Spilosoma strigatula Walker

Spilosoma strigatula Walker, 1855, List Specimens lepid. Insects Colln Br. Mus., 3: 613.

Diagnosis

The ground colour is dull brownish red as in griseabrunnea, but strigatula is smaller with the forewings more heavily suffused with brown and flecked with black. The submarginal band of the hindwing is more complete. The male genitalia of the two species differ as illustrated.

Taxonomic notes

This and the next species (griseabrunnea and hypogopa) belong to a small group of dark reddish Sundanian taxa. A common feature of the male genitalia is the presence of a single spine centred on a rather umbonate sclerotisation at the apex of the aedeagus. Bornean material of strigatula has the lateral processes of the valves more at the same level than in typical Javan material.

The identity of S. griseabrunnea Holloway has been explored further in relation to a number of very similar species in southeast Asia (the strigatula Walker group) by Dubatolov & Kishida (2010). They described a new subgenus, Praephragmatobia Dubatolov & Kishida for the group and recognised three subgroups within it. The typical group includes strigatula, gurkoi Dubatolov (Mentawi Is.), sumatrana Swinhoe (Sumatra) and continentalis Rothschild (Peninsular Malaysia). The second group contains griseabrunnea, cervina Walker (Sumatra and islands to the west, Peninsular Malaysia) and rubescens Walker (Burma and Yunnan to Sumatra). The third group consists of three new species distributed allopatrically over the Philippines archipelago, including Palawan. It has not been possible to assess whether these species are the same as those described by Cerný (2011).

Geographical range

Sundaland, Thailand.

Habitat preference

The species is rarer than the next, recorded only from Bidi in Sarawak and the Sandakan district of Sabah, both lowland localities.

Biology

The larva and cocoon were illustrated by Horsfield & Moore (1858-9). The larva has a dark brown skin with pale orange-brown tufts of short setae amid longer setae on the verrucae. It was suggested to be polyphagous, Dioscorea (Dioscoreaceae) being the only named host-plant. Pholboon (1965) recorded the following host-plants in Thailand: