Piogaster punctulata Perkins, 1958

Figs 16, 17

Piogaster punctulata Perkins, 1958: 264.

Polysphincta pilosator Aubert, 1958: 79; Synonymized with P. pilosator by Aubert (1967); synonymy not adopted by Fitton (1976), Fitton et al. (1988), Yu and Horstmann (1997), Shaw (2006), Broad (2016) and the current study.

Diagnosis.

The female of Piogaster punctulata can be distinguished from all female congeners by possession of the combination of the following: 1) mesopleuron polished with shallow punctures (Fig. 17 A) (polished and impunctate to weakly coriaceous, matte and rugulose to rugose, or matte and granulate to pustulate in all other species); 2) mesoscutum subpolished and punctate (Fig. 16 E) (polished and impunctate, mat and granulate, matte and rugose, or matte and punctate in all other species); and 3) frons matte, granulate laterally, granulations become transversely strigose laterally (Fig. 16 D) (polished and smooth, coriaceous, punctate, matte and granulate (not transversely strigose laterally), rugulose to rugose, rugose punctate or punctate in other species).

Redescription.

Adult. Female. Body length 4.8 mm. FW length 4.1 mm. Head. Antennae with 22 flagellomeres. Clypeus 1.5 × as wide as high, polished with sparse punctures, with yellow-white setae (Fig. 16 C). Face matte, rugose-punctate, with moderately dense medium length yellow setae (Fig. 16 C). Frons matte, granulate laterally, granulations become transversely strigose laterally, with dense short light brown setae (Fig. 16 D). Vertex matte and densely punctate, punctures small and touching, with dense medium length yellow setae (Fig. 16 D). Occipital carina complete. MSL 0.7 × as long as BWM. OOD 1.5 × as long as LOD. Mesosoma. Pronotum with epomia absent; subpolished, coarsely, densely punctate dorsally, rugose-punctate anteromedially, with dense medium length yellow setae. Mesoscutum subpolished, densely punctate, dense medium length light brown setae (Fig. 16 E). Scutellum punctate, punctures nearly touching, with dense medium length white-brown setae (Fig. 16 E). Mesopleuron polished, shallowly punctate with less than width of a puncture between punctures, rugose-punctate dorsal to mesopleural fovea, with moderately dense long white-brown setae (Fig. 17 A). Metapleuron subpolished, densely, deeply punctate, with dense long light brown setae (Fig. 17 B). Propodeum subpolished, coarsely deeply punctate, medially longitudinally rugose-punctate, with dense long white setae (Fig. 17 C). Propodeum with pleural carina weak but complete (Fig. 17 B); lateral longitudinal carina present in posterior 0.3, all other propodeal carina absent. Wings. Fore wing. Vein Rs + M without ramellus extending into cell 1 M + 1 R 1. Vein 2 rs-m 0.6 × as long as M between 2 rs-m and 2 m-cu. Vein 2 m-cu not thickened or angulate between bullae. Hind wing. Vein 1 / Cu & cu-a inclivous and strongly angled apically (Fig. 17 D), 2 / Cu intercepting in lower 0.3, 2 / Cu basally tubular then nebulous. Metasoma. T 1 subpolished, densely punctate, punctures nearly touching, lateroposteriorly punctate reticulate with dense medium length white setae. T 1 median dorsal carina indistinct to absent; dorsolateral carinae present to spiracle, absent (rounded) just posterior to spiracle, present posteriorly (Fig. 17 B). T 2 – T 6 subpolished, coarsely, densely punctate with anterior and medial areas punctate reticulate, with dense short white setae (Fig. 17 E). T 7 polished, shallowly punctate, with moderately dense short white setae. T 8 polished, smooth with sparse short white setae (Fig. 17 E). Tergites without grooves or tubercles. Ovipositor sheaths 0.8 × as long as hind tibia (Fig. 15 A). Colour. Clypeus, face, frons, gena and occiput predominantly medium brown (Figs 16 A, 16 C, 16 D). Vertex medium brown with faint, thin linear brown-orange mark extending from posterior 0.3 of eye, roughly longitudinally to level of middle of lateral ocellus. Mandible red-brown with medial black transverse stripe. Maxillary and labial palps dark brown. Antenna brown, basal 12 flagellomeres yellow ventrally. Pronotum brown-orange on dorsal 0.7, brown on ventral 0.3. Tegula dark brown (Fig. 16 A). Mesoscutum brown-black, brown-orange anteriorly (Fig. 16 E). Scutellum, post-scutellum and axillary troughs dark brown-black. Mesopleuron dark brown-black, brown-orange anteriorly (Fig. 17 A). Metapleuron black (Fig. 17 B). Propodeum uniformly black (Fig. 17 C). Wings hyaline, veins light brown to translucent (Fig. 17 D). Legs with coxae dark brown, remainder of legs white with the following dark brown: dorsal surface of trochanters, longitudinal stripe on dorsal and / or ventral surface of femora and / or tibiae, dorsal of tarsi (Fig. 16 A). Metasomal tergites brown, T 5–7 darker than T 1 – T 4 (Figs 16 A, 17 E), T 8 brown-orange medially. Ovipositor sheath brown.

