Gonatocerus ( Cosmocomoidea ) tremulae ( Bakkendorf, 1934 )

Triapitsyn, Serguei V., 2013, Review of Gonatocerus (Hymenoptera: Mymaridae) in the Palaearctic region, with notes on extralimital distributions, Zootaxa 3644 (1), pp. 1-178 : 163-166

Gonatocerus ( Cosmocomoidea) tremulae ( Bakkendorf, 1934)

( Figs 309–316)

Lymaenon tremulae Bakkendorf 1934: 30 –33, 69– 70 (host), 126–127 (hosts). Type locality: Fortunens (as Fortunen in the original description) Indelukke, Dyrehaven (Jaegersborg Dyrehave, Zealand Island), Hovedstaden, Denmark. Reinstated as a valid species by Pricop ( 2010 b: 117) from previous synonymy under G. ovicenatus by Baquero & Jordana 2003: 16 –17 (see “Comments” below).

Lymaenon tremulae Bakkendorf : Debauche 1948: 81 (list); Hincks 1960: 210 –211 (diagnosis, records from England, UK [in part, see “Material examined”]); Viggiani 1969: 45 (illustration of F 4 –F 8 and clava of female antenna), 46 (comments, a “ type ” examined).

Gonatocerus tremulae (Bakkendorf) : Matthews 1986: 222 (in part; member of the ater species group, information on the type; diagnosis likely based primarily on misidentified specimens of G. oxypygus ); Huber 1988: 59 (closely related to G. ovicenatus ).

Type material examined. Lectotype female [ ZMUC], here designated to avoid the existing confusion regarding the type specimens of this species, on slide ( Fig. 309) labeled: “ Gonatocerus (“ ater ” group) [in J.T. Huber’s handwriting] Fort. Indelukke. 18 - 9-28. Paa Asp. Villig til at stikke Idiocerus – AEg Ƥ O. Bakkendorf.”. The lectotype ( Fig. 312) is in fair condition, complete but with a few segments of the appendages detached, mounted dorsoventrally. “Paa Asp.” means “on aspen”, “Villig til at stikke” means “eager to sting”, and “AEg” means “egg” (Lars B. Vilhelmsen, personal communication). The label information likely refers to the note by Bakkendorf ( 1934) under “Oviposition” (p. 33): “On September 19 th, 1928 I had an opportunity to observe the egglaying of Lymaenon tremulae on branches of aspen with eggs of Idiocerus (fig. 49)”. Even though this specimen was not marked by Bakkendorf as L. tremulae and the date on the label is one day earlier than the published date, it is very likely that this female was part of his unmarked syntype series of L. tremulae , particularly because it fits perfectly the original description and the illustrations: the ovipositor is only a little exserted (see Bakkendorf’s figs 44, 48, and 49, pp. 30, 31, and 33, respectively), and F 6 of the antenna (in Bakkendorf’s fig. 45, p. 31) is clearly narrower than F 5, F 7, or F 8 and thus likely lacks mps.

Type material was not designated in the original description but Viggiani ( 1969) noted that he had examined a “ type ” (apparently a syntype) of L. tremulae without providing further details, and later Matthews ( 1986) reported that he had examined the “ holotype ” [ ZMUC] collected by O. Bakkendorf on 11.viii. 1929 [according to Bakkendorf ( 1934: 69), that was the date when the parasitized eggs of the host had been collected]. That specimen was then reported as being lost from ZMUC by Baquero & Jordana ( 2003); according to John S. Noyes (personal communication), some of Bakkendorf’s type specimens of Gonatocerus were lost when they were returned to ZMUC from BMNH where they had been on loan to M.J. Matthews. Matthews’ mention of “ holotype ” is incorrect according to Article 74.5 ([ ICZN] 1999) because the original description mentioned numerous reared specimens, all of which must be considered as syntypes based on Article 72.4. 1.1 ([ ICZN] 1999). Article 74.6 ([ ICZN] 1999) does not apply in this situation.

Material examined. AUSTRIA. TYROL, Poltental [Poltental Valley], Hall in Tirol, 11.ix. 1949, E. Pechlaner [ 1 Ƥ, NHMW]. RUSSIA. MOSKOVSKAYA OBLAST’, Pushkinskiy rayon, Pushkino, Mamontovka, Sosnovka, 13.ix. 2003, V.A. Trjapitzin [ 1 Ƥ, ZIN]. PRIMORSKIY KRAY, Ussuriyskiy rayon, Gornotayozhnoye, 43.66 °N 132.25 °E, 200 m, M.V. Michailovskaya: 27–29.v. 1999 [ 1 Ƥ, UCRC]; 12– 17.viii. 1999 [ 1 Ƥ, UCRC]. UK. ENGLAND: Cumbria Co., Skirwith: 18.ix. 1952, H. Britten [ 1 Ƥ, MMUE]; 29.ix. 1948, W.D. Hincks [ 1 Ƥ, MMUE]. Dorset Co., Bournemouth, 8.x. 1982, S.G.C. Brown [ 1 female, BMNH] (misidentified by S.G.C. Brown as Ooctonus heterotomus Foerster ). North Yorkshire Co., Askham Bog, 27.v. 1947, W.D. Hincks [ 1 Ƥ, MMUE]. WALES, Bridgend Co. Borough, Kenfig Pool National Nature Reserve, 31.viii. 1995, J.S. Noyes [ 1 Ƥ, CNCI].

Distribution. PALAEARCTIC: Austria *, Denmark ( Bakkendorf 1934 [as Lymaenon tremulae ]), Russia *, and UK ( England ( Hincks 1960 [in part, as L. tremulae ]), and Wales *).

