مالک یا مسافر فرصت‌طلب: بازشناسی جنس Duta Nixon (Hymenoptera: Platygastridae, Scelionidae) در منطقه پالئارکتیک

Introduction

Scelionidae (Hymenoptera: Playgastroidea) is a diverse group of egg-parasitoid wasps, comprising about 4,000 described species belonging to 167 genera (Belokobylskij et al., 2019; Johnson et al., 2019). Members of this family are associated with the eggs of insects from nine orders (Coleoptera, Diptera, Embiidina, Hemiptera, Lepidoptera, Mantodea, Neuroptera, Odonata, Orthoptera), as well as with spiders (Muesebeck, 1979; Austin, 1984; Austin et al., 2005). Higher-level evolutionary relationships within Scelionidae remain unclear (e.g., Austin et al., 2005; Murphy et al., 2007; Taekul et al., 2014; Chen et al., 2021), and the current classification does not accurately reflect the true evolutionary history of the group. In addition, host shift patterns are critical to understanding the evolution of host-finding strategies and the underlying mechanisms driving host selection among these parasitoids (Austin et al., 2005; Murphy et al., 2007; Taekul et al., 2014). The genus Duta Nixon was originally proposed for Holoteleia tenuicornis Dodd, 1920, an Oriental/Afrotropical species (Nixon, 1933). Duta is a relatively small, cosmopolitan genus represented by 29 described species distributed globally (Masner, 1991; Galloway & Austin, 1984; Kozlov & Lê, 2000; Rajmohana, 2007a, 2007b, 2014; Debnath et al., 2026). It is considered a well-defined genus; the concept provided by Masner (1991) in his revision of Nearctic species requires only minor adjustment to accommodate species from other biogeographic regions.

In the Palaearctic region, the genus Duta Nixon currently includes three described species: D. serraticeps (Priesner, 1951), originally described in the genus Chaetanteris Priesner, 1951 from Egypt; D. tenuicornis (Dodd, 1920); and D. dissimilis Rajmohana, 2014, whose type locality is in the Oriental region (Indonesia) and India, respectively. Although D. tenuicornis is originally an Oriental species, multiple records document its occurrence in various parts of the Palaearctic region, including Hungary, Moldova, Greece, and the Russian Far East (Szabó, 1957; Kozlov, 1971; Kononova & Kozlov, 2008). More recently, barcode-supported evidence has indicated the occurrence of D. dissimilis in Russia (Debnath et al., 2026). Around the turn of the millennium, a handful of additional species were described from the Oriental region, including D. indica Mukerjee, 1994, D. tuberculata Rajmohana, 2007, D. typhona Kozlov & Lê, 2000, and D. xyphona Kozlov & Lê, 2000. Despite the addition of several Oriental species in recent decades, a thorough re-examination of these taxa, along with earlier described species, is required to achieve a clearer understanding of species boundaries and classification within this genus. In Iran, 14 scelionid genera and 48 species have been documented (Minab et al., 2023; Ameri et al., 2024; Popovici et al., 2024), representing only a small portion of the country's true diversity. This work provides the first record of the genus Duta from the easternmost border of Iran. The specimens were collected from a xeric habitat dominated by native vegetation such as tamarisk trees and palm groves. In addition, we provide a preliminary world checklist of all described Duta species. This checklist consolidates scattered taxonomic information and offers a comprehensive reference point for future revisionary and phylogenetic studies.

