Plecia hadrosoma Hardy & Takahashi, 1960

Sutou, Mitsuaki, 2006, Immature stages of three Japanese species of the genus Plecia Wiedemann (Diptera: Bibionidae), Zootaxa 1223, pp. 1-18 : 11-13

Plecia hadrosoma Hardy & Takahashi, 1960

Description

Egg: Shiny brown, with smooth surface, 0.68–0.73 mm long (n = 20).

Final­instar larva: Genae with 6 setae anteriorly and 16 sensory pits dorsally including 8 sensory pits along ecdysial suture ( Fig. 5 D: 4–7). Frontal apotome with 2 setae and 4 sensory pits ( Fig. 5 D: 1–3). Clypeus with 4 setae and 6 sensory pits dorsally ( Fig. 5 D). Labrum with 2 small papillae and 2 sensory pits dorsally, about 6 small papillae and fine setae on its anterior membranous part ( Fig. 5 D). Epipharynx ( Fig. 5 E) with many fine setae, small conical processes, 2 rows of denticles, 8 small papillae and 4 sensory pits. Mandible ( Figs. 5 F, G) with 3 blunt teeth (teeth may be rather worn by feeding activity) bearing 3 setae and 2 dorsal sensory pits, well­developed prostheca attached inside. Cardo with 3 setae and sensory pit ventrally ( Fig. 5 J). Galeolacinia nearly trapezoidal in shape, with conical projection anteriorly ( Figs. 5 I, J); dorsal surface with fine setae, row of spinules, small digitiform process, and 6–7 sensory pits ( Fig. 5 I); ventral surface with 2 setae and row of denticles anteriorly ( Fig. 5 J). Stipes composed of 3 parts: proximal isolated appendage, middle sclerite with ventral sensory pit and dorsal U­shaped invagination, and distal membranous portion with some spinules, sensory pit, and seta ( Figs. 5 I, J). Maxillary palpus with sensory pit and 10–12 apical papillae, one of which is larger than others ( Fig. 5 J). Central membranous area of labium with 12 small papillae and fine setae on its anterior margin ( Fig. 5 H). Hypopharynx nearly elliptical in shape with some pubescence ( Fig. 5 H). Body dark brown, arrangement of processes as shown in Table 1 a. Plate­like ventral swelling of prothorax ( Fig. 5 B) with 5 processes. Body cuticle covered with many spinules ( Fig. 5 C). Width of head capsule 0.90–1.12 mm (mean ± SD = 1.02 ± 0.07 mm, n = 34; Fig. 7 b); Body length approximately 17–19 mm (measured from exuviae).

a

T1 T2 T3 A1 A2 A3 A4 A5 A6 A7 A8 A9

2/4/0 2/4/2 2/4/2 2/4/2 2/4/2 2/4/2 2/4/2 2/4/2 2/4/2 0/2/0

P. adiastola 18 4 6 6 6 6 6 6 6 6 4 12

2/4/0 2/4/0 4/4/2 4/4/2 4/4/2 4/4/2 4/4/2 4/4/2 4/4/0 4/4/0

2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 0/2/0

P. membranifera 18 4 4 4 4 4 4 4 4 4 2 8

2/4/0 2/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0

2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 2/4/0 0/2/0

P. hadrosoma 18 4 4 4 4 4 4 4 4 4 4 8

2/4/0 2/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0 4/4/0

Figures

FIGURE 5. Plecia hadrosoma, final­instar larva. A, habitus, lateral view. B, plate­like ventral swelling of prothorax. C, spinules on dorsum of fourth abdominal segment. D, head, dorsal view. E, epipharynx. F, right mandible, dorsal view. G, right mandible, inner view. H, labium and hypopharynx, ventral view. I, left maxilla, dorsal view. J, left maxilla, ventral view. See Fig. 1 for abbreviations. Scales: D, 0.5 mm. C, E – J, 0.1 mm.

FIGURE 7. Width of head capsule of final­instar larva. a: P. adiastola; larvae were collected from several locations. b: P. hadrosoma; larval exuviae were collected from a cluster of pupae. Two peaks in b indicate that the size difference between males and females (males <females) is apparent in the final­instar larva.