Research Article
Research Article
New family-level characters for Platygastroidea
expand article infoIstván Mikó, Monique Raymond, Elijah J. Talamas§
‡ University of New Hampshire, Durham, United States of America
§ Florida Department of Agriculture and Consumer Services, Gainesville, United States of America
Open Access


Platygastridae (Hymenoptera) is a diverse family of parasitoid wasps for which few studies of internal morphology have been conducted. The monophyly of the group is undisputed based on recently published molecular data, but based on morphology, the family is diagnosable from other platygastroids only by a combination of character reductions. In the present study we explored the mesosoma of Platygastroidea and found two new synapomorphies for Platygastridae: an externally visible anterior mesofurcal pit, which corresponds to an invagination that connects to the anterior portion of the mesofurca, and internally, a posteriorly shifted origin of the first wing flexors. The absence of a mesofurcal bridge and the exclusively mesopectal origin of the fore wing flexors are treated as synapomorphies for Platygastridae+Janzenellidae. Phylogenetic implications and evolutionary hypotheses regarding these traits are discussed.


Fossils, furca, Janzenellidae, morphology, Platygastridae, Scelionidae


Platygastroidea (Hymenoptera, Proctotrupomorpha) are parasitoid wasps whose hosts represent ten insect orders and spiders (Austin et al 2005; Chen et al. 2021) and has been recently classified into eight families (Table 3; Chen et al. 2021). Platygastridae is highly diverse and extremely common with more than 2000 species worldwide ( Based on molecular analyses, Platygastridae is sister to Janzenellidae, but this relationship is yet to be supported by any morphological characters. Platygastridae currently contains two monophyletic subfamilies, Platygastrinae and Sceliotrachelinae (Chen et al. 2021).

Platygastrinae parasitize gall midges (Diptera, Cecidomyiidae) (Austin et al. 2005) and are known to be effective against new invasive and serious quarantine pests in North America, such as the Swede midge (Ferland 2020) and the apple leaf midge (He and Wang 2015; Cossentine et al. 2021). They are considered propitious natural enemies of the wheat midge (Echegaray et al. 2016; Chavalle et al. 2018; Dufton et al. 2021) and have potential utility in suppressing populations of the soybean midge as well (Harris 2019; Kee 2019). In contrast to Platygastrinae, sceliotrachelines are egg, nymphal, and larval parasitoids of multiple orders including Coleoptera, Hemiptera, and Hymenoptera (Chen et al. 2021).

Despite their economic importance, the systematics of Platygastridae at the species level is in major need of revision, characterized by a high number of superficially described species with incomplete or missing differential diagnoses (Buhl and Jałoszyński 2019; Buhl 2021). At the generic level, identification of platygastrines is nearly impossible for non-specialists due to a lack of comprehensive identification keys and inadequate generic concepts.

The monophyly of Platygastridae is strongly supported by a recent molecular analysis (Chen et al. 2021). Despite this strong support of monophyly, only three morphological synapomorphies have been proposed for the family: absence of a mesepimeral sulcus (Talamas et al. 2019), absence of the mesofurcal bridge (Heraty et al. 1994), and the absence of a netrion (Mikó et al. 2007). However, only the mesepimeral sulcus has been examined in a wide range of platygastrid taxa and on many specimens. In this study, we examined the skeletomuscular system of the mesosoma in a range of extant and fossil platygastroids to better characterize these and other traits, and to explore to what degree they are phylogenetically informative.

Material and methods


Brightfield images were captured with three different imaging systems: a Z16 Leica lens with a JVC KY-F75U digital camera using Cartograph and Automontage software; an Olympus BX51 compound microscope with a Canon EOS 70D digital SLR camera; and a Leica DM2500 compound microscope with a Leica DFC425 camera. Illumination was achieved with a lighting dome or with LED gooseneck lamps and mylar light dispersers. Images were rendered from Z-stacks with Automontage, Helicon Focus, or Zerene Stacker.

Dissections for scanning electron microscopy were performed with a minuten probe and forceps and body parts were mounted to a 12 mm slotted aluminum mounting stub using a carbon adhesive tab and sputter coated with approximately 70 nm of gold/palladium using Cressington 108 and Denton IV sputter coaters. Micrographs were captured using Hitachi TM3000 Tabletop and Phenom XL G2 Desktop scanning electron microscopes (SEM)

Specimens were analyzed between two #1.5 coverslips with a Nikon A1R-HD Confocal Laser Scanning Microscope (CLSM) at the University of New Hampshire Instrumentation Center using three excitation wavelengths (409, 487, and 560 nm), and three emission ranges of (435–470, 500–540, and 570–645 nm). Pseudo-colors of CLSM micrographs reflect their fluorescence spectra. Media files and volume-rendered micrographs were generated using FIJI (Schindelin et al. 2012).

