﻿The ectoparasitoid wasp Heterospilussicanus (Marshall, 1888) (Hymenoptera, Braconidae, Doryctinae) as a natural enemy of Gastralluspubens Fairmaire, 1875 (Coleoptera, Ptinidae) in Italy

﻿Abstract Heterospilussicanus (Marshall, 1888) is redescribed and illustrated based on the holotype of Dendrosotersicanus Marshall, 1888 and on recently collected material from its type locality (Sicily, Italy). Previous host records for this species are unreliable. Here, the host of H.sicanus, the rare ptinid beetle Gastralluspubens Fairmaire, 1875, is recorded for the first time, having been reared in a historic library in Palermo, Italy. Heterospilussicanus is compared with the similar species Telebolus (= Heterospilus) corsicus Marshall, 1888, which was described in the same monograph from Corsica (France), and it is also redescribed and illustrated. Atoreuteusceballosi Docavo Alberti, 1960, syn. nov. is synonymised under Heterospilussicanus (Marshall, 1888), and Hormiopterus (= Rhaconotus) ollivieri Giraud var. flava Fahringer, 1931, syn. nov. is a junior synonym of Heterospiluscephi Rohwer, 1925. A key for determination of the Western Palaearctic Heterospilus species with a striate vertex is provided and the distributions of H.sicanus and H.corsicus are discussed.


Introduction
The family Braconidae is a vast group within the order Hymenoptera, comprising more than 20,000 recognised species (Yu et al. 2016).Together with the family Ichneumonidae it constitutes one of two recent families of Ichneumonoidea, the vast majority of which are parasitoids (Wharton 1993).
The braconid subfamily Doryctinae is renowned for its exceptional genera and species richness and diversity, including more than 2000 described species distributed globally across almost 200 genera (Shenefelt and Marsh 1976;Marsh 1993Marsh , 2002;;Belokobylskij et al. 2004aBelokobylskij et al. , 2004b;;Belokobylskij and Maetô 2009;Yu et al. 2016).Doryctines, for the most part, are idiobiont ectoparasitoids on the larvae of xylophagous and bark-boring Coleoptera.Some members of this group also parasitise the larvae of Lepidoptera and Hymenoptera (Symphyta), while a few genera are known to be phytophagous (Ramírez and Marsh 1996;Wharton and Hanson 2005;Zaldívar-Riverón et al. 2007, 2014).Additionally, in certain cases, they function as parasitoids (perhaps endoparasitoids) of adult Embioptera or have been observed inhabiting termite nests (Shaw and Edgerly 1985;Wharton 1993;Kistner et al. 2000;Belokobylskij 2002).
Within this subfamily, the genus Heterospilus Haliday, 1836, belonging to the tribe Heterospilini, stands out as one of the largest and most hyperdiverse braconid genera, with already more than 400 species described and many more to be described (Marsh et al. 2013;Yu et al. 2016;Ghahari et al. 2022).In total, 21 species of Heterospilus of 45 Palaearctic species are known in Europe, while more than 340 species have been described from the New World (Nearctic and mainly Neotropics) and 37 species from the Oriental region; only one species has been described from Australia and none from the Afrotropical region (Yu et al. 2016;Belokobylskij and Ku 2021).
In this study we provide an illustrated redescription and updated diagnosis of Heterospilus sicanus (Marshall, 1888), discovered in the frass, holes, and tunnels created by Gastrallus pubens Fairmaire, 1875 (Coleoptera: Ptinidae) in books seriously infested by this book-boring beetle during inspections in the "Ottavio Ziino" Law History Library of the Law Department at the University of Palermo (Sicily, Italy).Heterospilus sicanus is compared with the congeneric Telebolus (= Heterospilus) corsicus Marshall, 1888, which is also redescribed and illustrated, and Atoreuteus ceballosi Docavo Alberti, 1960 is here synonymised under H. sicanus (Marshall, 1888).Finally, a key for the determination of the Western Palaearctic Heterospilus species with a striate vertex is included and the distributions of H. sicanus and H. corsicus are discussed.

