Monoctenus itoi Okutani, 1958

Hara, Hideho & Nagase, Hirohiko, 2023, The Japanese species of Monoctenus (Hymenoptera: Diprionidae), Zootaxa 5380 (6), pp. 541-561 : 550-552

publication ID	https://doi.org/ 10.11646/zootaxa.5380.6.3
publication LSID	lsid:zoobank.org:pub:AA915DFA-58B9-428D-AF5D-193E3295AB04
DOI	https://doi.org/10.5281/zenodo.10259703
persistent identifier	https://treatment.plazi.org/id/03B38786-FF9D-CD55-FF21-FC0BFC6A57D8
treatment provided by	Plazi
scientific name	Monoctenus itoi Okutani, 1958
status

Treatment

( Figs 2C2, D2 View FIGURE 2 , 5A 2a View FIGURE 2 , 6A 2a, B2a View FIGURE 2 , 7A1, B1, 8A 2 View FIGURE 2 , 10A 2b View FIGURE 2 , 11A1a, b, 15, 16)

Monoctenus itoi Okutani, 1958: 144 ; Togashi 1965: 253; Okutani 1967: 48; Smith 1975: 410; Okutani 1984: 24; Abe & Togashi 1989: 545; Togashi 2001: 42 (part, male); Taeger et al. 2010: 211; Yoshida 2006: 36; Yoshida 2010: 28; Hara 2019: 46; Hara 2020: 287 (part, male).

Additional description. Female. Length 6.9–8.6 mm. Figs 5A View FIGURE 5 2a View FIGURE 2 , 15A, B. Head capsule black, with supraclypeal area yellow red to red brown, anterior tentorial pit and its surroundings usually yellow red to red brown, clypeus often yellow red to red brown dorsomedially, and lateral furrow of postocellar area and its surroundings and dorsomedial part of occiput often yellow red to red brown ( Fig. 15E–H View FIGURE 15 ). Labrum black. Prepectus brown to black. Postspiracular sclerite black, sometimes partly yellow to brown. Mesepisternum and abdomen without pale parts respectively ( Fig. 5A View FIGURE 5 2a View FIGURE 2 , 15A, B).

Clypeus without median furrow; ventral edge widely concave ( Fig. 15G, H View FIGURE 15 ). Antenna with 19–21 antennomeres ( Fig. 7A View FIGURE 7 1 View FIGURE 1 ); flagellomere 6 in lateral view with breadth including serration 1.8–2.1 × dorsal length. Valvula 3 ( Figs 2C2, D2 View FIGURE 2 , 15I) in dorsal view tapering and with apex nearly pointed or narrowly rounded, in lateral view with apex narrowly rounded and dorsal edge nearly straight. Lance in lateral view with dorsal edge gently rounded at basal two-fifths and almost straight from middle to near apex ( Fig. 15J View FIGURE 15 ). Lancet with 10 annuli ( Figs 7B View FIGURE 7 1 View FIGURE 1 , 15K View FIGURE 15 ); length from ventral end of ctenidium 1 to apex 4.1–4.6 × breadth; ctenidia 1 and 2 converging dorsally; ctenidia 2–7 parallel, inclined anteriorly.

Male. Length 6.6–7.7 mm. Fig. 15C, D View FIGURE 15 ). Labrum dark brown to black ( Fig. 10A View FIGURE 10 2b View FIGURE 2 ). Pronotum black ( Fig. 11A View FIGURE 11 1a View FIGURE 1 ), often narrowly brown posterodorsally ( Fig. 11A View FIGURE 11 1b View FIGURE 1 ). Tegulae black, sometimes yellow laterally. Antenna with 25–30 rami (28–33 antennomeres). Subgenital plate in ventral view rounded apically. Genitalia Fig. 15L View FIGURE 15 ; in penis valve, paravalva with ventral edge roundly convex and inner sclerite narrow, broadest near apex ( Fig. 15M View FIGURE 15 ); valviceps 2.7–2.8 × as long as broad.