Material examined

Specimens of the present study (Table 1) were identified using Masner and Huggert (1989), Masner (1980), and Masner (1976). Table 1 contains a list of taxa for which images are available in the figures or can be accessed via the CUID at

Table 1.

Imaging techniques, localities, depositories and family classification for the specimens examined.

Collection Collecting Unit Identifier (CUID) Family/Subfamily Genus/species Imaging method Origin Figure
UNHC FSCA 00000289 Platygastrinae Allostemma sp. Masner & Huggert, 1989 Confocal Laser Scanning LSM USA 19
USNM USNMENT01197966 Platygastrinae Allostemma bicolor Buhl & Choi, 2006 SEM South Korea
USNM USNMENT00872678 Platygastrinae Euxestonotus sp. Fouts, 1925 SEM Nicaragua
USNM USNMENT01109601_1 Platygastrinae Inostemma sp. Haliday, 1833 SEM USA
USNM USNMENT01029164 Platygastrinae Iphitrachelus sp. Halliday, 1835 SEM Dominica 3
USNM USNMENT01109601_4 Platygastrinae Isostasius sp. Förster, 1856 SEM USA
OSUC OSUC 334137 Platygastrinae Isocybus sp. Förster, 1856 brightfield imaging USA 16
OSUC unvouchered Platygastrinae Isocybus sp. Förster, 1856 brightfield photography USA 17
USNM USNMENT00872560 Platygastrinae Leptacis sp. Förster, 1856 SEM Kenya
USNM USNMENT01059861 Platygastrinae Metaclisis sp. Förster, 1856 SEM USA
USNM USNMENT01109899 Platygastrinae Orseta sp. Masner & Huggert, 1989 compound microscope Brazil
USNM USNMENT00872580 Platygastrinae Piestopleura sp. Förster, 1856 SEM Kenya
USNM USNMENT00872803 Platygastrinae Platygaster sp. Latreille, 1809 SEM USA
USNM USNMENT01197981_1 Platygastrinae Sacespalus sp. Kieffer, 1917 SEM SE Asia
USNM USNMENT00872647 Platygastrinae Synopeas sp. Förster, 1856 SEM Kenya
UNHC UNHC_1046722A Platygastrinae Synopeas sp. Förster, 1856 CLSM USA 18
UNHC UNHC_1046722B Platygastrinae Synopeas sp. Förster, 1856 compound microscope USA 5
USNM USNMENT00989620_2 Platygastrinae Trichacis sp. Förster, 1856 SEM USA
UNHC FSCA 00000276 Platygastrinae Trichacis sp. Förster, 1856 CLSM USA 14
CNCI OSUC 334109 Platygastrinae Almargella cristata Masner & Huggert, 1989 brightfield photography Chile
CNCI OSUC 334127 Platygastrinae Rao sp. Masner & Huggert, 1989 brightfield photography Australia
USNM USNMENT00989622_2 Sceliotrachelinae Amitus sp. Haldeman, 1850 SEM USA 1
UCRC UNHC_1046725A Sceliotrachelinae Amitus sp. Haldeman, 1850 CLSM USA 15
UCRC UNHC_1046725B Sceliotrachelinae Amitus sp. Haldeman, 1850 compound microscope USA 6
FSCA OSUC 698061 Sceliotrachelinae SEM Madagascar 4
USNM USNMENT01197842 Sceliotrachelinae Calomerella scutellata Masner & Huggert, 1989 brightfield photography USA
USNM USNMENT01197841 Sceliotrachelinae Errolium sp. Masner & Huggert, 1989 brightfield photography New Zealand
FSCA OSUC 698059 Sceliotrachelinae Fidiobia sp. Ashmead, 1894 SEM Madagascar 2
CNCI USNMENT00989211 Sceliotrachelinae Helava alticola Masner & Huggert, 1989 SEM Colombia
FSCA OSUC 698060 Sceliotrachelinae Isolia sp. Förster, 1878 SEM Madagascar
ANIC ANIC 32 153903 Sceliotrachelinae Oligomerella donnae Masner & Huggert, 1989 brightfield photography Australia
USNM USNMENT01059128 Sceliotrachelinae Parabaeus sp. Kieffer, 1910 SEM Brazil
FSCA OSUC 698062 Sceliotrachelinae Pulchrisolia teras Lahey, 2019 SEM Madagascar
SAMC SAM-HYM-P084755 Sceliotrachelinae Sceliotrachelus karooensis van Noort, 2021 SEM South Africa
USNM USNMENT01197878 Sceliotrachelinae Tetrabaeus sp. Kieffer, 1912 brightfield photography Canada
CNU CNU-HYM-MA-2016107 Sceliotrachelinae compound microscope Myanmar 22
USNM OSUC 226542 Platygastridae Orwellium enigmaticum Johnson, Masner & Musetti, 2009 SEM Chile 7
USNM OSUC 163002 Sparasionidae Archaeoteleia gracilis Masner, 1968 SEM Chile 9
CNU CNU-HYM-MA-2017545 Scelionidae Proteroscelio sp. Brues, 1937 fluorescence microscope Myanmar 12
FSCA DPI_FSCA 00008713 Scelionidae Gryon aetherium Talamas, 2021 CLSM USA 13
CNCI OSUC 148693 Geoscelionidae Huddlestonium exu Polaszek & Johnson, 2007 brightfield photography Ivory Coast
USNM OSUC 264384 Janzenellidae Janzenella innupta Masner & Johnson, 2007 SEM Costa Rica 8
UNHC UNHC_0032469 Janzenellidae Janzenella innupta Masner & Johnson, 2007 CLSM, compound microscope Costa Rica 20–21
SAMC SAM-HYM-P093322 Nixoniidae Nixonia sp. Masner, 1958 brightfield photography South Africa 11
USNM USNMENT01109338 Nixoniidae Nixonia watshami Johnson & Masner, 2006 SEM Botswana
USNM USNMENT00989930 Sparasionidae Sceliomorpha sp. Ashmead, 1893 SEM Costa Rica 10


