Plecia hoffeinsorum Skartveit, 2009: 17-19

Skartveit, John, 2021, A new fossil species of the genus Bibio, with an update on bibionid flies from Baltic and Rovno amber (Diptera, Bibionidae), Deutsche Entomologische Zeitschrift 68 (1), pp. 81-99 : 81

Plecia hoffeinsorum Skartveit, 2009: 17-19 Figs 5 , 6 , 7 , 19 , 20 , 21 , 22 , 23

Plecia tenuicornis Skartveit, 2009: 20-22. Syn.n.

Type material.

Holotype (male) of Plecia hoffeinsorum SDEI Dip-00827 - CCHH#1448-2, preserved together with six conspecific males. Paratype (male) SDEI Dip-00843 - CCHH#1629-2. Holotype (male) of Plecia tenuicornis SDEI Dip-00828 - CCHH#1501-2. Paratypes (males): SDEI Dip-00837 - CCHH#335-2. SDEI Dip-00838 - CCHH#935-2. SDEI Dip-00839 - CCHH#1025-1. SDEI Dip-00840 - CCHH#1025-2. SDEI Dip-00841 - CCHH#1567-3. SDEI Dip-00843 - CCHH#1629-2 (Preserved together with holotype). Previously studied non-type, female, CCHH#1501-3.

New material, Baltic amber: males: JS-Baltic-004, in piece of amber 27 ×20× 6 mm, syninclusions: cecidomyiid midge, 2 phorid flies; JS-Baltic-005, in piece of amber 16 ×12× 4 mm. JS-Baltic-007, in piece of amber 22 ×13× 6 mm. Females: SDEI In 001701 (syninclusion with Sciarid midge); JS-Baltic-006, in piece of amber 13 ×7× 3 mm. Rovno amber, male: JS-Baltic-008, in rather large piece of amber 36 ×20× 15 mm, syninclusions: copious plant debris, possibly flower fragments.

The species was described based on seven male specimens preserved together in one piece of amber. The present specimens do show the male terminalia better than the type material, hence this is redecribed here, otherwise the external morphology is adequately described in the original descriptions of Plecia hoffeinsorum and Plecia tenuicornis ( Skartveit 2009: 17-22). The female of Plecia hoffeinsorum was described from a compression fossil from Grube Messel ( Skartveit and Wedmann 2016). The two species Plecia hoffeinsorum and Plecia tenuicornis were originally thought to have rather different male terminalia ( Skartveit 2009, figs 34, 35, 46, 47), however studying additional specimens suggests that the two “forms” are actually the same structure with the gonostylus fixed in different positions. As usual with Bibionidae the angle of view is quite critical when studying these structures.

Measurements, including new material.

Males: body length 4.5-5.2 mm (N = 4), thorax length 0.92-1.30 mm (N = 8), wing length 4.0- 5.2 mm (N = 6). Females: body length 4.5-4.6 mm (N = 2), thorax length 0.97-1.17 mm (N = 2), wing length 4.6 mm (N = 1). Wings as in Figs 19 , 20 , head as in Figs 21 , 22 .

Redescription of male terminalia

(Fig. 23 ). Hypopygium width 0.43 mm (N = 1), outline almost rectangular, slightly expanded apicad. Gonostylus 0.22 mm long, attached apically on gonocoxite, long and slender, straight, apically somewhat pointed, with numerous long, curvy setae. Epandrium rather small, rounded-rectangular, posterior edge sligthly convex. Gonocoxosternite apically with a short, blunt tooth on each side just mesal to gonostylus attachment, posterior edge slightly convex.

Figures

Figure 5. Plecia hoffeinsorum, male. JS-Baltic- 004. Photo: Marius Veta.

Figure 6. Plecia hoffeinsorum, female. JS-Baltic- 006. Photo: Marius Veta.

Figure 7. Plecia hoffeinsorum, male, Rovno amber. JS-Baltic- 008. Photo: Jonas Damzen.

Figure 19. Plecia hoffeinsorum, male, wing. Scale bar: 1 mm.

Figure 20. Plecia hoffeinsorum, female, wing. Scale bar: 1 mm.

Figure 21. Plecia hoffeinsorum, male, head and thorax. Scale bar: 1 mm.

Figure 22. Plecia hoffeinsorum, female, head and thorax. Scale bar: 1 mm.

Figure 23. Plecia hoffeinsorum, male, terminalia. Scale bar: 0.1 mm.