Materials and methods

A series of scelionid specimens was collected from palm groves (Fig. 1A) located in the sub-mountainous terrains of Bandan, South Khorasan Province, Eastern Iran, using Malaise traps (Fig. 1B). Among the collected material, two specimens were identified as belonging to the genus Duta using the identification keys provided by Masner (1976, 1980). The specimens were treated by the AXA protocol (van Achterberg, 2009) and mounted on point-card tips. A Nikon® SMZ-645 stereomicroscope was used for the specimen examination and preparation. Specimens were compared with the original descriptions of previously described species (Priesner, 1951; Masner, 1976; Masner, 1991; Mukerjee, 1994; Kozlov & Lê, 2000; Rajmohana, 2007a, 2007b; 2014), and images made available by Talamas et al. (2017) and Talamas and Pham (2017). Morphological terminology and abbreviations follow Masner (1980) and Mikó et al. (2007). A motorized Auto-focus macrophotography stage (Fast Macro - Omega Optics Co. Ltd., Iran) was used to capture multiple in-depth images. Photographs were taken using a Sony® a7R III camera (Sony Group Corporation, Tokyo, Japan) connected to Mitutoyo® Plan Apo Infinity Corrected Objectives (magnifications 10´ and 50´, Mitutoyo Co., Ltd., Japan), using a 160 mm tubular adaptor (Omega Optics Co., Ltd., Iran). The light source was constructed using Triple LED panels (3 × 20 W, 20 × 20 cm), providing a smooth and diffused light covering all aspects of the specimens. The series of 100–120 partially focused images (depending on the target segment) was selected to be stacked into a single in-focus image. The pyramid approach in Helicon Focus® v. 7 (Helicon Soft Ltd., Kharkiv, Ukraine) was used for image processing of deep stacks, increasing contrast and reducing glare. Abbreviations used in the text are as follows: A1–A12 = antennomeres 1–12; T1–T7 = gasteral tergites 1–7; H = height; W = width. Examined specimens are deposited in the collection of the Department of Plant Protection, University of Zabol, Zabol, Iran (DPPZ).

Results

Taxonomy

Class Insecta Linnaeus, 1758

Order Hymenoptera Linnaeus, 1758

Superfamily Platygastroidea Haliday, 1833

Family Scelionidae Haliday, 1839

Subfamily Scelioninae Haliday, 1839

Genus Duta Nixon, 1933

Type species. Holoteleia tenuicornis Dodd, 1920, by monotypy and original designation.

Type information. Holotype female, NHMUK. Country of type locality: Indonesia.

Diagnosis. Antenna with 12 antennomeres in both sexes; clava clearly distinguished in females, usually with 6 clavomeres, A3–A5 often distinctly elongate and subequal in length in females; male antenna filiform; eyes large, setose, rounded and hairy; head globular; Gena and frons without any trace of radiating striae, frontal depression never developed; occipital carina distinct; skaphion well developed; notauli variable; netrion distinct; metascutellum present as a smooth strip, not produced posteriorly marginalis either elongate or shorter to almost point-like, postmarginalis well developed, basalis sometimes spurious.

Fig. 1. The sampling locality of Duta bicolor Rajmohana, 2014. A. The Palm Grove in Bandan county, Southern Khorasan province; B. The installed Malaise trap in eastern Iran.

Subcosta with erect bristles all along its length, wings sometimes shortened; metasoma elongate, spindle-shaped, T1 at most with indistinct bulge or perfectly flat, T7 in females retracted, attached to ovipositor when extruded.

Host. Presumed to parasitise the eggs of various ground crickets (Orthoptera: Grylloidea, Gryllidae, Nemobiinae) (Masner, 1991).

Molecular data. To date, a total of 153 nucleotide sequences representing four genes (18S, 28S, COI, and wg) have been reported for Duta specimens in public databases, including NCBI (https://www.ncbi.nlm.nih.gov) and BOLD (https://boldsystems.org).

Duta bicolor Rajmohana, 2014 (Figs 2A–C, 3A–F)

Duta bicolor Rajmohana, 2014:79, Holotype ♀ (ZSI).–INDIA.

Material examined. 2 ♀♀ (Fig. 3A), IRAN, South Khorasan province, Bandan (31°23'42"N, 60°43'01"E, 737.46 m), 12- VI-2021; F. Minab, leg.

