Brachyelatus marthae Burks, Krogmann & Heraty, 2019

Burks, Roger A., Krogmann, Lars & Heraty, John M., 2019, Chrysolampine Wasps (Chalcidoidea: Perilampidae sensu lato) From Baltic Amber, Insect Systematics and Diversity (AIFB) 3 (6), No. 10, pp. 1-5 : 2-4

Chrysolampinae

Brachyelatus marthae Burks, Krogmann & Heraty sp. nov.

( Figs. 1–6 )

(Zoobank LSID: urn:lsid:zoobank.org:act:9FE4DB0B-FC42-4949-8E5B-978C456E8A62 )

Diagnosis. Fore wing stigma with a long narrow uncus, and with uncal sensilla arranged in a straight line ( Fig. 5 : cs). Axillae broadly separated medially; therefore, mesoscutellar disc truncate anteriorly ( Fig. 2 ). Mesoscutellar disc with chiefly transverse sculpture (otherwise smooth).

Female. Body length 1.3–1.9 mm (n =4).

Head with slightly elevated vertex and therefore subcircular in anterior view, irregularly sculptured, but generally coriaceous to imbricate, with very short setae, eye height slightly over half head height, antennal scrobe broad, interantennal prominence present and rounded, toruli near center of face; clypeus distinguished by transition in sculpture to being nearly smooth, also laterally by a shallow indentation; anterior tentorial pit near mouth margin, far ventral to dorsal margin of clypeus as indicated by sculpture ( Fig. 6 : atp); malar sulcus distinct; mouth margin broad and essentially straight in anterior view; hypostomal carina with dorsal extension and therefore subforaminal bridge likely similar to that of other chrysolampines. Mandible with two teeth. Flagellum subequal to scape in length; all funiculars transverse, second flagellomere only about twice the length of the anellus but bearing multiporous plate sensilla ( Fig. 6 : Fu

1

); clava over half funicle length.

Mesosoma. Pronotum short, without transverse carina, uniformly sculptured and setose dorsally up to posterior smooth strip (which is indicated only by being posterior to the largest transverse row of setae); propleura diverging posteriorly ( Figs. 3–4 ), prosternum without any groove along discrimenal line. Mesoscutum transversely imbricate anteriorly to coriaceous posteriorly; notaulus deep and distinct but ending slightly before transscutal articulation; mesoscutal sidelobe similar to midlobe in sculpture and setation. Axillae well-separated medially, slightly advanced, coriaceous to imbricate. Mesoscutellar disc transversely imbricate to anteriorly smooth ( Fig. 2 ), frenal line indicated by abruptly shallow sculpture on the nearly smooth frenum; axillula without distinct dorsal groove but with weaker sculpture than mesoscutellar disc; mesoscutellar rim present and strongly sculptured. Metascutellum with smooth and convex dorsellum. Propodeum with transverse row of large foveae anteriorly, with smooth and simple median carina, median panel broad and smooth. Fore wing ( Figs. 2 and 5 ) costal cell densely setose dorsally and ventrally; parastigma only slightly constricted near placoid sensilla, with a short sclerotized continuation along basal fold; marginal vein slightly thickened basally, over half as long as costal cell, less than twice as long as postmarginal vein, nearly 4× as long as stigmal vein; basal cell setose anteriorly, apically, and along basal and cubital folds; speculum present but with extensive sparse setation ventrally; fore wing stigma with long narrow uncus, and with uncal sensilla arranged in straight line ( Fig. 5 ). Hind wing with short spur-like pigmentation on its basal fold ( Fig. 2 ). Legs uniformly pale beyond the metallic coxae; metatibia densely setose, slightly expanded apically; first metatarsomere much longer than width of metatibial apex.

Metasoma. Petiole short, presumably transverse (not visible in specimens). Gaster convex and only weakly convex dorsally, Gt 1 only about twice as long as Gt 2, Gt 2 similar in length to Gt 3; Gt 6 and syntergum very short; hypopygium reaching about half gaster length ( Fig. 4 ). Cerci short. Ovipositor sheath slightly exserted.

Male. Body length 1.3 mm (n =1). Similar to the females in nongenitalic structures except: Scape in males with numerous pores in sloping depressions on medial surface ( Fig. 6 : vp).

Material examined. Holotype: Baltic amber inclusion: Eocene. [1F#, SMNS BB-2842 ]. Deposited in SMNS . Paratypes: [3F#, SMNS BB-2843–SMNS BB-2845,]. [1M#, SMNS BB-2846].

Etymology. Named with love after my (RAB’s) mother, Martha Shadle, who worked hard to ensure my education in trying times.

Specimen notes. The fore wing venation of some of the paratypes may appear to be different from that in Fig. 5 at certain angles, but this is due to refraction artifacts caused by different polishing angles of the different amber facets. In the largest facet, the venation is confirmed as being the same as that figured. Two female paratypes are distinctly smaller than the others, but upon further examination we determined that they do not represent a distinct species.

Taxonomic discussion. Although B. marthae is somewhat generalized in appearance for a chrysolampine, it can be placed to the genus Brachyelatus using a suite of arguably subtle features. Because none of the diagnostic features of females is highly distinctive, B. marthae is easily confused with other generalized chalcidoid taxa, such as Pteromalidae sensu lato.