Morphological terminology follows Mikó et al. (2007), Talamas et al. (2019), and Vilhelmsen et al. (2010) and is aligned to the Hymenoptera Anatomy Ontology (Table 2).

Table 2.

URI Table of morphological terms and annotations in the figures (Seltmann et al. 2012).

abbreviation term HAO definition Figure references URI
ac acetabulum The scrobe that is located anteroventrally on the mesopectus and accommodates the procoxa. 5–6, 13, 17
afp anterior mesofurcal pit The pit that corresponds to the anterior mesofurcal invagination. 3, 7, 14, 16, 22
afi anterior mesofurcal invagination The invagination that arises medioventrally from the mespectus, anterior to the mesofucal pit and is continuous with the invagination of the mesofurca. 6, 15, 17
ats postacetabular sulcus The sulcus that extends posteriorly along the acteabular (epicnemial) carina. 9–10
cx1 fore coxa The coxa that is located on the fore leg. 21–22
cx2 meso coxa The coxa that is located on the mid leg. 5–6
dscr2 mesodiscrimen The discrimen that is located in the mesothorax and corresponds with the mesodiscrimenal lamella. 8–12
dscl2 mesodiscrimenal lamella The discrimenal lamella that is located in the mesothorax. 5–6, 17–18, 20–21, 23A–C
mer mesepimeral ridge The ridge that extends along the posterior margin of the mesopectus. 20
fu2 mesofurca The furca that is not paired, arises from the mesopectus and continuos with the mesodiscrimenal lamella. 19, 23A–F
mesofurcal bridge The apodeme that connects the lateral mesofurcal arms and corresponds to the site of origin of the dorsal mesofurco-profurcal muscle. 23D
mesofurcal invagination The invagination that forms the mesofurca. 23A–F
fup2 mesofurcal pit The furcal pit that is located in the mesothorax. 13–14
mesopectus The sclerite that is U-shaped in cross section, connected anteriorly with the pronotum and the propectus, dorsally with the basalare, the mesonotum, the second axillary sclerite and the subalare, posteriorly with the metapectus and bears the mesodiscrimenal lamella and the mesofurca.
metapectus The area that is located anteriorly of the metapleural carina.
netrion The area that is located posteroventrally on the pronotum and corresponds to the site of origin of the first flexor of the fore wing muscle.
pacp postacetabular pits Paired submedian pits located just posterior to the acetabular carina. 1, 3, 14
vbp ventral bridge of pronotum The area that connects ventrally the left and right halves of the pronotum. 4
posterior mesepimeral area The area that extends along the posterior margin of the mesopleuron and is delimited anteriorly by the mesepimeral sulcus.


