Botanophila helviana

Michelsen, Verner, 2009, Revision of the Botanophila helviana species group (Diptera: Anthomyiidae) in Europe, Zootaxa 2108, pp. 45-61 : 46-47

The Botanophila helviana species group

Diagnosis. Very small to small (wing length <5mm), blackish anthomyiids. Head sexually dimorphic. Mouthparts extended and slender; clypeus and prementum with sparse dusting, rather shiny black; small labella ( Fig. 3 ) with single row of rod-shaped teeth with blunt apices. Prealar seta long. Mid tibia without avseta; hind tibia with 3(–4) pd-setae, without apical pv-seta. Male terminalia: Cerci forming a square plate with 1–3 short, pointed prongs mid-distally; surstyli short, slender, barely incised at apex; pregonite small, firmly connected to the hypandrium, bearing two large, foliaceous setae; distiphallus short, largely membranous. Female oviscapt long and bulky with hind part of segment VI permanently exposed; hind marginal setae abundant on segment VI, but replaced by short setulae on segments VII and VIII; tergites VII and VIII consisting of paired, longitudinal struts, sternite VII incompletely divided along midline; cerci short, moderately depressed; setation relatively coarse and abundant on terminal sclerites.

Description. Size. Small, wing length 2.8–4.9mm.

Male. Upper part of frons with narrow, subcontiguous parafrontals; frontal setae and setulae reaching above middle of frons, followed by pair of interfrontal setae; orbital setulae absent. Face short, downwards concave with forwardly produced lower margin at level with or extended very slightly beyond frontoparafacial angle; no facial ridge between antennal sockets. Lower occiput dilated; gena in lateral aspect moderately to very narrow. Antennal postpedicel short, apically rounded; arista short-pubescent. Proboscis extended, with slender haustellum and small labella; prestomal teeth ( Fig. 3 ) peculiar, consisting of a single row of slender, blunt-tipped, dark rods. Clypeus shiny black, only with a little dusting on basal part. Prementum in part shiny black or at least darkly subshining through sparse dusting. Mesonotum uniformly dark-coloured or with three darker stripes visible in oblique posterior aspects. Presutural acrostichals setulose apart from more or less distinctly enlarged median pair. Prealar seta about same length as posterior notopleural seta. Proepisternals 2; proepimerals 1–8 setae and setulae. Katepisternals 1 + 2, lower posterior seta about two-thirds as long as upper posterior seta. Vein C without setulae ventrally or between two anterior rows of alternating spinules and setulae. Lower calypter about two-thirds as long as upper calypter. Fore tibia with 0 ad- and 0–2 hair-like p-setae. Mid femur on subbasal half with some av-setae barely longer than femoral depth and several long, fine pv-setae on basal half; mid tibia with 0 av-, 1 ad-, (1–)2 pd- and (0–)2 psetae. Hind femur with long av-setae on distal half, pv-setae short to absent apart from a few near apex; hind tibia with 2–3 av-, 4 ad- and 3(–4) strong pd-setae, often even with some short and fine p-setae on middle third, but without apical pv-seta. Abdomen depressed even on caudal part, with a dark mid-dorsal stripe and anterior bands to tergites III–V visible in oblique posterior aspects; weak hind marginal setae but no discal setae present on tergites III–V; tergite VI well exposed, bare (exceptionally with one or two setulae). Shape and setation of sternite V ( Fig. 4 ) unremarkable. Structure of cerci ( Fig. 5 ), surstylus ( Fig. 6 ), and pregonite ( Fig. 7 ) highly diagnostic for the species group.

Female. Apart from sexual differences different from male sex as follows: Broad frontal vitta anteriorly to varying extent orange to orange-brown. Thorax tends to be lighter greyish coloured, on mesonotum with 3 narrow dark grey or brownish stripes faintly visible from certain oblique aspects. Abdomen, except in B. helviana , with a thin to very thin layer of greyish to dark brownish dusting giving it an overall shiny black appearance; a mid-dorsal darker stripe is not apparent. Parafrontals on upper half with 3–4 pairs of orbital setae. Lower posterior katepisternal seta less than half as long as upper posterior seta. Fore tibia with 1(–2) strong ad-seta. Mid femur with only 1–3 short av- and pv-setae on basal half. Female oviscapt ( Figs. 8–10 ) long and bulky, when retracted posterior half of segment VI tends to be protruding from tip of preabdomen. Shape and setation of various parts of oviscapt possess species-diagnostic differences but also an overall similarity that separates the species group from other congeneric species and species groups.

Adult and larval biology. The adults of the Botanophila helviana species group are anthophilous, visiting flowering Asteraceae , Ranunculus , Dryas and others according to my field observations. They obviously obtain both nectar and pollen, as dissections of male and female abdomens for identification purposes regularly revealed pollen grains as a significant part of the gut contents. The peculiar structure of the prestomal teeth forming a single row of longish and slender, soft-tipped rods ( Fig. 3 ) may conceivably improve their ability to gather pollen grains from the anthers. A similar but even more excessive specialization of the prestomal teeth is known only from the globeflower anthomyiids currently assigned to genus Chiastocheta Pokorny (see Pellmyr 1992, fig. 4). These flies also supplement their diet of nectar with pollen, but exclusively from globeflower ( Trollius spp.).

Larval habits are practically unknown for all species of the Botanophila helviana species group. However, preliminary observations suggest that the larvae probably feed on developing achenes of buttercups ( Ranunculus spp.): At an excursion to a Danish locality (Høvblege, Møn) on June 25 1999 I collected 2 males and 1 female of Botanophila helviana on flowers of Creeping buttercup ( Ranunculus repens L.). I revisited Høvblege on June 22 2003 and brought a sample of buttercup flowers back to the lab for a closer examination. On the developing seed head of a single flower of R. repens I found an egg ( Fig. 1 ) that credibly belongs to B. helviana . It was yellowish white, ca. 1mm long, with a near-smooth chorion, i.e., without dorsal hatching pleats or a distinct pattern of fine hexagonal ridges. Dissection of a pregnant female of B. saliciphila disclosed the same kind of egg ( Fig. 2 ), ca. 0.9mm long.

Monophyly and relationships. The Botanophila helviana species group as presently delimited, i.e. excluding B. truncata ( Fan 1988) , is strongly supported as monophyletic on evidence of several shared characteristics in the male and female terminalia and the prestomal teeth (see above).

It is presently both difficult and premature to speculate about closest relationships of the B. helviana species group, because the genus Botanophila Lioy is so diverse, species-rich and still not fully satisfactorily delimited. On top of this, a thorough revision of the very rich Nearctic fauna (G.C.D. Griffiths in prep.) is still pending.

Figures

FIGURES 1 – 7. Botanophila spp. 1. Seed head of Ranunculus repens L. with supposed egg of B. helviana (arrow). 2. Uterine egg, B. saliciphila. 3. Left labellum, B. kitadakeana, female. 4. Male sternite V, B. helviana. 5, 6. Hypopygium in caudal and lateral aspects, B. miniatura. 7. Gonites, phallus (with ejaculatory apodeme) and phallapodeme in lateral aspect, phallus in anterior aspect, B. peristeriana. Scale bar = 1.0 mm (1); 0.25 mm (2); 0.1 mm (3 – 7).

FIGURES 8 – 10. Botanophila saliciphila, oviscapt in dorsal, lateral and ventral aspects. Scale bar = 0.25 mm.