Comparative material examined. Holotype [images], Chaetanteris serraticeps, Female, Meadi, Egypt, 06-XI-33 D, Dr. H. Priesner; H. Priesner’s Collection, 1968; Type No. 70869, USNM. Refer to: https://mbd-db.osu.edu/hol/ collecting_units/0eae5d0b-a5f1-3aaa-e053-0100007f2cc9; Holotype [images], Duta bicolor, Female, India, Kerala, Madakkimala, 09-I-2009, Dr. K. Rajmohana; ZSI/ WGRS/PF23.

Note: The morphological traits of the recently collected specimens align closely with the original description (Rajmohana, 2014), except for a slightly darker body coloration and lighter pigmentation of the eyes; less pilosity of the face below the anterior oceli; shorter T1 (0.5–0.5 vis 0.8 in the Indian specimens), and more erect black bristles on submarginal vein (12–14 vis 11 in the Indian specimens). Episternal foveae are observed as very small, shallow depressions on the anterior part of the mesopleuron; however, their presence or absence was not mentioned in the original description of D. bicolor. Debnath et al. (2026) interpreted the episternal foveae as absent in the holotype of D. bicolor, whereas the Iranian specimens possess minute shallow depressions; nevertheless, their identification is supported by the overall morphology, particularly the distinctly elongate marginal vein.

Diagnosis. Duta bicolor is closely related to D. serraticeps (Priensner, 1951) in the Palaearctic region, from which it can be separated by the serrations on the gena, which are only found in D. serraticeps [but also in Neoduta serrata Rajmohana & Patra, 2012], by the following characters: The robust micro-sculpture on the vertex extended beyond the anterior ocelli in D. serraticeps, while the fine microsculptures truncated before the posterior ocelli in D. bicolor. The occipital area, vertex, and lateral part of frons with relatively dense setae in D. serraticeps, while these areas are sparsely setose in D. bicolor. The lateral lobes of the propodeum are positioned apart at the site of the median lobe of the metanotum in D. serraticeps, whereas these lobes are closer together in D. bicolor. Additionally, these two species have different colour patterns. Duta serraticeps has a body with dark brown colouration, except the reddish brown T1 and yellowish legs, while D. bicolor is distinctly bicolorous; its head and tip of abdomen are shiny black, and the rest of the body, except T1 and legs (yellow), are brown. Furthermore, the antennae are generally brown in D. serraticeps, with it being bicolorous in D. bicolor. The radicle and basal half of the scape are yellowish brown, and the rest run to blackish brown.

Redescription. Body length 1.2 mm (without ovipositor), wing length 1.0 mm.

Colouration (Fig. 2A–B). Head Black; eyes silvery and ocelli black; mandibles brownish yellow; funiculars and clava contrasting in colour with scape, pedicellus and radicle; radicle, and base of A1 yellow; upper half of A1 brownish yellow; A2–A12 dark brown to black; legs including coxae bright yellow; T1–T3 yellowish brown; T4–T6 dark brown; wings slightly infuscated.

Head. Transverse in dorsal view (Fig. 3C), sub-circular in frontal view, its width nearly twice its length, with very few scattered setae (Fig. 3A, 3C); frons smooth and shiny; gena sparsely setose; temple with few sparse setae (Fig. 2A); occiput emarginate (Fig. 3C), occipital carina finely but distinctly crenulate; occiput and vertex roughly coriaceous, coriaceous sculpture continuing along inner orbits, attenuating below anterior ocellus; compound eye large (Fig. 3A), distinctly setose; inner orbital margins diverging ventrally; malar sulcus deep, slightly widened in anterior (or ventral) half; mandible tridentate, teeth roughly equal in size; antennae (Fig. 3B) covered with fine pilosity; clava abrupt, 6-merous and transverse; scape and pedicel cylindrical and elongated; pedicel longer than A3; maximum width of the clavomeres is twice the width of the funiculars.

