Arketypon vaderi, Guerrieri & Noyes, 2002

Guerrieri, Emilio & Noyes, John S., 2002, An unusual genus and species of Encyrtidae (Hymenoptera: Chalcidoidea) from Australia reared from soft scale insects (Hemiptera: Coccidae), Journal of Natural History 36 (4), pp. 443-448 : 446-447

Arketypon vaderi sp. nov.

(®gures 1±10)

Female (HOLOTYPE)

Length 1.63 mm.

Body (®gure 1) shining black; scape and pedicel brown, ¯agellum pale yellow; fore wing (®gure 5) strongly infuscate, with apex paler and two paler stripes especially in the basal third; hind wing hyaline with a brown circular spot in the middle of marginal vein; legs shiny black, tarsi pale yellow save basal segment brown. Head (®gures 2, 3) with ocelli forming a strongly obtuse angle, posterior ocellus very slightly nearer eye than occipital margin; torulus separated from mouth margin by about three times its own length and from other torulus by nearly six times its own length; proportions of antennae as in ®gure 4, scape about as long as broad, linear sensillae on all funicular segments and clava. Relative measurements: HW 125, FV 80, POL 41, AOL 22, OOL 16, OCL 11, EL 40, EW 25, MS 40, SL 14, SW 19.

Thorax with longer, shiny, setae along lower margin of scutellum; fore wing (®gures 5±7) short and wide; propodeal spiracle small, situated on the postero-lateral corner of the propodeum and slightly raised, separated from anterior margin of propodeum by more than its own diameter. Relative measurements: FWL 150, FWW 83.

Gaster with last tergite more or less straight.

PARATYPE. Ovipositor as in ®gure 8. Relative measurements: OL 68 , LTL 65 , LTW 115 , MT 63 .

Male

Identical to female but for antenna with unsegmented clava (®gure 9) and genitalia (®gure 10). Relative measurements: AL 60, MT 62.

Variation. Virtually none in the material available.

Hosts. Reared as a gregarious endoparasitoid of Myzolecanium sp. (Homoptera: Coccidae ) found in the nest of Camponotus sp. ( Hymenoptera : Formicidae ) nesting in a hollow stem of Sonneratia alba Sm. (Sonneratiaeceae) .

Distribution. Australia (Northern Territory).

Material examined. HOLOTYPE /, Australia, Northern Territory, Darwin, ex body cavity of Myzolecanium sp. in nest of Camponotus sp. , in hollow stem of Sonneratia alba , November 1998 (M. G. Nielsen). PARATYPES: Australia, 6/, 3?, same data as holotype. Holotype in ANIC, paratypes in ANIC, BMNH, CNC.

Discussion

The absence of paratergites and complete separation of the outer plates of the ovipositor from the ninth abdominal tergite clearly places Arketypon in the subfamily Encyrtinae . A number of characters, especially of the head, fore wing and abdomen place the genus somewhere within the tribes Eugahanini, Neocladiini, Prionomasticini, Encyrtini and Aethognathini (sensu Trjapitzin, 1973, 1989) although it has been suggested that these tribes could be treated as one ( Noyes and Hayat, 1984). These tribes can be characterized collectively by the fore wing venation which includes a relatively short marginal vein with a long postmarginal vein, a long curved stigmal vein which generally has the apical placoid sensillae more or less arranged in a line and the uncus absent, and the ovipositor very broad with strongly triangular outer plates and relatively broad second valvifers which are seamlessly fused to the third valvulae (gonostyli). The assignment of Arketypon in any one of the above named tribes is not easy because it shows so many unique specializations. On the one hand, the relatively simple, sickle-shaped mandible suggests that the genus may be most closely related to genera of the tribes of Eugahaniini or Neocladiini. On the other hand, the known hosts of the genera of this group might suggest a closer relationship with the Encyrtini or Aethognathini. The type species of Arketypon has been reared from scale insects, as have species of the tribes Encyrtini and Aethognathini, whereas species of the other tribes are endoparasitoids of auchenorrhynchou s Homoptera such as Cicadellidae (EugahaniiniÐ Eugahania , NeocladiiniÐ Neocladia , possibly also PrionomasticiniÐ Hexacladia ), Cercopidae (NeocladiiniÐ Carabunia ), Membracidae (PrionomasticiniÐ Prionomastix ), or even Heteroptera such as Pentatomidae , Coreidae , Scutelleridae and Pyrrhocoridae (PrionomasticiniÐ Hexacladia ).

Where their biology has been studied in detail, the included species of the abovementioned genera pupate inside the living host which then dies only after the adult parasitoids have completed their development and emerged. This is seemingly accomplished by the developing parasitoid inducing the hosts tracheal system to develop abnormally and anastomose with the cocoon of the pupating host enabling the pupal stage to utilize atmospheric air via the host’s tracheal system. This phenomenon has been observed in at least Encyrtus infelix ( Embleton, 1904) , Hexacladia linci ( Rasplus et al., 1990) and an undescribed species of Prionomastix in Costa Rica (Paul Hanson, personal communication).