Holopyga fervida (Fabricius, 1781)

Rosa, Paolo & Zettel, Herbert, 2018, First record of gynandromorphism in the subfamily Chrysidinae (Hymenoptera: Chrysididae), Linzer biologische Beiträge 50 (1), pp. 801-808 : 802-804

Description of the gynandromorph of Holopyga fervida (FABRICIUS, 1781)

Body length: 6.2 mm.

Head. General appearance female-like ( Figs. 1A , 2A ). Red-purple, with blue scapal basin. Frons, vertex, gena, face between eye, and scapal basin with tiny and shallow punctures, 1-3 puncture diameters apart, separated by polished interstices; scapal basin asetose and smooth; ocellar-triangle isosceles; postocellar line distinct and deep; antennae 13-segmented; in dorsal view, angular margins of the head (temples) as acute angles.

Mesosoma. Female-like, except for a male mosaic area on pronotum. Pronotum medially divided into a left masculine and a right feminine part ( Figs. 1A , 2A ). The most evident difference is colour: the left side is emerald green as typical for males, in contrast with the red-purple colouration of the female body. Yet, the punctation of this area is critical for a sexual assignment: male punctation is coarser, with larger punctures closer, and micropunctate on interstices, whereas the female's pronotum has sparser punctures, without micropunctation on interstices, but with smooth intervals (comp. Figs. 1 B-C). Mesoscutum, mesoscutellum, metanotum, propodeum, and mesopleuron female-like, with mesoscutum and mesoscutellum red-purple, the latter largely impunctate and apically with large punctures, with greenish-blue bottom; mesopleuron, metanotum, and propodeum dark blue, metanotum with foveate-reticulate punctures.

Metasoma. Female-like, terga red-purple, sterna brownish. Terga evenly punctate, with small punctures about one puncture diameter apart; laterally with denser punctures. Apical margin of metasomal terga impunctate or shallowly punctate, brownish; apex of third metasomal tergum with raised brownish rim.

Identification and variability of Holopyga fervida

Holopyga fervida is a typical example of a strongly sexually dimorphic species of Chrysididae , males and females being differently coloured, shaped and sculptured. The female is mostly shiny red-purple, with legs, metanotum, mesopleuron, propodeum, and lower part of head blue; conversely, the male is entirely green to blue-green, sometimes with golden reflections on metasoma and occasionally with golden reflections also on head and mesosoma ( var. taorminensis TRAUTMANN, 1922; Fig. 2E ). The habitus is different: the metasoma of the female is elongated, whereas that of the male has a regularly rounded posterior margin. The body punctation is also considerably different: the female has small, sparse punctures with polished interstices; the male has a coarse, double punctation, with tiny dots on interstices. Significantly different is the punctation of the mesoscutellum, almost entirely polished in female ( Fig. 1C ) and densely micropunctate in male ( Fig. 1B ).

In Northern Europe, the male can be confused with H. metallica DAHLBOM, 1854, but it is recognizable for the coarser and denser metasomal punctation, with interstices smaller than a puncture diameter, whereas in H. metallica the metasoma punctation is fine and sparse (see pictures in PAUKKUNEN et al. 2015). The female of H. metallica is easily recognizable because its colour and sculpture are similar to the male. In Eastern Mediterranean countries, the Near East and Middle East H. fervida can be confused with H. buyssoni MERCET, 1902 (often considered as its eastern subspecies), but both sexes of this species are recognizable by large and coarse punctures on the metasoma.

For a very long time, males and females of Holopyga fervida were considered different species because of the remarkable sexual dimorphism. The male had been considered a valid species named either H. curvata (FÖRSTER, 1853) or H. chloroidea (DAHLBOM, 1854). TRAUTMANN' s (1922) hypothesis that H. curvata could be the male of H. fervida was not immediately accepted (e.g., INVREA, 1923). Still LINSENMAIER (1959, 1968, 1969) considered H. chloroidea as the separate subspecies of H. fervida distributed in Asia Minor, Syria, Palestine, and Cyprus. His interpretation, even though not in contrast with the original distribution of H. chloroidea, was a source of taxonomical instability and for this reason ROSA & XU (2015) designated the lectotype of H. chloroidea. This eastern Mediterranean species with an obvious coarser punctation is currently referred to as H. buyssoni.

The Paris Museum houses an interesting female specimen of H. fervida with the aberrant colour of a male. It was collected near Paris and erroneously designated as the lectotype of H. chloroidea by KIMSEY (1986) (see ROSA & XU 2015). A second female of such colour was collected by Fritz Blühweiss in the Danube wetlands ("Donauauen") in eastern Austria (probably in or close to Vienna). This specimen ( Fig. 2D ), housed at the Vienna Museum, has been labelled by Karl Hammer as the type of " Holopyga fervida var. viridis ", but it was never formally described.

Males of H. fervida can be very variable in colour ( Figs 2B, 2E, 2F ). The typical colour is green, but several specimens from all over Europe are entirely deep blue ( Fig. 2F, H . fervida violacea HOFFMANN, 1935) or green with golden metasoma. In the southernmost European localities, males can be variably golden red. An extreme colour form was described as H. fervida taorminensis TRAUTMANN, 1922 ( Fig. 2E ).

The specimen here described as a gynandromorph shows the left half of the pronotum green and with coarse and double punctation, referable to a phenotypic trait of the male, while all other features are that of a female. The aberrant character of this specimen is very obvious. The authors presently do not have an explanation why gynandromorphism is so rare in cuckoo wasps, compared to some other families of Aculeata like spider wasps or bees, where this phenomenon is more frequently observed (e.g., WAHIS 1996, MICHEZ et al. 2009).

Figures

Fig. 1: Holopyga fervida, head and mesosoma: (A) gynandromorph; (B) male; (C) female.

Fig. 2: Holopyga fervida, habitus: (A) gynandromorph; (B) male, normal colour; (C) female, normal colour; (D) female, green variation; (E) male, holotype of H. fervida var. taorminensis; (F) male, holotype of H. fervida var. violacea. Scale bars: 1.0 mm.