Ptiolina obscura (Fallén, 1814)

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

Ptiolina obscura (Fallén, 1814)

( Figs 7–8 )

MATERIAL EXAMINED: Belgium, Brussels-Capital Region: Auderghem, Jardin botanique Jean Massart, 1 female, 21–28 May 2015, MT2 ; 1 male, 28 May–4 June 2015, MT1 ; 1 male, 1 female, 4–10 June 2015, MT1 ; 1 female, 17–26 June 2015, MT1 (leg. A. Drumont & H. Raemdonck) .

ADDITIONAL OBSERVATIONS: 1 female, 3–9 June 2016, MT2 ; 1 female, 24 May – 1 June 2017, MT2 ; 1 male, 4 females, 24 May – 1 June 2017, MT4 (leg. A. Drumont & H. Raemdonck) .

A few more specimens of this very rare species were found in the years following the first sampling at the Garden, and thus examined and incorporated in the study. The adult flies were active from late May to late June and the flight period was about 1 month. Females were dominant.

COMMENTS

In his survey of the Belgian Rhagionidae KRIZELJ (1971) reports P. obscura as the single species occurring in Belgium and he cites it from Dave in the province Namur and from Vieuxville (Sy) in the province Luxembourg. The specimen from Dave that KRIZELJ possibly

saw was a heavily moulded female in the collections of RBINS bearing the label Dave 20.06.77 H. Donckier. Identified and labelled as Ptiolina nigra ? v.d. Wulp & Gobert det. Coucke rev. However, this very old specimen from 1877 was a female Symphoromyia immaculata Meigen, 1804 as could be seen from the large reniform third antennal segment.

The record from Sy that KRIZELJ maybe saw was a female, Sy, (prov. Liège) 24.VI.1933, M. Goetgebuer leg. (coll. RBINS). The following characters were observed: frons with eyes widely separated; squama with pale hairs (probably). Face entirely covered with hairs in middle as well as at sides (half as long as third antennal segment). First antennal segment short, half as long as second segment, the apical fine bristles are a little longer than the first segment. Mesonotum grey dusted lacking stripes. Discal cell long, about 4.5× as long as wide ( Fig. 7 ).

The collections of RBINS harbour also 1 male from Herbeumont (Prov. Luxembourg), 25– 8.VI.1952. M. Bequaert leg. (coll. RBINS) that appears to be correctly identified as P. obscura .

A male, Lixhe (prov. Liège) 1.VI.1947, M. Bequaert leg. (RBINS), identified as Ptiolina nigra was instead a Symphoromyia immaculata Meigen, 1804 .

STUBBS & DRAKE (2014) warn in their key to the species of Britain about the considerable uncertainties in the identification of the species of this genus. Indeed, there is a lot of confusion about a number of characters that have been mixed or misinterpreted such as e.g. the colour of the hairs on the squamae or the presence of bristling or the hairs on the face. In addition, there is a sexual dimorphism between males and females and at least in P. ptiolina the discal cell in

males is shorter than in females and cannot be used at the moment to differentiate between species because we are not aware of the characters in all the European species. Finally, there is no comprehensive study of the male terminalia available.

Figures

Fig. 7. Ptiolina obscura (Fallén, 1814), male habitus. © Camille Locatelli.

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