In this section, we provide annotated descriptions of morphological traits on the pronotum and mesopectus that have significance in the higher classification of Platygastroidea with special emphasis on Platygastridae. Numbers following each trait description represent characters: states indicated in Table 3.

Table 3.

Mesosomal characters in platygastroid families. 1. netrion: 0 absent, 1 present; 2. pl2-3ax2 origin: 0 from mesopectus, 1 from mesopectus and from pronotum; 3. ventral bridge of pronotum dorsal extension: 0 not extending dorsally, 1:extending dorsally; 4. mesodiscrimen: 0 absent, 1 present 5. mesodiscrimen structure: 0 only posteriorly, 1 present and extending anteriorly to the acetabular carina; 6. mesodiscrimenal lamella anterior end: 0 adjacent anteriorly with the acetabulum, 1 not adjacent anteriorly with the acetabulum; 7. anterior mesofurcal pit: 0 absent, 1 present; 8. anterior mesofurcal pit position: 0 near the middle of the ventral mesopectus, 1 anterior 1/3rd of the ventral mesopectus; 9. setose median pit on acetabulum: 0 absent, 1 present; 10. median invagination of acetabulum: acetabular carina medially enclose a pit-like structure without any distinct invagination: 0 absent, 1 present; 11. mesofurcal bridge: 0 absent, 1:present; 12. postacetabular pits: 0 absent, 1 present, 13. mesepimeral sulcus and the posterior mesepimeral area: 0 absent, 1 present; 14. mesepimeral ridge position: 0 extends along the posterior margin of the mesopectus, 1 extends anterior to the posterior margin of the mesopectus; 15. pl2-3ax3 origin: 0 exclusively from the metapectus, 1 partially from the mesopectus. ? = not observed, na = not applicable.

Family/Characters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Geoscelionidae ? ? 0 ? ? ? 0 na 0 0 ? 0 1 ? ?
Janzenellidae 0 0 0 1 0 1 0 na 0 0 0 0 1 1 1
Neuroscelionidae 0 ? 0 1 1 0 0 na 0 0 1 0 1 1 ?
Nixoniidae 1 1 1 1 1 0 0 na 1 0 1 0 1 1 1
Platygastridae 0 0 0/1 0 na 0/1 0/1 0/1 0 0 0 0/1 0 0 0
Proterosceliopsidae 0 ? 0/1 1 ? ? 0 na 0 0 ? 0 1 ? ?
Scelionidae 1 1 0/1 1 1 0 0 na 0 0/1 1 0 1 1 1
Sparasionidae 1 1 1 1 1 0 0 na 0 0/1 1 0 1 1 1


The netrion is absent (1:0; Figs 1–4) from Platygastridae and Janzenellidae, and the first flexor of the fore wing arises exclusively from the mesopectus (2:0; Fig. 23B, C). The netrion is present (1:1) in Nixoniidae, Scelionidae, and Sparasionidae, and the first flexor of the fore wing arises partially from the pronotum (site of origin of the muscle corresponds to netrion, 2:1; Fig. 23A). The muscle was not observed in other platygastroid families that we examined. The ventral bridge of the pronotum is visible laterally, directly anterior to the ventral mesopectus (3:1; Fig. 4) in some platygastrid genera (Allostemma, Alfredella Masner & Huggert, Amitus, Oligomerella Masner & Huggert, Prototeleia Talamas, Popovici, Shih & Ren), but the first flexor of the fore wing does not partially originate from that area. The ventral bridge of the pronotum is visible laterally in some Proterosceliopsidae but not in other families of Platygastroidea.

Figures 1–4. 

Mesopectus, ventrolateral view 1 Amitus (USNMENT00989622_2) 2 Fidiobia (OSUC 698059) 3 Iphitrachelus (USNMENT01029164) 4 Sceliotrachelinae sp. (OSUC 698061).

The mesodiscrimen is absent from Platygastridae (4:0; Figs 1–4), present only posteriorly in Janzenellidae (5:0; Fig. 8), and present and extending anteriorly to the acetabular carina in other platygastroid families (5:1; Figs 912). The mesodiscrimenal lamella is not adjacent anteriorly to the acetabulum (6:1) in Janzenellidae and Platygastridae (except Synopeas), and in the latter, its anterior-most point is marked by the anterior mesofurcal invagination (Figs 6, 15, 17). The lamella extends anteriorly to the acetabulum (6:2; Fig. 5) in Synopeas (Platygastridae) and the other taxa examined.