The low placement of the anterior tentorial pits relative to the apparent dorsal margin of the clypeus is a feature found in other examined chrysolampines (e.g., Chrysolampus schwarzi Crawford, 1914 ( Hymenoptera : Perilampidae ) illustrated by Darling 1986, fig. 3). Pores within funnel-like sloping depressions on the male scape were discussed by Darling (1986) and Heraty et al. (2013) as diagnostic for Chrysolampinae . The simple presence of pores on the male scape is regarded as a locally informative feature, considering that comparable pores are present in some distantly related taxa such as Eulophidae ( Schauff 1985) and Aphelinidae (Shirley et al. in press). However, pores present inside a funnel-like (sloping) depression on the scape was the diagnostic feature used by Darling as an apomorphy for Chrysolampinae . Additionally, the arrangement and number of these structures may be diagnostic as well, in that they are present in relatively large and dense clusters. Bidentate mandibles are also locally informative but the relatively long and narrow mandibular, often falcate, shape of chrysolampines is an uncommon feature in chalcidoids.

Brachyelatus marthae belongs in the group of chrysolampines having a short (‘sessile’) petiole and separate gastral terga that are similar to one another in length.Within this group, it can be excluded from Chrysomalla Förster, 1859 ( Hymenoptera : Perilampidae ) by the lack of a transverse pronotal carina. Elatomorpha Zerova, 1970 ( Hymenoptera : Perilampidae ) differs from B. marthae and all other chrysolampines in having relatively distinctive flat head shape and unusual fore wing venation (Doğanlar and Doğanlar 2014). Brachyelatus is currently defined by gestalt and/or potentially plesiomorphic features such as shape and sculpture of the head, mesoscutellum, mesopectus ventrally, gaster, and petiole (Bouček 1988), and B. marthae is consistent with these features. The labrum could not be seen on any of the fossils, but is assumed to be consistent with extant chrysolampines, and it is possible that the labrum is poorly visible in part because of presence of tapered marginal setae as in Brachyelatus viridis Hoffer & Novicky, 1954 ( Hymenoptera : Perilampidae ) ( Darling 1988, fig. 40). Other features used previously to define Brachyelatus apply to Palearctic species but not to one or either of the Australian species.

Brachyelatus marthae has a single anellus but such a feature should not be regarded as a consistently diagnostic trait of Chrysolampinae ( Darling 1986) . This is because some species possess a short second and third flagellomere that also lack multiporous plate sensilla, and others possess a second flagellomere that is not much larger than the first flagellomere ( Darling 1986, fig. 20; Doğanlar and Doğanlar 2014). The antenna of B. marthae is relatively short, as in other Brachyelatus , and the second flagellomere bears small multiporous plate sensilla.

Some previous workers ( Graham 1969, Bouček 1972, Doğanlar and Doğanlar 2014) characterized Brachyelatus as having broadly separated axillae (mesoscutellum anteriorly truncate), and B. marthae agrees with this characterization. However, Bouček (1988) described Brachyelatus flavicornis Bouček, 1988 ( Hymenoptera : Perilampidae ) as having an ‘anteriorly subangulate’ mesoscutellar disc (axillae meeting or nearly meeting anteromedially), and therefore this is a variable feature within the genus. Fore wing stigma shape and distribution of sensilla were described as diagnostic for Chrysolampinae by Darling (1986, figs. 36–45). The stigmal shape in B. marthae is similar to that of a typical chrysolampine, but the uncal sensilla are arranged in a straight line, while those figured by Darling in extant chrysolampines were in either a vaguely quadrate or L-shaped pattern. Examined extant Brachyelatus have uncal sensilla not arranged in a straight line, but this feature was determined to be too variable to use for generic distinction.The ‘spur’ vein of the hind wing along the basal fold in B. marthae is intriguing, but a similar spur was also found in various extant chrysolampines, and therefore, it is treated here as a species feature instead of a generic feature. Likewise, a densely setose metatibia was found in many other chrysolampines, and therefore this feature is noted here but not asserted to have diagnostic value for the species. While Bouček (1972) and Doğanlar and Doğanlar (2014) used the length of the first metatarsomere to help define Brachyelatus , this feature was not mentioned by Bouček (1988). We confirmed that at least the Australian species B. flavicornis possesses a relatively long first metatarsomere, and therefore this feature should not be used to define the genus on a worldwide basis.

The presence of Brachyelatus , and so far no other extant genus of Chrysolampinae , in the Eocene is consistent with Darling’s (1986) hypothesis of phylogenetic relationships of the genera: ( Brachyelatus ( Elatomorpha ( Chrysomalla + Chrysolampus ))). However, the number of chalcidoid fossils is too few to rely upon presence/absence for excluding the possibility that other known extant chrysolampine genera can also be traced back to the Eocene. Combined molecular and morphological data ( Heraty et al. 2013) indicate that Brachyelatus is instead the sister group of Chrysomalla , potentially with Chrysolampus as the sister group to this clade (the species identified as Austrotoxeuma Girault in that study is actually Brachyelatus as well). Broad separation of the axilla suggests that B. marthae may form a monophyletic group with Brachyelatus viridis Hoffer and Novicky , the type species of the genus and only other known Palearctic species. However, B. viridis possesses a short first metatarsomere, which is not found in B. marthae or any other examined species of the genus. Assuming that Brachyelatus have a similar life history to extant Chrysolampus , this discovery establishes a date for the presence of relatively soft-bodied planidiaform larvae within the planidial clade as coinciding with the more highly sclerotized larvae of Perilampinae and Eucharitidae .

Figures

Figs. 1–6. Brachyelatus marthae sp.nov.holotype and paratypes.1–5. Female, 1. Habitus (SMNS BB-2843).2. Body of holotype, dorsal view (SMNS BB-2842).3. Body,lateral view (SMNS BB-2844). 4. Body of holotype, ventral view, 5. Fore wing venation of holotype, cs =uncal sensilla.6. Male, head, anterior view (SMNS BB-2846), atp =anterior tentorial pit, Fu1 =first funicular (second flagellomere), vp =ventral pores of scape.