Mesopolobus robiniae Lakatos & László, 2021

László, Zoltán, Lakatos, K. Tímea & Dénes, Avar-Lehel, 2021, A new species of Mesopolobus (Hymenoptera, Pteromalidae) from black locust crops, European Journal of Taxonomy 740 (1), pp. 118-137 : 128-133

Mesopolobus robiniae Lakatos & László sp. nov.

urn:lsid:zoobank.org:act:9650B871-3BF8-49C8-9329-43A67A3C2D5B

Fig. 5

Diagnosis

Mesopolobus robiniae sp. nov. is characterized by having the following morphological characters: head with uniform reticulation, antennae inserted at or above ventral edge of compound eyes, with three anelli, head broader than mesoscutum, pronotal collar moderately long, marginal vein of fore wing about twice as long as the stigma vein, metasoma longer than mesosoma, with only slightly projecting ovipositor sheaths, body green, antennae proximally testaceous with funiculus and clava infuscate, femora and tibiae testaceous, with hyaline wings. Mesopolobus robiniae sp. nov. differs from closely resembling species by the ratios of metasoma to head plus mesosoma length, of temples to eye length, of marginal to stigma vein, of pronotal collar to mesoscutum length and of antennal clava to head length. Molecular results: the three sequenced individuals represented one haplotype (GenBank accession number: MF098549 ); based on the BI tree the new species, shows a well-supported differentiation from M. verditer as the closest species and from other congenerics with the maximal differentiation from M. tibialis .

Etymology

The new Mesopolobus species is named after the host plant of its seed predator host, the black locust ( Robinia pseudoacacia ).

Material examined

Holotype

ROMANIA • ♀; Bihor County, near Săldăbagiu de Munte; 47.096354° N, 21.984963° E; 11 Mar. 2015; T.K. Lakatos leg.; emerged on 1 Apr. 2015; MZBBU HYM000011 .

Paratypes

ROMANIA – Bihor County • 1 ♂; same collection data as for holotype; MZBBU HYM000012 • 1 ♀; near Săldăbagiu de Munte; 47.100895° N, 21.967509° E; 8 Mar. 2014; T.K. Lakatos leg., emerged on 22 Apr. 2014; MZBBU HYM000017 • 1 ♀; near Săldăbagiu de Munte; 47.098182° N, 21.975352° E; 11 Mar. 2014; T.K. Lakatos leg.; emerged on 23 Apr. 2014; MZBBU HYM000018 • 2 ♂♂; near Săldăbagiu de Munte; 47.098182° N, 21.975352° E; 8 Mar. 2014; T.K. Lakatos leg.; emerged on 22 Apr. 2014; MZBBU HYM000019 , HYM000020 • 1 ♂; near Săldăbagiu de Munte; 47.079446° N, 21.970817° E; 14 Mar. 2009; T.K. Lakatos leg.; emerged on May 2009; MZBBU HYM000021 • 1 ♂; near Săldăbagiu de Munte; 47.098519° N, 21.984808° E; 11 Mar. 2015; T.K. Lakatos leg., emerged on Apr. 2015; MZBBU HYM000022 . – Cluj County • 1 ♀; near Cluj-Napoca; 46.777109° N, 23.674495° E; 17 Mar. 2015; T.K. Lakatos leg.; emerged on 10 Apr 2015; MZBBU HYM000013 • 1 ♀; same collection data as for preceding; 18 Mar. 2014; T.K. Lakatos leg.; emerged in May 2014; MZBBU HYM000014 • 2 ♀♀; near Cluj-Napoca; 46.768086° N, 23.568935° E; 17 Mar. 2009; T.K. Lakatos leg.; emerged in Apr. 2009, MZBBU HYM000015 , HYM000016 • 1 ♂; near Cluj-Napoca; 46.834976° N, 23.651004° E; 22 Mar. 2014; T.K. Lakatos leg.; emerged in May 2014; MZBBU HYM000024 • 1 ♂; near Cluj-Napoca; 46.768086° N, 23.568935° E; 17 Mar. 2009; T.K. Lakatos leg.; emerged in May 2009; MZBBU HYM000025 .