Figures 5–6. 

Mesodiscrimenal lamella 5 Synopeas sp. (UNHC_1046722B) 6 Amitus sp. (UNHC_1046725B).

The anterior mesofurcal pit is present (7:1; Figs 1–4, 67, 14–17) in all Platygastridae except Synopeas and is absent (7:0; Figs 813) from other platygastroid families. The pit marks the anterior mesofurcal invagination that is continuous with the invagination of the mesofurca (Figs 15, 17). The anterior mesofurcal pit is located more posteriorly, near the middle of the ventral mesopectus (8:0; Fig. 3), in Sacespalus, Iphitrachelus, and Inostemma, and the pit is in the anterior third of the ventral mesopectus in other Platygastridae (8:1; Figs 1, 2, 4)

Figures 7–10. 

Mesopectus, ventral view 7 Orwellium enigmaticum (OSUC 226542) 8 Janzenella innupta (OSUC 264384) 9 Archaeoteleia gracilis (OSUC 163002) 10 Sceliomorpha (USNMENT00989930).

In Nixoniidae, a setose pit is present on the acetabulum that does not correspond to an invagination and is not connected to the mesofurcal invagination (9:1; Fig. 11). The pit is absent from the other taxa examined (9:0). In Gryon aetherium (Scelionidae), the left and right halves of the acetabular carina medially enclose a pit-like structure without any distinct invagination (10:1; Fig. 13). The medial invagination is absent from other platygastroid families (10:0).

Figures 11–13. 

11 Nixonia (SAM-HYM-P093322), mesopectus, ventral view 12 Proteroscelio (CNU-HYM-MA-2017545), internal mesosoma, lateral view 13 Gryon aetherium (DPI_FSCA 00008713), mesopectus, ventral view.

The mesofurcal bridge is absent (11:0; Figs 18–21, 23E, F) from Platygastridae and Janzenellidae and is present (11:1; Fig. 23D) in other platygastroid families.

Paired, shallow postacetabular pits are present (12:1; Figs 1, 3, 14) in many platygastrid genera (e.g. Amitus, Alfredella, Oligomerella, Fidiobia) and absent from other platygastroid families (12:0; Figs 2, 4).

In Platygastridae, the mesepimeral sulcus and the posterior mesepimeral area are absent (13:0; Figs 1–4), the mesepimeral ridge extends along the posterior margin of the mesopectus (14:0; Figs 19, 20), and the first flexor of the hind wing arises exclusively from the metapectus (15:0; Fig. 23C). In other platygastroid families, the mesepimeral sulcus and posterior mesepimeral area are present (13:1; Fig. 9) and the mesepimeral ridge is anterior and parallel to the posterior margin of the mesopectus (14:1). The first flexor of the hind wing arises partially from the mesopectus in Janzenellidae, Nixoniidae, Scelionidae, and Sparasionidae (15:1; Fig. 23A, B). The muscle was not observed in other families.

Figures 14–17. 

14 Trichacis sp. (FSCA 00000276), ventral view 15 Amitus (UNHC_1046725A) interior of head and mesosoma, lateral view 16 Isocybus (OSUC 334137), mesopectus, ventral view 17 Isocybus (unvouchered), interior of mesopectus, lateral view.

Figures 18–21. 

18 Synopeas sp. (UNHC_1046722A), interior of mesosoma, dorsal view 19 Allostema sp. (FSCA 00000289), internal mesopectus posterior view 20 Janzenella innupta (UNHC_0032469), interior of mesosoma, dorsal view (CLSM) 21 Janzenella innupta (UNHC_0032469), interior of mesosoma, dorsal view (compound microscopy).


The external mesopleuron and metapleuron of Platygastridae are simpler than most other platygastroid families (Masner 1979, 1980; Masner and Huggert 1989), however, this simplicity belies an array of internal characters that are demonstrably informative. Our observations on pectal morphology provide a clear example of this. The proposed synapomorphies have utility for family-level identification and phylogenetic inquiry, which is especially useful for fossil taxa that often exhibit forms quite different from the extant fauna. For example, the anterior mesofurcal pit is recognizable in a specimen from Burmese amber, which contains the oldest representatives of Platygastridae (Fig. 22). This specimen is recognizable as a platygastrid by other characters, but only the ventral aspect is presently visible. This confirms the association of the anterior profurcal pit with Cretaceous Platygastridae and illustrates how this character may be helpful for family-level placement of fossil specimens. Similarly, in a bisected specimen of Proteroscelio Brues, a mesodiscrimen that extends anteriorly to the acetabulum is clearly indicated by a row of foveae (Fig. 12), as in Nixonia and Archaeoteleia. The family-level placement of Proteroscelio is equivocal and may be guided by further examination of its mesosomal morphology.

