Plecia adiastola Hardy & Takahashi 1960
Creators: name: Sutou, Mitsuaki
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Bibionidae
Plecia
Plecia adiastola

description: Plecia adiastola Hardy & Takahashi, 1960
Description
Egg: Shiny brown with smooth surface (Fig. 1 A), 0.53–0.65 mm long (n = 20).
Final­instar larva: Genae with 6 setae anteriorly and 18 sensory pits dorsally including 8 sensory pits along posterior stem of ecdysial suture (Fig. 1 G: 4–7). Frontal apotome with 2 setae anteriorly, 2 minute setae posteriorly, and 2 sensory pits between them (Fig. 1 G: 1–3). Clypeus with 4 setae and 6 sensory pits dorsally (Fig. 1 G). Labrum with 2 minute setae and 2 sensory pits dorsally, about 10 small papillae and fine setae on its anterior membranous part (Fig. 1 G). Epipharynx (Fig. 1 H) with many fine setae, small conical processes, 8 differentiated small papillae and 4 sensory pits. Mandible (Figs. 1 I, J) with 3 large and 2 small teeth, well­developed prostheca attached inside, 3 setae and 2 dorsal sensory pits on its basal half. Cardo with 3 setae and sensory pit ventrally (Fig. 1 M). Galeolacinia nearly quadrilateral in shape, with conical projection and 2–3 small papillae on anterior margin (Figs. 1 L, M); dorsal surface with many fine setae, spinules, and 5–7 sensory pits (Fig. 1 L); ventral surface with 1 seta (Fig. 1 M). Stipes composed of 3 parts: proximal isolated appendage, middle sclerite with seta and sensory pit, and distal membranous ring with sensory pit (Fig. 1 M). Maxillary palpus with sensory pit and 11–13 apical papillae, 1 or 2 of which slightly longer than others (Fig. 1 M). Central membranous area of labium with 12–14 small papillae and fine setae on its anterior margin (Fig. 1 K). Hypopharynx nearly wing­like in shape with some pubescence (Fig. 1 K). Body dark brown, arrangement of processes as shown in Table 1 a, but following deformations were found in some specimens: number of lateral processes of T3 only 4, posterior row of ventral processes of A1 and A2 absent. Plate­like ventral swelling of prothorax (Fig. 1 C) with 3 processes, central one smaller than lateral ones. Body cuticle covered with many spinules (Fig. 1 D). Width of head capsule 0.68–0.92 mm (mean ± SD = 0.78 ± 0.06 mm, n = 67; Fig. 7 a); Body length 11.7–16.7 mm (mean ± SD = 14.2 ± 1.5 mm, n = 66).
Pupa. Male (Figs. 2 A, B): Vertex uneven in frontal view; antenna arched, extending obliquely; maxillary palpus extending laterally; rostrum short. Extremities of hind legs reaching posterior margin of 2nd abdominal segment or anterior margin of 3rd abdominal segment. Arrangement of body processes as shown in Table 1 b, but venter of A3 with 2 setae in some specimens. Abdominal spiracles flat, not protruded from body surface. Body length 6.3–10.0 mm (mean ± SD = 8.5 ± 1.0 mm, n = 26). Female (Fig. 2 C): similar to male, but compound eye smaller, abdomen thicker than that of male. Body length 7.6–11.1 mm (mean ± SD = 9.5 ± 0.7 mm, n = 24).
Specimens examined
Egg: Laid by females reared from larvae or pupae collected on 29.III.1998 and 17.IV. 2001 in Tokiwadai, 35°28’N 139°35’E, 60 m alt., Hodogaya ward, Yokohama, Kanagawa Pref. and on 29.IV. 2000 in Mt. Inao, 31°07’N 130°53’E, 600 m alt., Sata, Kagoshima Pref. Final­instar larva: 14 examples, 6.V.2003, Mukaiyama, 38°14’N 140°52’E, 70 m alt., Taihaku ward, Sendai, Miyagi Pref.; 6 examples, 29.III.1998, 21 examples, 17.IV.2001, 18 examples (10 examples in NSMT), 5.XII.2002, 14 examples, 4.IV.2003, Tokiwadai, Yokohama; 5 examples, 9–10.III.2000, Shiroyama, 31°35’N 130°32’E, 60 m alt., Kagoshima, Kagoshima Pref. Pupa: 13♂, 14Ψ (5♂, 5Ψ in NSMT), reared from larvae collected on 6.V. 2003 in Mukaiyama, Sendai; 2♂, 2Ψ, 10.V.1998, Tokiwadai, Yokohama; 4♂, 5♂ and 3Ψ, reared from larvae collected on 29.III.1998 and 17.IV.2001 respectively in Tokiwadai, Yokohama; 3Ψ, reared from larvae collected on 9–10.III. 2000 in Shiroyama, Kagoshima; 3♂, 2Ψ, 29.IV.2000, Mt. Inao, Sata.
Ecological notes
The distribution of this species appears to be restricted to Japan. In the plains of central Japan, the adults emerge from mid­May to early June, and the final­instar larvae develop beyond the winter (univoltine). The larvae and pupae are usually gregarious in soil. The number of individuals in a single cluster ranged from 23 to 96 in the present study. The larvae of this species prefer damp soil in a forest, e.g., directly under rotting wood. According to Krivosheina (1998), the larvae of the closely related species P. thulinigra live in rotting wood at the final stage of decomposition in Far East Russia. Many males of P. adiastola were observed walking on piles of decayed wood trying to mate with females (29. V. 2000, Hachioji, Tokyo). Flight activity was rarely seen in this species, but several males were once observed flying during daylight hours (25–26. V. 2001, Yokohama).
description: Published as part of Sutou, Mitsuaki, 2006, Immature stages of three Japanese species of the genus Plecia Wiedemann (Diptera: Bibionidae), pp. 1-18 in Zootaxa 1223 on pages 5-6, DOI: 10.5281/zenodo.172619