Nexosa hexaphala Meyrick 1912

Nexosa hexaphala (Meyrick, 1912)

(Figs. 1, 2–3, 7)

Mictopsichia hexaphala Meyrick, 1912, Exot. Microlepidoptera, 1: 36. Type locality: Maskeliya, Sri Lanka.

Diagnosis. Wing expanse: 14 mm (n = 1). This species is notable for the extensive white on the hindwings in both males and females, whereas the new species from Vietnam has darker hindwings in the female, with less white evident. The white hindwing of the female N. hexaphala can be noted in the figure of the holotype shown by Clarke (1969).

Diakonoff (1977) erroneously stated that Clarke (1969) had illustrated the female genitalia of N. hexaphala, but Diakonoff mistook a figure of the genitalia of a Neotropical species of Mictopsichia illustrated above that for N. hexaphala: the holotype female lacks an abdomen as Clarke noted. Because the species has not had a modern description, and none for the genitalia, a redescription is given in more detail herein based on the new Vietnam subspecies which can be compared to the Sri Lanka population of the nominate subspecies, which otherwise is known from only a single specimen.

Specimens recorded. Holotype female: Maskeliya, [Ratnapura Dist.], Ceylon [Sri Lanka], May 1906, de Mowbray (BMNH).

Distribution. The nominate subspecies, N. hexaphala hexaphala, is known only from Sri Lanka.

Discussion. The description below for the Vietnam subspecies is essentially the same as for the Sri Lanka nominate subspecies, as far as can be determined at this time, except for the following points: forewing with fewer black-brown spots near base at 1/3 and the hindwing with much larger black patch on the termen and tornus and with two brown patches near the wing base (only one in the Vietnam specimens). The female holotype from Sri Lanka remains the single known female of this species and lacks an abdomen, thus the genitalia are not known and cannot be compared with the Vietnam congeners. Although the female would be expected to differ somewhat in maculation from the male, some aspects of the hindwing, as well as the great distance from Sri Lanka to northern Vietnam and no intervening records in India, Burma, Thailand, or Laos, suggest that the Vietnam population should be treated as a separate subspecies from those in Sri Lanka.