REVISION OF THE GENUS OROSIUS DISTANT (HOMOPTERA : CICADELLOIDEA) BY By M. S. K. GHAURI SYNOPSIS The genera Orosins Distant and Nesophrosyne Kirkaldy are redefined and their status estab-lished. Species of Orosius are redescribed and illustrated. A new species of Orosius is described. MEMBERS of the genus Orosius Distant (19186 : 85) have been recognized as serious virus vectors affecting economic plants in many parts of the world ; causing con-siderable losses to sesamum (Sesamum orientate L.) in India (Vasudeva & Sahambi, 1955 and 1958), and to tomato, tobacco and lucerne in Australia (Helson, 19510 and Heinze, 1951 : 33). In India alone, the loss to sesamum through Phyllody has been estimated by Vasudeva & Sahambi (1958) as more than three and a half million pounds sterling per year. The same authors found several other crops, winter oilseeds (Brassica spp.), sanhemp (Crotalaria juncea L.), gram (Cicer orientum L.), berseem (Trifolium alexandrium) and many others, susceptible to the virus disease carried by the same vector. The importance of Orosius argentatus (Evans, 19386 : 15) was recognized even earlier (vide Oman, 19490 : n) as virus vector of tomato big bud and tobacco yellow dwarf. In spite of their economic importance, the identity of the virus vectors belonging to this group was not clearly understood. Thus they have been known by different names, Nesaloha cantonis Oman (19436 : 33), Deltocephalus sp. (Vasudeva & Sahambi, 1958), Orosius argentatus (Evans, 19386) (Day & McKinnon, 1951) and Nesophrosyne (Orosius) lotophagorum Kirkaldy (Linnavuori, 19600 : 56). Evans (in litt.) has expressed doubt as to whether differences between these should be regarded as of specific significance. Other species, such as Orosius albicinctus Distant (19186 : 85), Thamnotettix cellulosa Lindberg (19270 : 90), Thamnotettix filigranus Haupt (19270 : 30), Thamnotettix canberrensis Evans (19386 : 15) and Orosius maculatus Singh-Pruthi (19300 : 67) are also involved. There was, thus, a need for re-describing various species as well as for establishing their correct generic relationships. Distant (19186 : 85) described Orosius, with Orosius albicinctus Distant as the type-species by monotypy. Later only two other species were described in Orosius. These are Orosius maculatus Pruthi (19300 : 67) and Orosius santali Pruthi (19340 : 25). Orosius maculatus Pruthi has been designated the type-species of Pruthiorosius by the writer (Ghauri, 1964 : 559). Orosius santali Pruthi was not available for the present study. Haupt (19270 : 30, T. filigranus) and Lindberg (19270 : 90, T. cellulosa} described one species each under Thamnotettix and Evans (19386 : 15) added two more species T. argentatus and T. canberrensis. Oman (19436 : 33) described another species Nesaloha cantonis, referable to Orosius. Oman (19490 : ENTOM. 1 8, 7. 1 8
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