Megastigmus helinae Roques & Copeland

Roques, Alain, Copeland, Robert S., Soldati, Laurent, Denux, Olivier & Auger-Rozenberg, Marie-Anne, 2016, Megastigmus seed chalcids (Hymenoptera, Torymidae) radiated much more on Angiosperms than previously considered. I- Description of 8 new species from Kenya, with a key to the females of Eastern and Southern Africa, ZooKeys 585, pp. 51-124 : 67-70

Taxon classification Animalia Hymenoptera Torymidae

Megastigmus helinae Roques & Copeland sp. n.

Type material.

Holotype ♀, Kenya, Scandent climber, Rift Valley Prov. Matthews Range, 1.1777°N, 37.3141°E, 1342m, 16 Jan 2004, ex. Helinus integrifolius fruits, A&M coll. N°2692, R. Copeland leg. (NMKE).

Paratypes. 2♀♀, same collection data as holotype (ARC, 1 destroyed); 2♂♂, same collection data as holotype (NMKE, ICIPE).

Description.

Holotype ♀. A small species with body length 3.2 mm (without ovipositor); length of ovipositor sheaths 0.8 mm. Body colour nearly entirely orange-yellow (Figures 15, 16). Head orange with a black ring around each ocellus. Pilosity on lower face pale, but black hairs on malar space, gena, and on dorsum of head, with a row of long hairs on vertex behind ocelli. Antenna entirely yellow. Pronotum orange; remainder of thorax orange except a bisinuate black band along pronotum suture at the anterior part of mid-lobe of mesoscutum (Figure 16), and two small black spots at wing insertions. Pilosity black on thorax dorsum; sparse long hairs on pronotum and mid-lobe of mesoscutum along notauli; scutellum with 3 pairs of black hairs on the sides. Legs entirely pale yellow. Forewing stigma brown without infuscation; basal cell well defined, with disc including 8 long setae, closed by a basal setal line with 8 long hairs and a costal setal line with 6 long hairs; coastal cell with several rows of small setae (Figure 21). Propodeum orange with a narrow, curved black stripe on the center of its anterior part; propodeum hairs black. Gaster entirely orange, with black hairs on sutures. Ovipositor sheaths black, very short, only 0.6 × as long as gaster, 0.2 × as long as body (Figure 16).

Head transverse (Figure 18), width: height ratio: 1.3 in dorsal view; POL: OOL: 0.8; torulus 1.2 × as long as wide; inter-antennal area as broad as torulus width; scrobe elongate, ca. 2.3 × as long as wide; Scape 1.2 × as long as combined length of pedicel, anellus and F1 (Figure 19); scape 0.8 × as long as combined length of pedicel, anellus, F1 and F2; anellus subquadrate; F1 1.2 × as long as pedicel, 1.9 × as long as wide; F2 1.8 × as long as wide; following funicular segments progressively tending to subquadrate from F4 on, with F7 1.3 × as long as wide. Pronotum, mid- and lateral lobes of mesoscutum, with coarse transverse carinae (Figure 20); axilla with longitudinal striae; mid-lobe of mesoscutum 1.1 × as long as scutellum. Scutellum 1.3 × as long as wide, with irregular transverse striae; frenum 0.3 × as long as scutellum length, mostly smooth with a few longitudinal carinae on sides. Forewing stigma oval, about 1.5 × as long as wide (Figure 21); upper part of stigmal vein elongate, 0.4 × as long as stigma length; uncus 0.6 × as long as upper part of stigmal vein; marginal vein 0.8 × as long as postmarginal vein. Propodeum with coarse longitudinal carinae, and a median carina interrupted in the middle (Figure 20).

Male. Body colour similar to that of female (Figures 22, 23), orange-yellow with a few black markings: a ring around each ocellus, a transverse fuzzy band on the center of the anterior part of propodeum, a large spot on T3 at gaster insertion, a comma- like spot on the lateral sides of T4, and a smaller, rounded, brownish spot on the lateral sides of the three following tergites. Pilosity as in female. Forewing stigma brown without infuscation (Figure 28); basal cell well defined, the disc with 11 long setae, closed by a basal setal line with 7 long setae and a costal setal line with 6 long setae; coastal cell with several rows of small setae.

Head rectangular (Figure 25), width: height ratio: 1.5 in dorsal view; POL: OOL 0.9; torulus 1.2 × as long as wide; inter-antennal area 0.9 × as wide as torulus width; scrobe 2.5 × as long as wide. Scape 1.1 × as long as combined length of pedicel, anellus and F1 (Figure 26); scape 0.8 × as long as combined length of pedicel, anellus, F1 and F2; F1 1.3 × as long as pedicel, 2.1 × as long as wide; F2 2.0 × as long as wide; following funicular segments also elongate, with F7 1.5 × as long as wide. Pronotum, mid- and lateral lobes of mesoscutum, with coarse transverse carinae (Figure 27); axilla with longitudinal striae; mid-lobe of mesoscutum short, 0.9 × as long as scutellum. Scutellum 1.2 × as long as wide, with irregular, transverse striae; frenum 0.3 × as long as scutellum length, mostly smooth with a few longitudinal carinae on sides; Forewing stigma more rounded than in female, about 1.4 × as long as wide (Figure 28); upper part of stigmal vein elongate, 0.5 × as long as stigma length; uncus 0.7 × as long as upper part of stigmal vein; marginal vein 0.8 × as long as postmarginal vein. Propodeum with coarse longitudinal carinae, and short median carina in its upper part (Figure 27). Gaster conspicuously petiolate (Figure 23). Genitalia with rather small aedeagus, its part above digitus only 1.2 × as long as digitus length; digitus with only 2 teeth (Figure 29).

Variation. The transverse brown band at the anterior part of mid-lobe of mesoscutum is less marked in female paratypes. In males, the lateral black-brown spots could be absent on T5-T7.

Host plants.

Helinus integrifolius ( Rhamnaceae ). Probably a seed feeder, based on its place in the molecular phylogeny of Megastigmus spp. (Figure 14). Nevertheless we only sequenced one specimen and it would be necessary to analyze other samples in order to clarify the phylogenetic position, which appeared to vary depending on the marker.

Distribution.

Known only from the Matthews Range, Kenya where it was observed to emerge from 9.8 % of the collected fruits (Table 3).

Etymology.

Named after its host plant.

Diagnosis and comments.

This is the only species of Megastigmus found to date to emerge from fruits of the Rhamnaceae . Females are easily distinguished from those of other species present in the region by the very small ovipositor associated with an orange body colour. Genitalic characters differentiate males Megastigmus helinae by the presence of only two teeth on the digitus whereas the other species bear three teeth except Megastigmus icipeensis but the phallobase of the latter species is less elongate (Figure 74).