Sylvenomyia Mamaev & Zaitzev 1998

Penttinen, Jouni & Jaschhof, Mathias, 2009, On the systematics of Sylvenomyia Mamaev & Zaitzev (Diptera, Cecidomyiidae, “ Porricondylinae ”), with the description of a new species from Finland, Zootaxa 2032, pp. 48-54 : 49-50

Genus Sylvenomyia Mamaev & Zaitzev 1998

Mamaev & Zaitzev 1998: 211.

Type species: Sylvenomyia sueciae Mamaev & Zaitzev 1998 [= Chastomera spinigera Spungis 1985 ].

Diagnosis. The strong anterior portion of C (antC) extends clearly beyond R5 and is followed by a costal break; M and CuA1 are absent ( Fig. 1 A). The antennae in males have 11 flagellomeres; the flagellomere nodes bear crenulate whorls of sensory hairs and hair-shaped translucent sensilla (Fig. 2A). The gonostylus bears a strong apical claw ( Figs 1 B, 2B, C). The simple, small tegmen is largely membranous and of broadconical shape ( Figs 1 D, 2C). Females and preimaginal stages of Sylvenomyia spp. are unknown.

Description. Head. Occiput with short setae. Postocular bristles absent. One pair of large top setae (see Panelius 1965). Postfrons convex, bilobate, asetose. Prefrons large, asetose. Eye bridge up to 4 ommatidia long. Remnants of larval stemmata not discernible. Antennal scape and pedicel subequal in size; scape setose ventrally; pedicel asetose; 11 flagellomeres, the 2 apical flagellomere fused; flagellomere nodes longer than necks, barrel-shaped, fully covered with microtrichia, 1 whorl of basal setae, 1 complete and 1–2 incomplete crenulate whorls of long sensory hairs, several hair-shaped translucent sensilla distally (Fig. 2A). Clypeus smaller than prefrons, projecting in lateral profile, with large setae. Maxillary palpus long, 4-segmented, setae long and curved or short and straight; first segment with hair-shaped translucent sensilla.

Thorax. Pronotum asetose. Scutum with sparse dorsocentral and lateral setae. Pleural setae absent. A portion in between laterotergite and mediotergite covered with strikingly large microtrichia. Wing ( Fig. 1 A). Comparatively short and broad, about as long as body. Membrane covered with microtrichia and setae. AntC extending clearly beyond R5, followed by break; Sc long, evanescent apically; h absent; Rs with vertical rather than horizontal inclination; r-m + m-cu horizontal, in juxtaposition with R5; M and CuA1 absent; CuA2 slightly curved, weak or evanescent apically; CuP short, running very close to CuA2; 1 branch of A present, albeit short; dorsal setae present on Sc basally, stem vein, R, R1, R5, and CuA2; ventral setae absent. Pattern of sensory buds: R1, 2 distal; R5, 1 basal, 2 distal; further 1 mesal sensory bud on Sc. Halter comparatively short, stem and node subequal in length. Legs. Foreleg slightly longer than body, femur shorter than tibia, tibia shorter than tarsus; first segment of foretarsus 1/3 the length of second segment, with short, blunt apical projection. Pretarsal claws slightly curved, with minute teeth at midlength. Empodia vestigial.

Abdomen. All sclerites covered sparsely with large setae. Pattern of tergal plaques not fully resolved, presumably 0/2/2/1/1/1/1/0. Terminalia ( Figs 1 B, C, 2B–D). St9 not traceble. Tg9 subtrapezoid, with straight apical margin. Gonocoxites with deep ventral emargination extending beyond midlength; ventral bridge membranous; posterior portion of gonocoxal apodeme (postGA) long, extending to ventrobasal gonocoxal margin; anterior portion of gonocoxal apodeme (antGA) moderately long; dorsal transverse bridge unsclerotized. Gonostylus slightly tapered towards apex, with strong, multipointed apical claw. Ejaculatory apodeme as long as gonocoxites, strongly sclerotized, with membranous, tulip-shaped cap apically. Ducts of accessory glands distinctive. Tegmen small, largely membranous, broad-conical, rounded apically, ventrolateral margins serrate or with scaly surface, apex weak, parameral apodemes directed ventroanteriorly. St10 weak, bilobate, pubescent, asetose. Cerci not or not much extending beyond tg9, setose.

Systematic position. Mamaev and Zaitzev (1998) classified Sylvenomyia with the Winnertziini , a decision presumably influenced by the wing venation, the presence in males of less than 14 flagellomeres, and the simple, hair-shaped antennal sensilla. On first sight, this classification seems plausible and supported by further features, such as the absence of pleurothoracal setae and the Winnertzia -like male terminalia, i.e. the gonostyli equipped with an apical claw and the parameres fused to form a simple, membranous tegmen. However, several other features of Sylvenomyia are not known from Winnertzia or other Winnertziini : an asetose pedicel, crenulate whorls of sensory hairs, hair-shaped translucent sensilla on the maxillary palpus, and an asetose pronotum. Also, the first tarsal segments in Sylvenomyia are longer than those in the other porricondylines known to us, with the exception of some Heteropezini. A unique feature of Sylvenomyia is antC extends beyond R5, whereas the apices of these two veins are confluent in the other porricondylines with a costal break. In Heteropezini, which lack the costal break, the costa is gradually narrowed near the apex of the wing. Altogether, there is little support for Sylvenomyia being correctly placed among the Winnertziini . An affiliation of Sylvenomyia to the Heteropezini would also be inappropriate, because the heteropezine imago is variously degenerated ( Wyatt 1967), unlike the imago in Sylvenomyia . The Diallactini, with 14 male flagellomeres, cannot accommodate Sylvenomyia either. We do not see a better solution than leaving Sylvenomyia unplaced to any tribe for the time being.

As regards the Cecidomyiidae other than “ Porricondylinae ”, sylvenomyias bear an uncanny resemblance to Lestremiinae . If the first tarsal segments were longer than the second segments – the feature that unfailingly separates Lestremiinae from “ Porricondylinae ” and Cecidomyiinae – then sylvenomyias could be considered lestremiines. A venation pattern similar to that in Sylvenomyia is known from some unusual lestremiines classified with the tribe Strobliellini . The terminalia of Sylvenomyia males correspond largely with those in some species of the Catochini , another lestremiine tribe. Last but not least, crenulate whorls of sensory hairs, the presence of which is exceptional among porricondylines, is a feature typical of lestremiines. We do not stress these similarities to suggest a close interrelationship between Sylvenomyia and certain Lestremiinae but to support our assumption that Sylvenomyia belongs to a basal porricondyline lineage distinct from other such lineages, such as the Diallactini, Winnertziini and Heteropezini.

Figures

FIGURE 1. Morphology of Sylvenomyia spp. A: Wing of S. fennica sp. n., dorsal view (holotype, 0.5 mm). B: Male terminalia of S. spinigera, ventral view (specimen from Lieksa, 0.05 mm). C: Ejaculatory apodeme and tegmen of S. s pinigera, ventral view (specimen from Kondopoga, 0.05 mm). acgld = accessory gland duct, antC = anterior portion of costa, antGA = anterior portion of gonocoxal apodeme, cbr = costal break, cerc = cercus, dtrbr = dorsal transverse bridge, memcp = membranous cap, parap = parameral apodeme, postC = posterior portion of costa, postGA = posterior portion of gonocoxal apodeme, vgxbr = ventral gonocoxal bridge.