Genusa simplex Warren

Genusa simplex Warren, 1897, Novit. zool. 4: 88.

Diagnosis

This is the most strongly marked species in Borneo, indeed in the genus, with the mottled grey banding extensive as illustrated. A few specimens (including the holotype) are much more weakly marked.

Taxonomic Notes

The furca has the spining restricted to the apex of each arm; in most other species it extends down the shaft also. In material from Peninsular Malaysia and Sumatra the furca is shorter, each arm two thirds the length of that in Bornean specimens.

S.‐H. Yen (pers. comm.) has studied the life history of the Genusa species in Taiwan. It was unusual in that pupation is on the surface of a leaf and involves an abdominal girdle, the first record of this feature in Geometridae outside the Cosymbiini of the Sterrhinae (see Note 175). The cremaster is also attached to a silken pad. The pupa also has unusual slender black horns on each side of the prothoracic segment and a conspicuous pair of black spots with irregular paler surrounds on the mesothorax. The host plant recorded was Gonocaryum (Cardiopteridaceae (S.‐H. Yen, pers. comm.); previously in Icacinaceae (Mabberley, 1987)). This host plant has also facilitated searches for the genus elsewhere, e.g. Hainan (S.‐H. Yen, pers. comm.).

Geographical Range

Sulu Is. (S. Philippines), Borneo; Peninsular Malaysia, Sumatra.

Habitat Preference

The only recently taken specimen was from 300m in dipterocarp forest, Ulu Temburong, Brunei.

Genitalia: