Ptiolina species, 1842

Grootaert, Patrick, Raemdonck, Hugo & O. D., Alain Drumont, 2020, The Rhagionidae or Snipeflies of the Botanical Garden Jean Massart (Brussels-Capital Region, Belgium) with notes on the identity of the rare European species Archicera avarorum Szilády, 1934 and Ptiolina obscura (Fallén, 1814) (Diptera: Rhagionidae), Belgian Journal of Entomology 104, pp. 1-18 : 1-18

Key to the Ptiolina species supposed to occur in We stern Europe, excluding the boreal and subboreal species (copied and adapted from STUBBS & DRAKE, 2014)

1. First antennal segment twice as long as second antennal segment (both segments covered in hairs longer than width of segments). Male with face bare centrally, the hairs on the strip bordering the eyes should be ignored; female face with short hairs .............................. P. nigra

- First and second antennal segments more or less equal in length (hairs on face present or absent) ....................................................................................................................................... 2

2. Face with long hairs centrally (hairs on the wide hairy strip next to the eyes should be ignored). (Hairs on first and second antennal segment moderately long) ................... P. nigrina

- Face bare centrally (male) or sparsely hairy (female) ............................................................. 3

3. Female frons dull. Squamae in both sexes with a fringe of black hairs (careful since they can appear yellowish in some lights). (Wings darkened) ................................................. P. obscura

- Female frons polished. Squamae in both sexed with a fringe of pale hairs ................. P. nitida

COMMENTS

The identification of Ptiolina species remains uncertain because of doubts on the reliability of characters: variability of the colour of the fringe of bristles on the squama from pale to black, length of the discal cell and we could not find illustrations of the male terminalia from the various species. Nevertheless, we presume that all the Ptiolina found at the Botanical Garden Jean Massart represent P. obscura and the illustration of the male terminalia might provide a further reference to the identification of the species ( Fig. 8 ).

In his key to the Rhagionidae VAN DER GOOT (1985) mentions that no Ptiolina species are known from Belgium and that P. nigrina Wahlberg is the only species known from the Netherlands. BEUK et al. (in litt.) doubt this however and state that only P. obscura is present in the Netherlands.

In her revision of the northern Palaearctic Ptiolina, NARTHCHUK (1995) states that Ptiolina obscura (Fallén, 1814) has darkened wings, a black fringe on the wing squamae and the face is bare or with sparse hairs. The two basal segments of the antennae are equal in length, with abundant short bristles but no long hairs. The antennal flagellomere is not longer than 1.5× as long as wide. However, we are not sure about the precise meaning of the latter (third antennal segment). In male all femora and hind tibia have long hairs. It is clear that not all these characters correspond to our specimens. Unfortunately, no illustrations of the male terminalia or other structures are provided and a revision coupled to genetic barcodes is needed to elucidate this problem.

Figures

Fig. 8. Ptiolina obscura (Fallén, 1814) Male terminalia. A. Ventral view; B. Dorsal view. Scale 0.1 mm. © Patrick Grootaert.