Masnerium wellsae gen . nov . , sp . nov . ( Hymenoptera , Platygastridae , Sceliotrachelinae ) a parasitoid of Aleuroduplidens wellsae Martin ( Hemiptera , Aleyrodidae ) in Australia

Masnerium wellsae Polaszek, gen. nov., sp. nov. is described from Merbein, Victoria, Australia. It is a primary endoparasitoid of the whitefl y Aleuroduplidens wellsae Martin, described from the same type locality with identical collection data. Masnerium is most closely related to the genera Aleyroctonus Masner & Huggert, and Aphanomerus Perkins, but diff ers from both these genera in several morphological characters that are of primary importance at genus level in the Sceliotrachelinae.


Introduction
revision of the platygastroid "subfamily" formerly called Inostemmatinae is a landmark work in the taxonomy of this relatively poorly-studied group."Platygastrids", in the broad sense, are a group of major economic importance, especially as parasitoids of gall midges (Diptera: Cecidomyiidae) which constitute the majority of their hosts.A handful of genera, Platygaster, Synopeas, Leptacis and a few others, probably contain 90% of platygastrid species.Prior to Masner and Huggert, platygastrids were divided by most authors into Inostemmatinae and Platygastrinae, based on the presence (Inostemmatinae) or absence (Platygastrinae) of a reasonably well-developed submarginal vein.Masner and Huggert (1989) showed that in these two former subfamilies, the submarginal vein is lost independently in several lineages, and is not an informative character at higher (tribe, subfamily) levels.Masnerium, described below, is no exception having its two closest relatives with well-developed submarginal veins in all their known species.
Masnerium is described below because its morphological character suite and host data are informative for our understanding of generic and higher relationships within this important group.
Morphological terminology broadly follows Masner and Huggert (1989) with modifi cations following Johnson et al. (2008).Th e holotype specimen was photographed initially as an unprocessed card-mount, using AutoMontage software, and later partially bleached using hydrogen peroxide and potassium hydroxide, and photographed as a slide mount in Canada Balsam.Th e unique holotype (dissected under six coverslips on a single microscope slide) is deposited in the Australian National Insect Collection, Canberra, Australia.Masnerium Polaszek, gen.n. urn:lsid:zoobank.org:act:D7DAEABB-8E4E-4B1B-A6FB-EDD7342E1E10Figs 1-9 Type species: Masnerium wellsae gen.n. (described below), by present designation.
Metasoma short and dorsoventrally depressed, with 8 visible tergites.T1 strongly transverse, with an anterior transverse carina and a pair of central longitudinal carinae  Metasoma short and dorsoventrally depressed, with eight visible tergites.T1 strongly transverse, with an anterior transverse carina and a pair of central longitudinal carinae diverging posteriorly (as in Helava alticola Masner & Huggert, 1989).T2 with two shallow transverse hairy pits anteriorly; strongly longitudinally striate laterally.T3-T8 setose.Genitalia with three teeth per digitus; aedeagal lobe apparently truncate.Biology.Masnerium wellsae is a primary endoparasitoid in the larvae of the aleyrodid Aleuroduplidens wellsae Martin.

Discussion
Th e structure of the male antenna strongly indicates that Masnerium is clearly closely related to both Aleyroctonus and Aphanomerus.It shares with Aphanomerus the completely fused clava, without any traces of sutures, but the position of the claval sensilla is possibly indicative of a plesiomorphic 4-segmented clava.Th is would suggest a plesiomorphic 11-segmented male antenna in this lineage.Aleyroctonus and Masnerium are, as far as is known, exclusively parasitoids of Aleyrodidae.Masner and Huggert (1989: 37, 58) drew attention to the close relationship between Aleyroctonus and Aphanomerus, although they placed them in diff erent genus "clusters" (Amitus-cluster and Aphanomerus-cluster, respectively; Masner and Huggert, 1989: 14).Th is study suggests strongly that both Aleyroctonus and Masnerium are more closely affi liated to Aphanomerus, despite sharing the hosts of Amitus.
Th ese three closely-related genera, Masnerium, Aleyroctonus and Aphanomerus share hemipteran hosts, albeit whitefl y immatures in the case of the fi rst two genera, and hemipteran (fulgoroid) eggs in the latter.Host-switching between insect eggs and the immature stages of sessile Sternorrhyncha (Coccoidea, Aleyrodidae and some Aphididae) appears to be very common in many lineages among the Proctotrupomorpha.Within the chalcidoid family Aphelinidae alone it has occurred at least fi ve times (Polaszek 1991), and may also be a common phenomenon in basal platygastroids.Acquisition of hosts that are more complex than eggs, especially if this involves overcoming host defence systems, could lead to rapid radiation, with these lineages consequently preadapted for the acquisition of increasingly resistant hosts, such as the developmental stages of Holometabola.