Materials and methods
The terminology employed in this work for the morphological features, measurements, and wing venation nomenclature follows Belokobylskij and Maeto (2009), with the terminology for wing venation by van Achterberg (1993) shown in parentheses.Images were taken using a Leica DM series compound microscope (Leica, Benzheim, Germany) and a Leica DFC series mounted camera with Leica Application Suite software (LAS EZ 3.4.0,Leica, Switzerland), and with a Canon SLR EOS 5DSR with either a 65 mm macro lens or a Mitutoyo 10× lens in combination with a 70-130 mm macro lens, mounted on a stand with an automated Z-stepper (the Natural History Museum, London, UK).All insect photos were integrated using the freeware CombineZP (Hadley 2011) or Helicon Focus and processed in Adobe Photoshop CS4.

Abbreviations of specimen depositories
The specimens (including types) examined in this study have been deposited in the following collections.The original description of Dendrosoter sicanus Marshall, 1888: 242, translated from French, is as follows: "Head transverse, largely dark brown as well as the thorax; the rest of the body tawny; abdomen black towards the tip.Vertex high, gibbous, without frontal protuberances, finely wrinkled crosswise; eye and stemmaticum smooth.Ocelli sunk in the head, the front one placed on the slope of the forehead.Frontal excavation very shallow and poorly determined.Orbits and genae fawn.Antennae as long as the body, slender, blackish with ferruginous base, with 20 antennal segments.Thorax granular, slightly shiny.Mesonotum dark brown; its crenulated furrows converging towards a deep, rough dimple.Metanotum fawn, slightly shiny, granular irregularly streaked lengthwise on its anterior part, roughly reticulated in rear, with several high lines which cross in all directions.Wings slightly smoky, veins and stigma brown; second cubital cell receiving the recurrent vein; vein posterior non-interstitial.Legs fairly short and thick, testaceous.Abdomen as long as the head and thorax, and wider than the latter, tawny, becoming more and more blackish towards the end, last segment pale; first segment in truncated triangle, twice wider at the tip than at the base, bicarinated and high in the middle, depressed on the side edges, leathery, dull, longitudinally streaked.Second suture erased, even on the sides.Second segment very linearly wrinkled at the base, smooth and shiny on the rest of its surface, as well as all the following ones.Ovipositor as long as the abdomen.Male unknown.Long.2-3.5 mm." Marshall (1897: 127) additionally noted (here translated from French), "This species [D.sicanus], like the others, is variable as to the size and the colours.I received from Genoa two ♀ which are much darker than the type, and one of which is only half the size indicated.In other aspects their features agree with those of D. sicanus.Homeland: add, Italy (Genoa), sent from Mr Mantero." Mantero (1904: 28) elaborated on the Italian specimens (here translated from Italian): "Belvedere, July 1891 (Solari).The Ligurian specimens, also cited by Marshall (1897) have a darker colour than the type."
Head.Head not depressed, its width 1.6× median length, 1.1× width of mesoscutum.Head behind eyes weakly convex anteriorly, evenly and roundly narrowed posteriorly.Transverse diameter of eye 1.2× longer than temple (dorsal view).Ocelli small, in almost equilateral triangle.POL 1.3× Od, 0.35× OOL.Diameter of antennal socket equal to distance between sockets, twice distance between socket and eye.Eye with sparse and short setae, without emargination opposite antennal sockets, 1.2× as high as broad.Malar space 0.7× height of eye, 1.2× basal width of mandible.Face convex, its width 1.2× height of eye and almost equal to height of face and clypeus combined.Malar suture absent.Clypeus with distinct lower flange.[Hypoclypeal depression covered by glue.]Occipital carina complete dorsally, ventrally joining hypostomal carina distant from base of mandible.Head below eyes (front view) roundly narrowed.Hypostomal flange distinct but narrow.Antennae.Antenna slender, filiform, 20-segmented, almost as long as body.Scape rather short and thick, 1.5× longer than its maximum width.First flagellar segment slender, almost straight, subcylindrical, 5.5× longer than apical width, almost as long as second segment.Penultimate segment 3.3× longer than wide, 0.6× as long as first segment, 0.9× as long as apical segment; the latter pointed apically and without spine.