HUNGARY • 1 ♂; Hajdú-Bihar County, near Debrecen; 47.554773°N 21.591610°E; 2 Mar. 2015; T.K. Lakatos leg.; emerged on Apr. 2015; MZBBU HYM000023

Other material (specimens used for the genetic analysis)

ROMANIA • 3 ♀♀; Bihor County, near Săldăbagiu de Munte; 47.0968° N, 21.98525° E; 13 Mar. 2014; T.K. Lakatos leg.; emerged on 17 Apr. 2014; GenBank accession number: MF098549 . This specimens were fully processed for the DNA extraction .

Description

Female

LENGTH. 2.05 to 3.00 mm (N = 15, mean = 2.6, sd = 0.29 mm).

COLORATION. Body green, sometimes with golden reflections; metasoma bronze-black distally, some of the tergites occasionally with blue or violet flecks. Coloration of antennae: scape, pedicellus and anelli testaceous, sometimes last anellus infuscate, all funicular segments and clava infuscate, occasionally brown. Coxae concolorous with the mesosoma, femora and tibiae testaceous, the tips of the fifth tarsi fuscous to black. Tegulae hyaline, usually slightly yellow posteriorly. Wings hyaline; venation pale yellow.

HEAD. 1.1 (range 1.02–1.18) times as broad as mesoscutum; in dorsal view 2.25 (2.07–2.52) times as broad as long, with temples rounded off and between one third and one fourth as long as eyes; the distance between posterior ocelli (POL) 2.11 (1.75–2.80) times oculo-ocellar distance (OOL). Head in front view suboval with the genae moderately buccate. Eyes separated about 1.59 (1.18–1.74) times their length. Malar space more than half (0.68 (0.55–0.76)) the length of an eye. Breadth of oral fossa 1.93 (1.69–2.36) times malar space. Clypeus strigose, its anterior margin moderately emarginate. Head uniformly and moderately reticulate. Antennae inserted low on head, lower edge of toruli at or hardly above level of ventral edge of eyes; distance between clypeal margin and toruli 0.69 (0.54–0.8) times the distance between median ocellus and toruli. Scape length 1.23 (1.09–1.4) times eye length, scape almost reaching lower edge of median ocellus; combined length of pedicellus and flagellum 0.87 (0.76–0.96) times breadth of head; pedicellus (profile) 2.06 (0.75–2.5) times as long as broad, about as long as anelli plus first funicular segment; flagellum rather weakly clavate, proximally as stout as or slightly

.

stouter than pedicellus; first and second anelli short, twice or slightly more than twice as broad as long, third anellus longer than previous anellus and about 1.5 times as broad as long; funicular segments subquadrate, proximal ones sometimes slightly longer than broad, distal ones occasionally very slightly transverse; clava 1.9 (1.5–2.29) times as long as broad, 0.83 (0.66–1.15) as long as three preceding funicular segments together; sensilla in one row on each segment, sparse on funicle, more numerous on the clava.

MESOSOMA. 1.52 (1.38–1.74) times as long as broad. Pronotal collar moderately long medially, 0.21 (0.16–0.26) times (one sixth to one fifth) as long as mesoscutum, and much longer at sides, strongly and coarsely reticulate, clearly margined. Mesoscutum 1.58 (1.28–1.82) times as broad as long, rather coarsely reticulate discally, more finely laterally, without piliferous punctures. Scutellum 0.9 (0.82–0.94) times as broad as long, moderately convex, finely reticulate, frenum slightly more coarsely reticulate. Axillae finely reticulate. Dorsellum a narrow, alutaceous transverse crest separated from scutellum by simple suture. Propodeum medially slightly less than half (0.41 (0.36–0.48)) as long as scutellum; median area 2.39 (2–3) times as broad as long, well-defined laterally, plicae distinct throughout and sharp over at least their distal half; median carina distinct, straight; panels of median area finely, slightly irregularly reticulate; nucha transversely aciculate, separated from median area by impressed line; posterior foveae, at sides of nucha, moderately deep; spiracles oval, longer than broad, separated by nearly half their length from metanotum. Postspiracular sclerite broad, shiny, weakly and irregularly sculptured. Mesepisternum moderately finely reticulate, its upper triangular area smooth; mesepimeron rather more coarsely reticulate than mesepisternum, metapleuron smooth. Legs rather short; femora rather stout; mid tibiae fairly slender, 7.44 (4.88–9) times as long as their maximum breadth. Fore wing rather broad; costal cell fairly broad, its upper surface bare, lower surface with a complete row of hairs and some additional hairs scattered over distal third to half; basal cell bare, open below; basal vein bare or with one to three hairs; speculum open below, on upper surface of wing extending below proximal end of the marginal vein; surface beyond speculum thickly pilose; marginal vein 2.19 (2–2.47) times as long as stigmal vein; postmarginal vein shorter than marginal, 0.73 (0.63–0.81) times as long as marginal.

