. The Entomologist's record and journal of variation. so play a part insuppressing allopatric hybridization in this zone of contactbetween clytus and oxylus. Thus clytus appears to favour thesweeter grasses while oxylus appears to follow the distributionof the sourveld. The boundaries separating these grass typescoincide with the zone of contact between clytus and oxylusfrom Queenstown down through Stutterheim. Genetic incompatibility possibly plays a minor role inpreventing appreciable introgression between clytus and for this view is provided by the lack of constantcharacter d
. The Entomologist's record and journal of variation. so play a part insuppressing allopatric hybridization in this zone of contactbetween clytus and oxylus. Thus clytus appears to favour thesweeter grasses while oxylus appears to follow the distributionof the sourveld. The boundaries separating these grass typescoincide with the zone of contact between clytus and oxylusfrom Queenstown down through Stutterheim. Genetic incompatibility possibly plays a minor role inpreventing appreciable introgression between clytus and for this view is provided by the lack of constantcharacter differences between the two taxa, except in a veryminor feature of the male genitalia, and that clinal patternsare the same for both species. Everything considered, theclytus/oxylus zone of contact is a narrow one, and eventhough secondary contact between the two was establishedbefore full reproductive isolation was attained, they havediverged sufficiently for each to maintain themselves asseparate species over virtually their entire range. PLATE III. Fig. II. Male genitalia of two Dira species. (A) D. clytus: Stutterheim. (B) D. oxylus: Stutterheim. 1. Uncus. 2. Sciaphium. 3. Valves. 4. Aedeagus. 5. Juxta. PLATE IV
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