Immature stages. Early instar larva ( Fig. 16B View FIGURE 16 ): Head and thoracic legs black; trunk green yellow. Late instar larva ( Fig. 16C View FIGURE 16 ): 16–20 mm long; head brown yellow with black markings; thoracic legs black; trunk green. Probably final feeding instar larva ( Fig. 16D, E View FIGURE 16 ): As in late instar. Cocoon ( Fig. 15F View FIGURE 15 ): 10 mm long; brown; double-walled, with outer wall very loosely spun and inner wall tightly spun.

Material examined. Japan, Honshu : 1♀ 2♂, Kanagawa Pref, “Ôyama”, V. 1935, K. Sato ( Fig. 6B View FIGURE 6 2a View FIGURE 2 , 7B1, 15L, M) ; 1♀, Kanagawa Pref, Yokohama, Ngatsuda , 4. V. 1933, K. Sato ( Fig. 15F, H, K View FIGURE 15 ) ; 11♀ 10♂, Kanagawa Pref, Yokohama, Asahi Ward , Yasashi , 23. V. 2021, M. Ishii ( Fig. 7A View FIGURE 7 1 View FIGURE 1 ) ; 6♀, same locality, 26. V. 2022, H. Nagase, and their eggs ( Fig. 15A, B, J View FIGURE 15 , 16A View FIGURE 16 ) ; 7♀, same data but 26. V. 2023, and their progeny, eggs laid 28–31. V., hatched 10. VI., coc. 11. VII. ( Fig. 16B–F View FIGURE 16 ) ; 37♀ 30♂, Kanagawa Pref, Yokohama, Seya Ward , Seya , 25. V. – 1. VI. 2002, M. Ishii ( Figs 2C2, D2 View FIGURE 2 , 5A 2a View FIGURE 2 , 6A 2a View FIGURE 2 , 8A 2 View FIGURE 2 , 10A 2b View FIGURE 2 , 11A1a, b, 15C, D, E, G, I) ; 14♀ 1♂, same data but 25. V. 2004 ; 1♂, Hyogo Pref., Mt. Oginosen , 9. VII. 2012, T. Naito ( Fig. 10A View FIGURE 10 2a View FIGURE 2 , 11A 2b View FIGURE 2 ). Part of the specimens from Yokohama are deposited in Kanagawa Prefectural Museum of Natural History, Odawara .

Okutani (1958) described this species based on two females and two males. In the National Museum of Nature and Science, Tsukuba, where Okutani’s collection is currently preserved, we did not find any of the type specimens .

Distribution. Japan (Honshu) ( Okutani 1958).

Host plant. Cupressaceae : Chamaecyparis obtusa (Siebold et Zucc.) Endl. ( Okutani 1967) , C. pisifera (Siebold et Zucc.) Endl. ( Okutani 1958) .

Life history. This sawfly is univoltine. The adults occur in May in the lowlands. Under rearing conditions, the females laid eggs individually inside one year old needles ( Fig. 16A View FIGURE 16 ); the early instar larvae ate current year needles, but the late instar larvae mainly ate old needles.

Remarks. Specimens from Kanagawa Prefecture, which include a good number of female and male specimens collected together, show no distinct differences between them, so they can be safely considered to be the same species. They agree with the original description of M. itoi better than descriptions of other similar species, M. cryptomeriae , M. decoratus and M. fujisanus , and their holotypes (all females). However, while Okutani (1958) wrote “Antennae with 25 rami” for the male paratypes of M. itoi , 43 males from Kanagawa have an antenna with 27–30 rami. This may suggest that the Kanagawa specimens are not M. itoi . If so, they belong to an undescribed species. Unfortunately, all the type specimens of M. itoi are most likely to have been lost. Based on our current material, it would be reasonable to consider that the Kanagawa specimens are M. itoi and that the difference in the number of antennal rami is included in intraspecific variation.

This species is separated from other species as stated in the key and the remarks of M. cryptomeriae . In addition to the characters in the key, this species is distinguished from M. cryptomeriae and M. decoratus by having a female antenna with 19–21 antennomeres and a flagellomere 6 in the lateral view with the breadth including the serration 1.8–2.1 × the dorsal length ( Fig. 7A View FIGURE 7 1 View FIGURE 1 ) (antennomeres less than 18 and a flagellomere 6 with the breadth less than 1.8 × the dorsal length in the latter two species, Figs 12G, H View FIGURE 12 , 13E View FIGURE 13 ).