METASOMA. Ovate, 1.24 (1.16–1.33) times as long as mesosoma, 0.8 (0.66–0.96) times as broad as mesosoma, 2.37 (1.91–2.96) times as long as broad; basal tergite occupying from slightly more than one quarter to nearly one third of total length; last tergite somewhat shorter than basal breadth, its length 1.07 (0.72–1.79) times its breadth; ovipositor sheaths projecting at most very slightly; hypopygium slightly reaching the middle of metasoma, ratio of hypopygium length to metasoma length is 0.44 (0.35–0.54).

Male

LENGTH. 1.8 to 2.25 mm (N = 15, mean = 2.02, sd = 0.16 mm).

COLORATION. Head and mesosoma bright green; metasoma greenish dorsally with second tergite (T2) and posterior half of first tergite (TI) yellow, third tergite (T3) purplish; antennae bright testaceous; legs except coxae yellow, last tarsal segments grey-brown.

HEAD. Antenna with 3 anelli and 5 funicular segments, length of pedicel plus flagellum 0.97 (0.85–1.04) times as breadth as head; scape 5.33 (4.6–6.25) times as long as broad, without a boss on its anterior surface; flagellum proximally not broader than pedicel, F1-F4 longer than broad, F5 subquadrate. Mouthparts unmodified; no patch of modified sculpture behind malar sulcus.

MESOSOMA. Pronotal collar as long as in females, about 0.21 (0.18–0.27) times mesoscutal length. Middle tibiae unmodified, 7.42 (6.29–8.8) times its breadth, tibial spur 1.47 (1.17–1.8) times breadth of first tarsus.

METASOMA. Oblong, ovate, 0.91 (0.83–1.02) times as long as mesosoma, 2.24 (1.63–2.63) times as long as broad with a yellow ventral plica; T1 with triangular depression at base.

Morphological comparison

Females of Mesopolobus robiniae sp. nov. were not identifiable based on Graham’s keys ( Graham 1969), but several morphologically and morphometrically related species were found for which the differing characters will be enumerated in the order that the species appear in Graham’s key. The species M. robiniae sp. nov. has a shorter metasoma compared to head plus mesosoma in M. maculicornis . The species M. jucundus (Walker, 1834) has a curved stigmal vein compared to M. robiniae sp. nov. Mesopolobus robiniae sp. nov. differs from M. fasciiventris by its males having 3 anelli and 5 funicular segments while in the latter there are 2 anelli and 6 segments. Females of M. robiniae sp. nov. differ from those of M. fasciiventris in the ratios of pcl.l3/mav.l and clv.l/ hea.l (for abbreviations see Table 2 , for differences Table 3 ). The head of M. apicalis in dorsal view has temples nearly three quarters as long as the eyes, while M. robiniae sp. nov. has its head in dorsal view with temples appearing one quarter to one third as long as the eyes. The metasoma of M. amaenus is less than twice as long as broad and almost as long as the mesosoma, while in the case of M. robiniae sp. nov. the metasoma is not less than twice as long as broad, but it is as long as the mesosoma. The species M. longicollis has the pronotal collar 1/7 to 1/6 as long as the mesoscutum and its metasoma is less than twice as long as broad compared to M. robiniae sp. nov. The species M. diffinis and M. meditteraneus differ from M. robiniae sp. nov. because the latter has longer marginal vein (1.4 to 1.6) than length of the stigmal vein.

The species M. verditer is not present in the keys of Graham (1969) because it has a North American distribution. It differs from M. robiniae sp. nov. in the following: antennal funicle segments shorter than their breadth, while in M. robiniae sp. nov. they are at least as long as their breadth. The ratio of the stigmal vein to the last gastral tergite length is 1.91–2.50 in M. verditer , while in M. robiniae sp. nov. is between 0.08–1.15. Mesopolobus sericeus differs from M. robiniae sp. nov. first by having 2 anelli and 6 funicular segments, but also in having the ratio of the stigmal vein to the last gastral tergite length 1.41, while in the other species this ratio is smaller (0.8–1.15). In M. typographi the median area of the propodeum is 1.75–2 times as broad as long ( Graham 1969) while in M. robiniae sp. nov. is 0.82–0.94 times as broad as long (N = 15).

