Triadomerini, Huber, 2017

Huber, John T., 2017, Eustochomorpha Girault, Neotriadomerus gen. n., and Proarescon gen. n. (Hymenoptera, Mymaridae), early extant lineages in evolution of the family, Journal of Hymenoptera Research 57, pp. 1-87 : 39

Tribe Triadomerini stat. n.

Notes.

Yoshimoto (1975) treated the Cretaceous amber fossils from Canada and classified Triadomerus Yoshimoto in his new subfamily Triadomerinae , Carpenteriana Yoshimoto and Macalpinia Yoshimoto in Mymarinae , and Enneagmus Yoshimoto in Trichogrammatidae . He defined his Triadomerinae as "having the submarginal and marginal veins distinctly separated at the junction of the fore wing and antennae 13-segmented in the female". Poinar and Huber (2011) keyed the Cretaceous genera of Mymaridae , adding only Myanmymar Huber from Burmese amber to bring the number of genera to five, including Enneagmus , which Huber (2005) had reclassified in Mymaridae .

I treat Yoshimoto's Triadomerinae as a tribe, defined as follows, based mainly on extant genera and species: mandible with 3 ( Borneomymar , Eustochomorpha ) or 4 teeth; pronotum entire; fore wing wide, with marginal setae much shorter than wing width; venation more than 85% of wing length, with marginal vein present and longer than submarginal vein, and with postmarginal vein present and longer than marginal vein; hypochaeta, when present, closer to proximal than to distal macrochata; hind wing wide with marginal setae shorter than wing width; tarsi 5-segmented, with tarsomere 1 distinctly longer than any of the others; petiole clearly shorter than wide, ring like. Female. Antenna with flagellum at most 11 segmented (funicle 8-segmented and clava 1-3-segmented); ovipositor usually greatly exserted beyond either posterior ( Borneomymar , Eustochomorpha ) or anterior ( Neotriadomerus ) apex of body but in the extinct genera not projecting either anteriorly or posteriorly. Male. Antenna 11-segmented, the flagellomeres each with several mps; genitalia encapsulated, with short, thick parameres, apparently without digiti (in Neotriadomerus ) but thinner walled and with digiti (in Borneomymar )

Triadomerini is treated here as the sister clade to the remainder of Mymaridae . The only apomorphy that defines the tribe is reduction in number of flagellar segments (at most 11) relative to Rotoitidae , whose species have a 12-segmented flagellum in females of both included extant genera. An additional diagnostic feature of the extant species of Triadomerini is the exserted cerci on a distinct prominence, similar to that of Torymidae . The occurrence of elevated cerci, number of teeth in mandibles, and several other features cannot definitely be determined from the fossil specimens studied. The lack of a hypochaeta apparently occurs in Triadomerus and Eustochomorpha and apparently also in at least one of the Neotriadomerus species.

Triadomerus is known only from Cretaceous amber from present day western Canada ( Yoshimoto 1975). Eustochomorpha and Neotriadomerus species are confined to Australia, and extant Borneomymar species occur in the islands of Borneo and Madagascar whereas the one extinct Borneomymar species is from Eocene amber from the Baltic region ( Engel et al. 2013). Macalpinia and especially Carpenteriana doubtfully belong in Triadomerini but perhaps are better classified here than elsewhere. Even though Carpenteriana has 7-segmented funicle and an entire clava its fore wing vena tion appears to be similar to Macalpinia . Macalpinia has an 8-segmented funicle and 3-segmented clava, as in Triadomerus and Neotriadomerus , so on the basis of this feature is classified fairly well in the tribe even though it appears to have no postmarginal vein and apparently only 4-segmented tarsi (tarsi are difficult to see; they may, in fact, be 5-segmented). Thus, I classify six genera in Triadomerini : four genera definitely- Borneomymar , Eustochomorpha , Neotriadomerus , Triadomerus , and two genera tentatively- Carpenteriana and Macalpinia .