Redescription. FEMALE ( lectotype and non-type specimens). Body length 1155–1400 µm. Body ( Fig. 312) dark brown or black, appendages mostly brown to dark brown except fore tibia light brown to brown and four basal segments of all tarsi light brown.

Antenna ( Figs 310, 313) with radicle 0.26–0.27 × total length of scape, rest of scape 2.4–2.7 × as long as wide; pedicel longer than F 1; F 1 the shortest funicle segment, F 3 a little longer than F 2 or F 4, F 5 the longest funicle segment, F 6 a little shorter than F 7 or F 8; mps on F 5 ( 2), F 6 (0 or 1 [ 0 in the lectotype but 1 in the original syntype as illustrated by Viggiani ( 1969), and also at least 1 in some specimens from England]), F 7 ( 2), and F 8 ( 2); clava with 8 mps, 2.8–3.3 × as long as wide, at least a little shorter than combined length of F 6 –F 8.

Mesosoma ( Fig. 314) shorter than metasoma. Propodeum ( Figs 311, 315) with fine submedian carinae rather apart from each other, a little closer anteriorly than posteriorly, and either almost extending or extending to anterior margin of propodeum. Fore wing ( Figs 312, 316) 2.7 –3.0× as long as wide; longest marginal seta 0.22– 0.24 × maximum wing width; disc slightly infumate, bare behind venation except for 2 to 4 setae just behind stigmal vein. Hind wing ( Figs 312, 316) 12–15 × as long as wide; disc slightly infumate; longest marginal seta 1.7– 1.9 × maximum wing width.

Metasoma ( Fig. 314). Petiole 0.4–0.5 × as long as wide, slightly narrower anteriorly than posteriorly. Ovipositor occupying entire or almost entire length of gaster, sometimes projecting forward beneath petiole, and exserted beyond gastral apex by at most 0.1 × own length (but sometimes just barely exserted), 2.0– 2.1 × as long as mesotibia.

Measurements (µm) of the lectotype. Body: 1280; head: 138; mesosoma 430; gaster 707; ovipositor 750. Antenna: radicle 33; rest of scape 93; pedicel 54; F 1 34; F 2 45; F 3 56; F 4 54; F 5 69; F 6 55; F 7 64; F 8 59; clava 148. Fore wing 1230: 427; longest marginal seta 103. Hind wing 875: 72; longest marginal seta 124. MALE. Mentioned by Bakkendorf ( 1934) who also provided illustrations of the male antenna.

Diagnosis. Gonatocerus tremulae differs from the similar species G. oxypygus by the propodeal submedian carinae ( Figs 311, 315) notably more apart from each other (very close to each other in G. oxypygus , Figs 284, 294, 301) and by a relatively shorter ovipositor (at most 2.1 × as long as mesotibia and barely exserted in G. tremulae but at least 2.6 × as long as mesotibia and distinctly exserted in G. oxypygus ).

Hosts. Populicerus ? confusus (Flor) [as Idiocerus ? confusus Flor] and P. populi (Linnaeus) [as I. populi (Linnaeus) ] ( Cicadellidae : Idiocerinae ) in Denmark ( Bakkendorf 1934).

Comments. As first noted by Viggiani ( 1969), distribution of mps on the funicle segments was indicated incorrectly in the original description of G. tremulae (only on F 8). Among specimens I have seen most lack mps on F 6 of the female antenna except for the female from Mamontovka, which has 1 mps on F 6, the female from Askham Bog, and one of the females from Skirwith, which apparently have at least 1 mps on F 6 (both are dry-mounted). Viggiani ( 1969) indicated that F 5 –F 8 have mps and illustrated F 6 with only 1 mps. Matthews ( 1986) stated that in G. tremulae F 6, F 7, and F 8 bear 2 mps and F 6 may have 1 or 2 mps but all his specimens from Buckinghamshire and Surrey were misidentified; they belong to G. oxypygus .

It would be desirable to obtain fresh specimens of G. tremulae from aspens in or near the type locality of this species in Denmark. Unfortunately, no aspen trees could be located in the type locality in September 2010 (Lars B. Vilhelmsen, personal communication).

Pricop ( 2010 b) reported, diagnosed, and illustrated supposedly G. tremulae from Romania but his identification was not based on a comparison with the type material. Rather, his specimens represent G. oxypygus with relatively short ovipositors that are not bent down at apex and are exserted beyond gastral apex by about 0.2 × own length (that is within the known variation range of G. oxypygus and very similar to its neotype); Viggiani ( 1988) and Viggiani & Jesu ( 1988) also misidentified such specimens from Italy ( Figs 297–299) as Lymaenon tremulae , and Donev ( 2005) reported similar specimens from Bulgaria as G. tremulae . At least in one of the specimens from Romania mentioned and illustrated by Pricop ( 2010 b), a female from Cucoräni that I have examined, the submedian carinae on the propodeum are subparallel and close to each other (as typical for G. oxypygus ) and not joining together at apex of dorsellum although Pricop in his fig. 1 -i ( 2010 b, p. 114) illustrated its propodeal submedian carinae as joining together at apex of dorsellum (also seen in his fig. 1 -j). That illustration, however, was based on the specimen from Cucoräni whose mesosoma was slide-mounted semi-laterally at an angle so that the propodeal submedian carinae were not properly visible. With Emilian Pricop’s kind permission, its body was remounted dorsoventrally at UCRC in 2012 from Faure’s medium into Canada balsam, and it became clear that its propodeal submedian carinae are identical to those of G. oxypygus whereas in the lectotype of G. tremulae and other conspecific specimens from northern Europe the propodeal submedian carinae are significantly more apart from each other. Resurrection of G. tremulae as a valid species by Pricop ( 2010 b) was correct, even though based on misidentified specimens.