Parasitism of Grasshopper and Locust Eggs (Orthoptera: Acrididae) by Scelio Species (Hymenoptera: Scelionidae) in Southern Australia

Abstract

Surveys of Scelio spp., parasites of acridid eggs, were conducted in southern Australia during 1990-94. Parasitism of economically important grasshopper and locust species was frequently substantial confirming an important, albeit often localised, role by Scelio spp. in regulating host populations. Parasitism of Phaulacridium vittatum eggpods in tableland districts averaged 33.5% +/- s.d. 9.5 (range 27.4-47.1) and Chortoicetes terminifera throughout southern Australia averaged 19.8% +/- s.d. 24.6 (range 0-78.9). Scelio spp. were stenophagous and although some species parasitised several hosts, typically a principal host was readily identifiable. Scelio parvicornis was an exception in having two equally important hosts (P. vittatum and C. terminifera) and several subordinate alternative hosts (Oedaleus australis, Brachyexarna lobipennis and A. vulgaris). New hosts were recorded for S. fulgidus (Gastrimargus musicus), S. chortoicetes (Austroicetes vulgaris), S. parvicornis (Brachyexarna lobipennis, P. vittatum and A. vulgaris), S. flavicornis (C. terminifera), S. sp. nr flavicornis (Praxibulus insolens), S. ignobilis (Aiolopus thalassinus tamulus), S. bipartitus (C. terminifera) and S. orientalis (P. insolens). Significant new geographic distributions include S. parvicornis, S. fulgidus, S. sp. nr improcerus and S. flavicornis from Western Australia and S. orientalis and S. ignobilis from New South Wales. Undescribed species were reared from 29 pods of C. terminifera, P. vittatum, Macrotona australis and P. insolens.