquadrate or transverse, T2 width at posterior at most 2.0× its width at anterior margin (usually much less) .................................................................... 21

21. T1 comparatively narrower and longer, its length more than 1.5 × its maximum width; T2 almost as long as T3; face comparatively narrow, its maximum width approximately equal to its height; BOLD:ACQ9731, BOLD:AEL7562, BOLD:AEI6389 ( Figs 12, 14; widely distributed in the Palearctic) ....................................................................................... I. butalidis (Marshall, 1889) *** – T1 comparatively wider and shorter, its length 1.2–1.3 × its maximum width; T2 much shorter than T3; face comparatively wider, its maximum width much greater than its height ........................... 22

22. Pterostigma mostly brown, with pale spot at anterior 0.3; metafemur dark brown, contrasting with mostly light, yellow-brown metatibia (metatibia only with dark spot on posterior 0.2); anteromesoscutum smooth, somewhat shiny, with punctation rather fine; BOLD:AEJ7519 ( Fig. 44; Germany, Hungary, Russia (C)) ......................................................... I. splendidus ( Papp, 1974) ***

– Pterostigma very pale, mostly yellow-white, with thin brown margins; metafemur dark reddish-brown, same color as metatibia; anteromesoscutum matte, with coarse and deep punctures; BOLD:AAD8583 ( Fig. 6; Egypt, AFR: United Arab Emirates, Yemen) .................................................. I. albostigmalis van Achterberg & Fernandez-Triana, 2017

23. Metafemur lighter, reddish-yellow; AND all of the following characters: eyes slightly converging; antennae as long as body, preapical segment elongate; mesonotum densely punctate, almost matte; tegulae blackish; pterostigma brown with large pale spot from base to beyond middle; T1 comparatively wide, its length slightly more than its maximum width; ovipositor sheaths slightly shorter than metatibia; rather small, body length 1.9–2.2 mm ( Kazakhstan, Russia (S)) ................................................................................. I. nigritegula ( Tobias & Kotenko, 1986) **

– Metafemur darker, black or dark brown; IF rarely ( I. assimilis ) metafemur reddish-yellow, THEN remaining characters not as above .................................................................................................. 24

24. Head in frontal view elongate, malar distance 1.5 × as long as basal width of mandible; AND most of metasoma dorsally orange-yellow, contrasting with darker T1 ( Fig. 8; Spain) ..................................................................................... I. barcinonensis ( Marshall, 1898) ***

– Head in frontal view not as elongate, malar distance less than 1.5 × as long as basal width of mandible; metasoma dorsally entirely dark brown to black ........................................................... 25

25. Profemur (except for anterior 0.2 or less) light brown to yellow and all tibiae yellow ( Figs 7D, 38B); AND ovipositor sheaths clearly shorter than metatibia .................................................................. 26 – All femora (except for posterior half of profemur) and all tibiae (usually) dark brown to black; ovipositor sheaths of variable length .............................................................................................. 27

26. Pterostigma with pale basal spot; metafemur mostly brown; maxillary palps mostly pale (yellow-white); BOLD:AAA8769 ( Figs 38–40; species very widely distributed in AUS, NEA, NEO, PAL) ......................................................................................... I. scutellaris ( Muesebeck, 1921) ***

– Pterostigma entirely dark brown; metafemur mostly pale (yellow); maxillary palps mostly brown ( Fig. 7; Mongolia) ................................................................................... I. assimilis ( Papp, 1976) **

27. Ovipositor sheaths clearly shorter than metatibia (~0.8 ×); T1 usually shorter and parallel-sided, barely narrowing posteriorly ........................................................................................................... 28 – Ovipositor sheaths about same length as metatibia (~0.9–1.1 ×); T1 usually more elongate, barrel-shaped ............................................................................................................................................. 30 28. Metatibia entirely dark; BOLD:AEO8223 ( Fig. 16; species widely distributed in the Palearctic) ................................................................................................ I. cloelia ( Nixon, 1965) ** – Metatibia yellow with some infuscation on apical third ................................................................. 29

29. Glossa distinctly elongate; clypeus light/brown, contrasting with entirely black face; T1 narrowing; anteromesoscutum with deep, dense punctation, matte; fore wing vein 1M entirely pale; BOLD:AAC7888 ( Figs 45–46; NEA: Canada (YT)) ......................................................................... .............................................................. I. stefanschmidti Höcherl & Fernandez-Triana sp. nov. *** – Glossa not distinctly elongate; clypeus dark, same color as face; T1 barrel-shaped; anteromesoscutum with shallow punctation, shiny; fore wing vein 1M dark in basal 0.5 ( Fig. 24; Russia (ALT)) ......... .......................................................................................................... I. kostjuki (Kotenko, 1986) ***

30. Eyes comparatively large, laterally width of eye>2× as long as width of gena laterally (compare Fig. 41A–H); head in dorsal view distinctly wider than mesoscutum; T1 slightly narrowing posteriorly, 1.4–1.5 × as long as its maximum width; ovipositor sheaths about same length as metatibia; body length 2.8–3.0. mm ( Bulgaria, Hungary, Italy, Russia (ZAB, PRI)) .. I. sophrosine ( Nixon, 1976) * – Eyes comparatively smaller, laterally width of eye no more than 2× length of gena width laterally (compare Fig. 41I–L) (from here tentative key to the morphologically cryptic species of the I. naso complex, based on characters employed by previous authors. We noticed that some of these characters are variable and therefore might be insufficient to differentiate between these four species.) ...... 31

31. T1 and T2 almost smooth, only very lightly rugose; maxillary palps light brown to yellow; fore wing vein C light brown to yellow basally ( Fig. 15; Russia (S), Ukraine) ................................................. ...................................................................................................... I. buteonis (Kotenko, 1986) (***) – T1 and T2 rugose; maxillary palps brown; fore wing vein C brown basally ................................. 32

32. Found in Far East Russia ( type series from Transbaikal territory); median field of 2 nd abdominal tergite less narrowed towards base, posterolateral angles almost straight ( Fig. 17; Russia (ZAB)) ............................................................................................ I. dauricus Kotenko, 2007 (***)

– Widespread in Holarctic, mostly recorded from western Palearctic ( holotype from United Kingdom); median field of 2 nd abdominal tergite more narrowed towards base, posterolateral angles distinctly drawn into points ( Fig. 29; widely distributed in the Palearctic) ............. I. naso ( Marshall, 1885) *

Treatment of Holarctic species of Illidops Mason, 1981