Mesosoma. Longer than wide (L/W:1.81; Indian specimen: 1.51), in dorsal view (Figs 2B, 3D); its width including tegulae subequal to width of head; mesoscutum and mesoscutellum with sparse, long setae; notaulus deep and broad, internotaular distance at anterior margin nearly 1.6 times distance at posterior margin; scutoscutellar sulcus deep medially, laterally with three large foveae; mesoscutellar disc with long, scattered, semidecumbent setae, smooth and polished except for few setigerous punctures in anterior half; posterior mesoscutellar sulcus foveate; metascutellum narrow; lateral propodeal area mostly smooth, with foveae along anterior and posteromedian margins; lateral propodeal carinae not continuous medially (Fig. 3E); metasomal depression smooth; mesosoma in lateral view (Fig. 2A) slightly longer than high, dorsally convex; lateral pronotum predominantly smooth and glabrous, with pronotal shoulder not distinctly foveolate; netrion foveolate along anterior margin, foveolae smaller than half of netrion width, gradually diminishing dorsally; femoral depression smooth and glabrous; mesopleural carina complete, sharp, without foveolae ventrally; episternal foveae and mesepisternal sulcus present, as shallow depressions; metapleuron smooth and glabrous; paracoxal sulcus indicated by minute foveolae along anterior margin; metapleural sulcus indicated by a smooth furrow; fore wings (Fig. 3F) long and relatively narrow, exceeding the tip of metasoma; with 12–14 erect black bristles on submarginal vein; marginal vein 4 times longer than stigmal vein; postmarginal vein markedly elongate, approximately four  times longer than the stigmal vein, stigmal vein oblique and knobbedbasal vein indicated as nebulous trace.

Metasoma. Excluding partially extended ovipositor system, metasoma, 1.85 times combined length of head and mesosoma (Fig. 2A–B); metasoma in dorsal view (Fig. 2A) 3.1 times longer than wide; T1 (Fig. 3E) 1.86 times wider than long, with strong longitudinal costae, with lateral setae; T2 to T6 transverse; T2 1.83 times wider than long, with strong longitudinal costae in anterior three-quarters, remainder of tergite smooth with scattered setae laterally; T3 2.0 times longer than T2, smooth and glossy, and with scattered, semidecumbent setae posterolaterally; T3 1.35 times longer than T4–T6 combined, with white short and sparse setae; T4–T6 smooth with decumbent setation laterally; T7 exserted along with ovipositor; three bristles on cercus (Fig. 2A).

Fig. 2. Duta bicolor Rajmohana, 2014, female. A. Habitus, lateral view, B. Habitus, dorsal view (Head, mesoscutum, mesoscutellum, propodeum, TI, metasoma, ovipositor); C. The whole body, dorsal view; D. Second specimen with an extended ovipositor.

Male. Not yet collected in the Palaearctic region. The original description (Rajmohana,  2014 – fig. 69) illustrates the male antenna. However, all paratypes are female, and there is no accompanying description for the male specimens.

Biology. Unknown.

Distribution. Oriental (India), Palaearctic (Iran).

Fig. 3. Duta bicolor Rajmohana, 2014, female. A. Head, frontal view; B. Antenna; C. Head, dorsal view; D. Mesosoma, dorsal view; E. Propodeum, T1 and T2, dorsal view; F. Fore and hind wings.

