Chrysorthenches drosochalca

This species was first described by Edward Meyrick in 1905 using specimens collected at Ōtira Gorge and Wellington and named Orthenches drosochalca.[4] George Hudson discussed and illustrated this species in his 1928 book The butterflies and moths of New Zealand.[5] In 1996 J. S. Dugdale placed this species in the genus Chrysorthenches.[2] The male lectotype, collected by George Hudson in Wellington, is held at the Natural History Museum, London.[6][2]

Illustration of C. drosochalca by Hudson.

Hudson described the larva and pupa of this species as follows:

The larva ... is about 1⁄4 inch in length, cylindrical tapering at each end with the segmental divisions deeply excised, uniform dark green and shining. The pupa is enclosed in a small oval cocoon fastened to a fern frond.[5]

Meyrick described the adults of this species as follows:

♂♀. 11mm. Head and thorax leaden-grey. Palpi dark fuscous, inwardly and towards base white, terminal joint half as long again as second (1+1⁄2). Antennae dark fuscous, ringed with white. Abdomen grey, towards base pale ochreous, apex in ♂ whitish. Fore-wings elongate, costa moderately arched, apex pointed, termen sinuate, rather strongly oblique, rounded beneath ; 7 to termen ; shining coppery-bronze ; four oblique fasciae of white irroration, first slender, second antemedian, broader, third angulated, considerably enlarged towards costa, fourth forming an apical patch extended along termen ; a spot on base of costa, an interrupted streak along submedian fold, and a spot above middle of disc purple ; a dark fuscous-purple transverse mark in disc at 2⁄3, in third fascia : cilia light grey, above apex spotted basally with purplish. Hind-wings ovate-lanceolate, apex acute, termen sinuate ; light grey, darker posteriorly ; cilia whitish-grey.[4]

This species is variable in size and in the intensity of the ground colour of the forewings.[5] It can be distinguished from similar appearing species as its forewings have very scattered white scales as well as a more brassy foreground colour.[2]

C. drosochalca is endemic to New Zealand.[1] It has been observed in both the North and South Islands.[5]

The larvae feed in January.[5] Adults are on the wing from January until March.[5] The species has been collected by beating Prumnopitys ferruginea.[5] When resting the forewings are closed giving the moth the appearance of a cylinder.[5] Both the larvae and the adult moth appear to overwinter.[2]

Larval host P. ferruginea.

The larval host of this species is Prumnopitys ferruginea with the larvae of C. drosochaica mining the leaves of its host.[2]

In 2020 this species along with the other species in the genus Chrysorthenches had their morphological characters studied.[7]