Based on von Rosen’s key ( von Rosen 1958), the morphological identification of specimens led us to M. mediterraneus as the closest species, from which females of M. robiniae sp. nov. differs, apart from the previously mentioned longer marginal than stigmal vein, in also having a longer pronotal collar and a shorter metasoma than the combined length of head and mesosoma.

Gahan (1932: 739) states that Mesopolobus (syn. Amblymerus ) verditer ( Norton 1868) “…conforms very closely to the characters of the genus Amblymerus Walker as represented by Amblymerus amoenus Walker …” (syn. M. amaenus ), when transferring the species to the genus Amblymerus Walker, 1834 from the genus Nasonia Ashmead, 1904 . The hosts of M. verditer are usually sawflies ( Hymenoptera : Diprionidae ) on pines ( Pinus sp.) ( Noyes 2020). Mesopolobus verditer is distributed in the Nearctic and Germany ( Thompson 1958). Moreover, M. verditer differs from M. robiniae sp. nov. in having a reticulated middle area of propodeum and oblique wrinkles, as does also from M. amaenus and M. longicollis ( von Rosen 1958) .

We propose the following update to the key of Mesopolobus species of Graham (1969) for females:

16. Either metasoma at least slightly longer than head plus mesosoma, and usually more than twice as long as broad, or metasoma not longer than head plus mesosoma, and at most twice as long as broad ..........................................................................................................................................16A

– Metasoma not longer than head plus mesosoma, their ratio is 0.94 (0.88–0.98), metasoma usually more than twice, 2.37 (1.91–2.96) times as long as broad .............................................................. ............................................................................................ M. robiniae Lakatos & László sp. nov.

16A. Metasoma at least slightly longer than head plus mesosoma, usually more than twice as long as

broad ............................................................................................................................................ 17 – Metasoma not longer than head plus mesosoma, at most twice as long as broad ....................... 27

Distribution

The type locality for M. robiniae sp.nov. is Săldăbagiu de Munte, Bihor County, Romania (47.096354° N, 21.984963° E). The other localities are situated in the neighbouring counties: Cluj County, Romania and Hajdú-Bihar County, Hungary. The species may appear in the Carpathian Basin where its host plant is present, but we expect that it may also be found outside of the Carpathian Basin, in Eastern Europe and maybe throughout Europe.

Biology

Based on our rearing, M. robiniae sp. nov. seems to be an early flying parasitoid species. Individuals of the species emerged during spring consequently in all study years. Our black locust seedpod samples were collected mostly in March, and the emergence peak of M. robiniae sp. nov. was in April, with a decrease in May. After May, we rarely encountered any individuals of this parasitoid species.

The host of M. robiniae sp. nov. may be Bruchophagus robiniae but there is no information regarding the host plant of B. robiniae before the introduction of black locust. Another possibility is that M. robiniae sp. nov. initially had another host, but switched from it to B. robiniae . Either possibility is plausible; before 1970 ( Zerova 1970) the species B. robiniae was not known, and M. robiniae sp. nov. was not described until now. The parasitoid community of black locust is understudied, and the available literature makes no mention of parasitoids in this community ( Farkas & Terpó-Pomogyi 1974; Perju 1998), with the exception of our ecological study concerning the seed-predator community of black locust in Eastern Europe ( Lakatos et al. 2016).

Figures

Fig. 5 (opposite page). Mesopolobus robiniae Lakatos & László sp. nov. a–b, e–f, i. ♀ (MZBBU HYM000034). c–d, g–h, j. ♂ (MZBBU HYM000035). k. Paratype, ♀ (MZBBU HYM000014). l. ♂ (MZBBU HYM000036). a. Head, frontal view. b. Antenna. c. Head, frontal view. d. Antenna. e. Mesosoma. f. Fore wing. g. Mesosoma. h. Fore wing. i. Gaster, dorsal view. j. Gaster, dorsal view. k. Habitus. l. Habitus. Scale bars: a–j = 0.1 mm; l–k = 0.5 mm