Diplazon tetragonus

Diplazon tetragonus (Thunberg, 1822)

(Figs 37–40)

Ichneumon tetragonus Thunberg, 1822: 280.

See Yu et al. (2016) for complete details.

Diagnosis. Face covered with dense punctures. Antenna with 16–17 flagellomeres. Mesopleuron polished and covered with dense punctures except for on and below speculum (Fig. 39). Propodeal carinae complete. Metasoma polished and dorsoventrally depressed. Transverse impressions distinct on T I to T IV, but often indistinct on T VI. T I 0.90–1.12 × as long as maximum width in both sexes. T II 0.64–0.71 × as long as maximum width in both sexes. T II and T III rugulose but also covered with irregular punctures except for behind transverse impressions of T III largely smooth (Fig. 40). Face black except for a pair of longitudinal stripes along inner orbit yellow (Fig. 38). Scutellum yellow except for anterior part of scutellum black. Mesopleuron entirely black (Figs 37, 39). Coxae orange except for basal part of fore coxa blackish-orange (Fig. 37). Hind tibia is banded as “black-white-black” (Fig. 37). Metasoma entirely black.

Specimens examined. JAPAN: 1♀, Hokkaido, Furano City, Mt. Shimizuyama 29. IX –3. X. 1993, K. Suzuki leg. (NIAES); 2♀, Kanagawa Pref., Hadano City, Mt. Koubouyama 5. IV. 2007, K. Watanabe leg. (KPMNH); 1♀, ditto, 29. IV. 2007 (KPMNH). FRANCE: 1♀ (det. Klopfstein), Gallia F. J. Sichel leg. (NHRS). RUSSIA: 1♂ (det. Klopfstein), Kamtschatka (MT) (NHRS).

Distribution. Japan (Hokkaido, Honshu, and Kyushu); widely distributed in Holarctic and Oriental regions.

Bionomics.­­ A number of hoverfly species have been recorded as a host (See Yu et al. 2016 for detail), while no records are known from Japan.

Remarks. Balueva & Lee (2015) indicated that this species is one of the most common species of this genus, however, only four female specimens have been identified in Japan. Thus, this species appears to be rare in Japan.