Eutomostethus togashii Seiyama, 1981

Eutomostethus togashii Seiyama, 1981

( Fig. 1G–K View Fig )

Material examined. ɹ JAPAN: HONSHU— Saitama Pref.: 1 female, Koshigaya-shi, Sagamicho, Motoarakawa River (oviposited on Carex sp. in field and captivity), 21. IV. 2023, Y. Kato .

Larva. ɹ Early instar ( Fig. 1H View Fig ): Length about 2 mm; head dark brown, with ocularium and stemmatum black; trunk translucent white. Middle instar ( Fig. 1I View Fig ): Length 3–8 mm; head pale brown, with ocularium, stemmatum and small spot on posterior end of vertex black; trunk translucent white to yellowish white. Final feeding instar ( Fig. 1J View Fig ): Length about 10 mm; color similar to middle instar, but dorsal half of trunk pale gray, with supraspiracular region dark gray. Final instar (= mature larva) ( Fig. 1K View Fig ): Head white to light brown; trunk translucent white to yellowish white, cuticle smooth and shiny.

Host plant. ɹ Cyperaceae : Carex sp. (new record).

Observations and rearing records. ɹ On April 21, 2021, I observed a female ovipositing on a leaf of Carex sp. in the riverbed of the Motoarakawa River , Koshigaya City , Saitama Prefecture, Honshu , Japan. After observing oviposition, I collected this female and kept it alive in a container with the same live plant species, and it laid 11 eggs on the same plant between April 21 and 23. The eggs were individually inserted in the tissue of the leaf from the lower surface ( Fig. 1G View Fig ). All eggs hatched between May 2 and 4. The hatched larvae solitarily fed on the leaf edge. One larva executed an extra molt and matured on May 27. It entered the soil on the same day. The other 10 larvae died before maturity. No adult emerged .

Life history. ɹ Naito (2020) noted that E. togashii was a univoltine species and the adults occur in spring to summer, but he did not present any evidence. On the other hand, in the quantitative survey conducted at the Imperial Palace, the lowland of Tokyo, Honshu, Japan ( Shinohara, 2000, 2014), adults were collected from mid- April to early June and from late August to early September, possibly suggesting a multivoltine life cycle.

Remarks. ɹ The larva and host plant are recorded here for the first time. The Japanese congener, Eutomostethus pumicosus Seiyama, 1981 is also known to feed on Carex sp. ( Seiyama, 1981), but the larva of this species is still undescribed. Therefore, the larvae of the two species cannot be distinguished at this time.