Biological studies on two sibling species of Lixophaga (Diptera: Tachinidae), parasites of the New Guinea sugarcane weevil, Rhabdoscelus obscurus (Boisduval).
The Tachinid Lixophaga sphenophori (Villen.) was successfully introduced into Hawaii for control of Rhabdoscelus obscurus (Boisd.) on sugar-cane in 1910. Cross-breeding experiments with Lixophaga from New Guinea and Hawaii indicated that populations of L. sphenophori already present in Hawaii were reproductively isolated from those recently imported from highland localities at Wau and Garaina in eastern New Guinea. Populations from the last two areas were interfertile and appeared to represent an undescribed sibling species of Lixophaga. The ancestors of the Hawaiian population were obtained from a lowland locality near Port Moresby, and the undescribed form possibly represents a highland homologue of lowland populations in New Guinea. Minor differences were found in the colour of the dorsal pollinosity and the structure of the male genitalia in adults of the two species. Mature larvae were readily separated by morphological differences in the posterior spiracles, mouth hooks and cephalopharangeal skeleton.