Discussion

So far, no species of the genus Duta has been recorded from Central and Western Asia. It is mainly distributed in different biogeographic regions of the world, including the Afrotropical (Nixon, 1933), Australasian (Galloway & Austin, 1984), Nearctic (Masner, 1964, 1991), Oriental (Rajmohana, 2007a, 2014), and western Palaearctic (Priesner, 1951; Szabó, 1957; Kozlov, 1971; Kononova & Kozlov, 2008). The checklist presented in Table 1 herein compiles available information on all described species of Duta before Debnath et al. (2026), without re-examination of type or additional specimens (Ashmead, 1893; Dodd, 1913, 1914, 1920; Galloway & Szabó, 1966; Austin, 1983; Masner, 1991; Mukerjee, 1994; Kozlov & Lê, 2000; Rajmohana, 2007a, 2007b, 2014).  During the production of the present paper, Debnath et al. (2026) published descriptions of ten additional Indian species of Duta, with the type material deposited in ZSIK: D. coriata, D. foveola, D. microphleba, D. obscura, D. pallida, D. procera, D. protuberata, D. semiannulata, D. succina, and D. xantha. A thorough revision of the genus is needed, not only for Duta itself, but also for closely related genera, to resolve longstanding ambiguities.  Duta bicolor is a newly recorded addition to the scelionid fauna of Iran; its discovery represents the third Duta species in the Palaearctic region (Priesner, 1951). This species was collected from a desert habitat in the Bandan region, southeast of South Khorasan province. Given the diversity of this genus in the Oriental region (Mukerjee, 1994; Rajmohana, 2007a, 2007b, 2014), it is reasonable to expect the presence of additional species in the southeastern areas of the country. The occurrence of the species with an Oriental origin in various regions of Iran, particularly in the south and southeastern borders, indicates a biogeographical connection, which has been previously documented for many other groups of Hymenoptera (Rahmani et al., 2019; Rosa et al., 2024).

Furthermore, records for the existence of the elements from the Afrotropical (Derafshan et al., 2021; Rosa et al., 2024) in the same area of Iran also suggest a convergence of three biogeographical realms. This connection is largely a result of a shared geological history or the expansion in the distribution of the opportunistic or Hitchhiking species over a long-time scale (Noori et al., 2024). No clear host evidence has been recorded for Duta species, other than a report by Masner (1991) that gryllids (Grylloidea) are the hosts. Gryllids are active across a wide range of habitats, and most species deposit their eggs either in or on plant tissues, where clutches may be sought by parasitoids (Masner, 1976, 1991). In general, the egg parasitoids employ different dispersal strategies compared to other parasitoids that target mobile stages of their hosts (larvae, nymphs, and adults). A key behavior is the attachment to the body of the female host insect (phoresy) prior to oviposition (Rajmohana & Patra, 2023). In the case of gryllids, as potential hosts of Duta species (Masner, 1991), this makes it difficult to consider this as a factor for dispersal across two biogeographical realms. However, it can be hypothesized that the oviposition habit of female gryllids - where they lay eggs in plant tissues (Naskrecki, 2001) - combined with human-mediated transfer of plant materials, may contribute to the transmission and expansion of the distribution range of this group of egg parasitoids.  Considering the rich diversity of the parasitic hymenoptera in the south and southeastern parts of Iran (e.g., Ghafouri Moghaddam et al., 2018; Rahmani et al., 2019; Minab et al., 2023; Ameri et al., 2024), it is likely that there are undiscovered species of the genus Duta throughout various regions of the country. It is more likely to be found in scattered populations across the northeastern regions of the country, as well as in areas bordering Pakistan, Afghanistan, and Turkmenistan. Further research on host relationships and their role in natural biological control is also essential.

Author's Contributions

Farzad Minab: Field survey, collection, preparation and photography of the specimens, taxonomic identification, and drafting the manuscript; Ehsan Rakhshani: Supervising, methodology, review and editing; Elijah J. Talamas: Taxonomic identification, photography of the comparative material, review and editing; Mostafa Ghafouri-Moghaddam: drafting, review and editing.

Author's Information

Funding

This research received no specific grant from any funding agencies.

Data Availability Statement

All data generated or analyzed during this study, including detailed methodology, are available from the corresponding author upon reasonable request.

Acknowledgments

This article forms a part of the PhD thesis of the first author and has been prepared and submitted in partial fulfillment of the requirements for the doctoral degree. Elijah Talamas was supported by the Florida Department of Agriculture and Consumer Services, Division of Plant Industry.

Ethics Approval and Consent to Participate

Insects were used in this study. All applicable international, national, and institutional guidelines for the care and use of animals were followed. This article does not contain any studies with human participants performed by the authors.

Conflict of Interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

Generative AI statement

The authors declare that no Gen AI was used in the creation of this manuscript.