Metasoma.Metasoma 0.9× as long as head and mesosoma combined, 1.8× longer than its maximum width.First segment with short acrosternite.First tergite with not high but rather distinct and wide median area, with distinct dorsope, without spiracular tubercles; tergite distinctly and almost linearly widened from base to apex.Length of first tergite equal to its apical width, 1.4× length of propodeum; maximum width of tergite ~ 2.0× its minimum width.Median length of second tergite 0.45× its basal width, 0.8× length of third tergite.Combined length of second and third tergites 0.9× basal width of second tergite, 0.7× their maximum width.Second suture present, but fine, usually weakly curved laterally.Third tergite without transverse furrow.Ovipositor sheath rather slender, 0.8× as long as metasoma, 1.1× longer than mesosoma, 0.4× as long as body, 0.5× as long as fore wing.
Sculpture and pubescence.Vertex entirely distinctly and rather densely transversely striate, partly with very fine additional reticulation between striae; frons entirely densely and distinctly transversely striate [face covered in glue]; temple smooth.Mesoscutum densely and distinctly granulate, medioposteriorly with two posteriorly convergent carinae.Scutellum granulate.Mesopleuron entirely rugose-striate.Metapleuron entirely distinctly rugose-reticulate.Propodeum with rather wide, short and finely granulate-coriaceous basolateral areas, weakly delineated by carinae; areola finely delineated; basal carina 0.8× as long as anterior fork of areola; posterior 0.7 of propodeum irregularly rugose-reticulate.Hind coxa densely granulate, transversely striate dorsally.Hind femur finely and densely granulate-coriaceous. First tergite with rather distinct and posteriorly convergent dorsal carinae, densely and distinctly longitudinally striate, with fine and dense additional reticulation between striae.Second tergite mostly distinctly longitudinally striate, laterally smooth over rather wide area, rugulose postero-medially.Remaining tergites smooth.Vertex almost entirely with rather dense, short and semi-erect setae arranged in rows.Mesoscutum with rather dense, relatively long and semi-erect pale setae at wide area along notauli and scattered across lobes, all lobes narrowly glabrous medially.Hind tibia dorsally with short, sparse, semi-erect setae; length of these setae ~ 0.3× maximum width of hind tibia.
Colour.Body reddish brown, vertex, mesonotum, and posterior half of metasoma dark reddish brown.Antenna dark brown, four basal segments pale brown.Palpi yellow.Legs entirely pale brown.Ovipositor sheath mainly brown, black apically.Fore wing very faintly infuscate.Pterostigma almost entirely brown.
Male.Body length 2.6-2.8mm; fore wing length 2.1 mm.Antennae slender, filiform, 21-segmented, approximately as long as body.Hind wing with relatively small, complex, brown stigma-like enlargement, its length 0.7-0.8×distance from base of wing to base of enlargement.Length of first metasomal tergite 1.1× its apical width.Second tergite entirely striate.Median length of second tergite 0.75× its anterior width, 1.2× length of third tergite.Third tergite with shallow and crenulate transverse furrow in anterior one-third.Body mainly brown to dark brown, anterior third of metasoma paler.Otherwise similar to female.
Distribution.According to Taxapad, the world catalogue of Ichneumonoidea (Yu et al. 2016), besides Italy (Sicily), H. sicanus has also been recorded in Spain (Falco Gari et al. 1993), Croatia (Papp 1977), Serbia (Brajkovic 1989), and Hungary (Papp 1984); however, at least some of these records require confirmation.In Russia, this species has only been found in Crimea (new record; see 'Additional material examined'), whereas its records from the North Caucasus of Russia (Tobias 1971(Tobias , 1976) ) were erroneous (for details see 'Remarks' under the 'Hosts' section).