Male. Unknown. Perkins (1958) described a specimen from Germany he said was possibly a male P. punctulata, but we were unable to locate this specimen (see Comments). The description of this specimen is consistent with all other European male Piogaster specimens we examined.

Distribution.

Fig. 28. England.

Biology.

Unknown.

Material examined.

Holotype. England • ♀; Surrey, Horsley; 11. vi. 1952; D. M. S. Perkins; Hym. 3 b. 2024; [NHMUK].

Comments.

The holotype specimen is the only female of P. punctulata known to us. Considering that the type locality is in a very well-collected part of the world in close proximity to NHMUK, this is surprising, suggesting that the species may be very rare. Alternatively, the holotype of P. punctulata could be a variant of P. pilosator with an exceptionally polished mesopleuron with reduced punctation and lacking the extensive rugulose / rugose sculpture of P. pilosator. This idea was considered by Perkins (1958) who said that P. punctulata “ may prove to be only a form of P. rugosa ” which is now a junior synonym of P. pilosator. Piogaster punctulata was synonymized under P. pilosator by Aubert (1967), but there was uncertainty in this synonymy and it was not adopted by subsequent authors (Fitton 1976; Fitton et al. 1988; Yu and Horstmann 1997; Shaw 2006; Broad 2016). The hypothesis that sculpture could have intraspecific variation is supported by observed variation in the sculpture of other species of Piogaster, for example, the propodeum of P. albina can be moderately rugose to almost completely smooth (compare Figs 5 D, 6 A). However, we have examined or seen photos of more than 30 females of P. pilosator from all over continental Europe (Fig. 30) and none of them have highly polished mesopleura (Figs 14 B, 15) and all of them have extensive rugosity that differs greatly from the mostly smooth sculpture of the holotype of P. punctulata (Fig. 17 A). For now, we maintain P. punctulata as a distinct species and hope additional material will be collected to clarify its status.

As noted above, we were unable to locate the male Piogaster specimen that Perkins (1958) tentatively associated with the female of P. punctulata. The only information provided about this specimen was that it was collected in Germany and is part of the Ruthe collection. Johann Friedrich Ruthe’s (1778–1860) collection was acquired by the NHMUK upon his death, as indicated in his eulogy (Kraatz 1860). A female Piogaster specimen from the Ruthe collection is present in NHMUK, designated by Perkins (1958) as the holotype of P. albina, but the male Piogaster punctulata could not be located. Other males of P. punctulata have been mentioned in the literature (Fitton et al. 1988; Shaw 2006). We examined the male from Fitton et al. (1988) and the Santon Downham specimen from Shaw (2006). Both of these males most closely resemble the holotype of P. punctulata in that they have a punctate mesoscutum and a relatively polished, impunctate mesopleuron. However, all European males share these sculptural characters (Figs 24, 25), and we were unable to find characters that can be used to associate male specimens to their female counterparts in Europe.