Dendrocerus arietinus (Provancher, 1887) Trietsch & Mikó & Ezray & Deans, 2020

Trietsch, Carolyn, Mikó, István, Ezray, Briana & Deans, Andrew R., 2020, A Taxonomic Revision of Nearctic Conostigmus (Hymenoptera: Ceraphronoidea: Megaspilidae), Zootaxa 4792 (1), pp. 1-155 : 92-93

Dendrocerus arietinus (Provancher, 1887) , new combination

Figs. 49 , 50

Species Comments and History. Isostasis arietinus Provancher, 1887 was described from a single female specimen. Provancher named the species arietinus or “tête de belier” after the curve of the antennae, which he believed resembled the horns of a ram. Provancher (1888) transferred the species from Isostasis to the genus Baeoneura , another genus described by Förster (1856). Harrington (1900) transferred the species from Platygastroidea to Ceraphronoidea , remarking that the description “answers very well to Megaspilus Harringtoni, Ashm. ”, and Kieffer (1914) subsequently redescribed the species and transferred it to Conostigmus . Gahan and Rohwer (1917) designated a Baeoneura arietina specimen as a lectotype at the ULCQ, and noted that the specimen was badly glued. Masner (1969) echoed this statement on the condition of the specimen and reported that the specimen was a Conostigmus species.

Provancher (1887) originally described the species arietinus as a member of the genus “ Isostasis ”, which Provancher attributed to Förster; however, Förster never described a genus “ Isostasis ”. Instead, Förster had described the platygastrid genus Isostasius ( Hymenoptera , Platygastridae ) ( Förster, 1856). Dessart (1996) later designated Isostasis Provancher, 1888 not as an incorrect spelling but as a valid genus that was synonymous with Conostigmus Dahlbom, 1858 . Johnson and Musetti (2004) do not accept Dessart’s action and instead consider Isostasis as a misspelling of Förster’s Isostasius , pointing out that such an action would set a precedent leading “to the adoption of untold numbers of junior homonyms!” (pg. 6).

We mention the troubled history of this species to comment that Dessart did not directly observe the holotype, but considered the species a Conostigmus based on the assertions of Kieffer (1914) and Masner (1969). Upon examining the female lectotype specimen of Conostigmus arietinus (Provancher), 1887 at the ULQC, however, we realized that this specimen was a Dendrocerus based on its close resemblance to the female holotype of D. penmaricus (see Figs. 49 , 50 for comparison with the female holotype of Dendrocerus penmaricus (Ashmead), 1893 deposited in the USNM). The species also has the following combination of Dendrocerus -like characters: ocelli in an obtuse triangle (POL greater than LOL), where the two posterior ocelli are closer to the compound eyes than to each other (POL greater than OOL); mesometapleural sulcus arched; and facial pit absent.

This species likely belongs to the D. penmaricus species group, and may even be the same species as D. penmaricus , as the female type of arietinus shares the following characters with the female holotype of D. penmaricus : ocelli in an obtuse triangle; facial pit absent; median process on the intertorular carina present and blunt; preoccipital furrow present and the anterior end reaching the anterior ocellus; postocellar furrow absent; mandibles with two teeth; posterior end of the notaulus not adjacent to the median mesoscutal sulcus; and the general habitus (in particular, the shape of the head and the size of the eyes in relation to the head in lateral view are unique). The type specimen of arietinus is so poorly glued that it is not possible to confirm the absence of a sternaulus, which would be another indicator that this species is indeed a Dendrocerus .

Because the female type is in such poor condition and the male of the species is unknown, it is not possible to confirm whether D. arietinus is synonymous with D. penmaricus . For now, we consider D. arietinus and D. penmaricus as separate species, but we move D. arietinus from Conostigmus to Dendrocerus and consider D. arietinus as a member of the D. penmaricus species group.

Material Examined. Lectotype female: CANADA: PSUC _ FEM 148706 ( ULQC).

Figures

FIGURE 49. A. The female type specimen of Conostigmus arietinus Provancher, 1887 from the ULQC in dorsal view (PSUC_ FEM 148706), now Dendrocerus arietinus (Provancher, 1887). B. The female holotype specimen of Dendrocerus penmaricus (Ashmead, 1893) at the USNM in dorsal view (USNM Type no. 58969) for comparison.

FIGURE 50. A. The female type specimen of Conostigmus arietinus Provancher, 1887 from the ULQC in lateral view (PSUC_ FEM 148706), now Dendrocerus arietinus (Provancher, 1887). B. The female holotype specimen of Dendrocerus penmaricus (Ashmead, 1893) at the USNM in lateral view (USNM Type no. 58969) for comparison.