Ametastegia luridiventer Takeuchi, 1952

Ametastegia luridiventer Takeuchi, 1952

( Fig. 1A–F View Fig )

Materials examined. JAPAN: HONSHU— Tokyo Met.: 1 female, Hachioji-shi, Uratakaomachi , Kogesawa , 31. VIII. 2019 , Y. Kato; 1 female, same data as above, except for 7. IX; 1 female, same data as above, except for 2. V. 2021 ; 1 female, same data as above, except for 23. IX; 1 female, Hachioji-shi, Uratakaomachi, Oshimo , oviposited on Fallopia japonica var. japonica in field and captivity, YK20200912A, 12. IX. 2020 , Y. Kato; 1 final instar larva (in ethanol), offspring of YK20200912A, hatched 17. IX, fixed 5. X, Host : Fallopia japonica var. japonica ; 1 final feeding instar larva (in ethanol), same data as above, except for fixed 6. X; 1 male, same data as above, except for hatched 17–18. IX, mat. 5. X., emerged 1–20. XII. 2020 .

Larva. ɹ Early instar ( Fig. 1B View Fig ): Length about 2 mm; head brown to dark brown, with ocularium and stemmatum black; trunk translucent white. Middle instar ( Fig. 1C View Fig ): Length 5–10 mm; head bluish gray dorsally and whitish gray ventrally, with ocularium and stemmatum black; trunk translucent white, abdominal segment each with pair of obscure black spots on supraspiracular zone. Final feeding instar ( Fig. 1D, E View Fig ): Length about 14 mm; color similar to middle instar, but obscure black spots on supraspiracular zone distinct and with large black spot on abdominal tergum 10. Final instar (= mature larva) ( Fig. 1F View Fig ): Length about 14 mm; similar to final feeding instar, but ground color dark greenish gray dorsally, dark creamy white ventrally. Trunk covered with thin layer of white wax in all feeding instars.

Host plant. ɹ Polygonaceae : Fallopia japonica (Houtt.) Ronse Decr. var. japonica (new record).

Observations and rearing records. ɹ On September 12, 2020 , I observed a female ovipositing on a leaf of Fallopia japonica in Oshimo , Uratakaomachi , Hachioji City , Tokyo Metropolis , 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 10 or more eggs on the same plant from September 12 to 13. The eggs were individually inserted in the tissue of the leaf from the upper surface ( Fig. 1A View Fig ). All eggs hatched between September 17 and 18. The larva always stayed on the undersurface of the leaf, with the coiling resting position ( Fig. 1E View Fig ). Three larvae reached the final feeding instar from October 1 to 2 and the others died. One of them was fixed in ethanol on October 6. The remaining larvae executed extra molts and matured from October 5 to 6. They entered the decaying wood, not the soil. A male adult emerged on December 15 to 20, 2020 .

Life history. ɹ Adults were collected in early May and late August to late September in Hachioji City , Tokyo, Japan (see collection data above) . According to my rearing records, one larva that hatched in mid-September matured in early October and became an adult in the same year. Therefore, this species is probably multivoltine in Honshu, Japan .

Remarks. ɹ The larva and host plant are recorded here for the first time. Among the Japanese congeners, the larva of Ametastegia polygoni Takeuchi, 1929 is also known to feed on Fallopia japonica (Hara et al., 2022) . The final feeding instar larva of A. luridiventer is easily distinguished from that of A. polygoni by the each abdominal segment with a pair of distinct black spots on the supraspiracular zone (no black spots on the trunk in A. polygoni , fig. 3C, D in Hara et al., 2022).