Western Palaearctic Heterospilus species with an almost entirely sculptured vertex can be differentiated using the key below.Head.Head not depressed, its width 1.5× median length, 1.3× width of mesoscutum.Head behind eyes evenly and roundly narrowed.Transverse diameter of eye 1.6× longer than temple (dorsal view).Ocelli small, in almost equilateral triangle.POL almost equal to Od, 0.4× OOL.Diameter of antennal socket 1.3× distance between sockets, 1.8× distance between socket and eye.Eye without setae, with shallow emargination opposite antennal sockets, 1.2× as high as broad.Malar space 0.5× height of eye, 1.3× basal width of mandible.Face convex, its width 1.15× height of eye and 1.3× height of face and clypeus combined.Malar suture absent.Clypeus with short lower flange.Hypoclypeal depression rather small and suboval, its width 0.7× distance from edge of depression to eye, 0.35× width of face.Occipital carina complete dorsally, joining hypostomal carina ventrally distant from upper base of mandible.Head below eyes distinctly and weakly-roundly narrowed.Hypostomal flange distinct but narrow.
Antenna.Antenna weakly thickened, filiform, 21-segmented, slightly longer than body.Scape rather long and thick, 1.5× longer than its maximum width.First flagellar segment weakly thickened, weakly curved, subcylindrical, 4.5× longer than its apical width, almost as long as second segment.Penultimate segment 2.7× longer than wide, 0.6× as long as first segment, 0.9× as long as apical segment; the latter pointed apically and without spine.
Mesosoma.Mesosoma not depressed, its length 1.8× maximum height.Pronotal neck rather long, dorsally weakly convex, but without convex lobe and pronotal carina; side of pronotum with rather shallow, weakly curved and wide submedian oblique and sparsely crenulate furrow.Mesoscutum highly and roundly elevated above pronotum (lateral view), maximum width of mesoscutum 1.3× its length (dorsal view).Median lobe of mesoscutum (dorsal view) weakly protruding forwards, without anterolateral corners, distinctly convex anteriorly.Notauli rather narrow, deep, sparsely and finely crenulate.Prescutellar depression deep, long, with median carina, finely and irregularly sculptured, 0.5× as long as wide, 0.55× as long as scutellum.Scutellum convex, with fine lateral carinae, its basal width almost equal to median length.Subalar depression rather deep, wide, sparsely and coarsely striate.Precoxal sulcus rather deep, almost straight, distinctly crenulate, running along anterior 0.6 of lower part of mesopleuron.Metanotal tooth (lateral view) rather long, wide, more or less pointed apically.Metapleural lobe rather long, more or less wide, rounded apically.Propodeum (lateral view) regularly convex-roundly slanted from base to apex, without lateral tubercles; propodeal spiracle small.
Metasoma.Metasoma 0.9× as long as head and mesosoma combined, almost twice as long as its maximum width.First tergite with rather high and wide median area, with small dorsope, without spiracular tubercles; tergite strongly and almost linearly widened from anterior to posterior apex.Length of first tergite 0.85× its apical width, a little larger than length of propodeum; maximum width of tergite 2.5× its minimum width.Median length of second tergite 0.4× basal width of second tergite, 0.7× length of third tergite.Combined length of second and third tergites 0.9× basal width of second tergite, 0.7× their maximum width.Second suture distinct, distinctly curved laterally.Third tergite without sculptured transverse furrow.Ovipositor sheaths 0.8× as long as metasoma, 1.1× longer than mesosoma, 0.4× as long as body, 0.6× as long as fore wing.

Figure 1 .
Figure 1.Heterospilus sicanus (Marshall, 1888) (female, holotype) A habitus, dorsal view B habitus, lateral view C head, mesosoma and base of metasoma, lateral view D head, mesosoma and base of metasoma, dorsal view E propodeum, metasoma and ovipositor, dorsal view F head and mesoscutum, dorsal view G wings H labels.

Figure 3 .
Figure 3. Heterospilus sicanus (Marshall, 1888) (female) A mesosoma, ventro-lateral view B fore wing C hind wing D fore leg (white arrows indicate short stout spines on its front tibia surface and black arrow those on the apical part) E middle leg F hind leg (black arrow indicates a distinct antero-ventral basal tubercle on the coxa) G metasoma, dorsal view H first tergite, dorso-lateral view I ovipositor and one of its sheaths J ovipositor apex.

Figure 4 .
Figure 4. Heterospilus sicanus (Marshall, 1888) (male) A habitus, lateral view B head, front view C head, lateral view D head dorso-lateral view E head dorsal view F labial palpus G maxillary palpus H antenna I mesosoma, dorsal view J pronotum, antero-dorsal view K mesosoma, lateral view.