Figure 22. 

Platygastridae in Burmese amber (CNU-HYM-MA-2016107), habitus, ventral view.

Janzenella was described by Masner and Johnson (2007) with an uncertain position in the superfamily. The genus was later retrieved as sister to Platygastridae in the phylogenetic analysis of Chen et al. (2021). We found that Janzenella is a morphological “missing link” because characters are shared exclusively with Platygastridae while some plesiomorphies associated with the rest of the superfamily are retained (Table 2). The recent study by Bremer et al. (2021) documented characteristics of the pro-, meso- and metafurca in a specimen of Janzenella from Baltic amber, confirming the stability of these characters in Janzenellidae and demonstrating how emerging technologies can be applied to fossil taxa. In the case of Platygastroidea, this line of inquiry is clearly fruitful, as some of the most informative family-level characters are internal skeletomusculature.

Figure 23. 

Illustration of the mesodiscrimenal lamella, invaginations on the ventral mesopectus, sites of origin of first wing flexors (A–C), and configuration of the mesofurca (D–F) A, D Scelionidae, Nixoniidae, Sparasionidae B, E Janzenellidae C, F Platygastridae.

Figure 24. 

Modified phylogeny from Chen et al. (2021) with characters mapped to the topology. Parenthetical numerals indicate the corresponding character: state from Table 3 A mesofurcal bridge present (13:3) B mesepimeral sulcus present (13:1) C first flexor of the fore wing with pronotal site of origin (2:1) D first flexor of the hind wing with mesopectal site of origin (15:1) E discrimenal lamella not extending anteriorly to acetabulum (6:1) F mesofurcal bridge absent (11:0) G first flexor of the fore wing with mesopectal site of origin (2:0) H mesepimeral sulcus absent (13:0) I first flexor of the hind wing with metapectal site of origin (15:0) J anterior mesofurcal pit present (7:1) K discrimenal lamella extending to acetabulum (6:0) L anterior mesofurcal pit absent (7:0).

We suspect that the anterior mesofurcal pit and its corresponding invagination, loss of the mesofurcal bridge, and ancestral wing flexor muscle patterns are interrelated, and that stabilization of the mesofurca shifted to mesofurcal invaginations from the mesofurcal bridge in concert with repositioning of wing flexor muscles. This makes sense considering that the mesofurca serves as the site of origin of numerous muscles involved in flight (e.g. mesofurco-mesolaterophragmal muscle) (Vilhelmsen et al. 2010). We also surmise that the transepisternal line is related to these characters. In Platygastridae, the transepisternal line externally marks the ventral margin of the site of origins of the fore wing flexors (pl2-3ax2a, b) and the retractor of the mesoscutellum (pl2-t2b; Mikó et al. 2007), similar to some Cynipoidea and Diapriidae (Vilhelmsen et al. 2010). Thus, the presence of the transepisternal line might indicate a shift of the first flexor to the mesopectus, given that the line is absent from platygastroids where the first flexor arises from the pronotum (Mikó et al. 2007). The fossil genus Proterosceliopsis Ortega-Blanco, McKellar & Engel (Proterosceliopsidae) offers some additional clues. It has a mesepimeral sulcus, suggesting that the first flexor of the hind wing attaches on the mesopectus. The laterally visible ventral bridge of the pronotum in Proterosceliopsis, termed the netrion in Talamas et al. (2019), is similar to the condition found in Platygastridae (Talamas et al. 2021), leading us to believe that the first flexor of the fore wing arises from the mesopectus in this genus. If this is correct, Proterosceliopsis would have the same configuration of first wing flexor muscles as Janzenella. Platygastridae and Proterosceliopsis are the only platygastroids with a transepisternal line, which further supports the notion that there are mesopectal origins of first flexors of the fore wing in the latter taxon.


Elijah Talamas was supported by the Florida Department of Agriculture and Consumer Services, Division of Plant Industry (FDACS-DPI). We thank Jonathan Bremer (FDACS-DPI) and many participants in the Smithsonian internship program for contributing images. Dong Ren and Chungkun Shih kindly provided a loan of the specimens in Burmese amber from Capital Normal University, Beijing.


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