Laccotrephes

Abstract: 35 species of aquatic and semi-aquatic Hemiptera taken in ephemeral pools and pans at 21 collecting sites in 2 regions of Southern Rhodesia are recorded. Ecological conclusions on the habitat “preferences” of some of these species are described and comparisons are made with collections from equivalent habitats in South Africa, East Africa, Abyssinia and Arabia. Differences in alkalinity, pH and acidity have no detectable effect on the occurrence of species, but the physical conditions of the habitat appear to be critical (e.g. size, depth of pool, temperature, etc.). The majority of the aquatic Hemiptera from these temporary pools and pans are widespread Ethiopian species, e.g. Anisops pellucens, A. varia, A. debilis (Some occur also in Arabia), or are Ethiopian-Oriental species, e.g. Anisops sardea, Laccotrephes brachialis, Mesovelia vittigera and the remainder of the fauna consists of a few endemic (regionally abundant) species. Such endemics are for instance Anisops convexonota in Arabia, A. worthingtoni in Kenya, A. hancocki and A. jaczewski in East and Central Africa, A. aglaia in the Transvaal and Cape Province. It is suggested that the widespread Ethiopian species may show more complete adaptation and versatility to life in pans than regionally occurring species, and that the zoogeographic spread of Ethiopian species may be restricted in part by climatic change (e.g. temprature) and in part by the restriction of “pans” themselves to certain climatic regions. It would be extremely difficult to differentiate between such effects. These results are discussed in relation to recent zoogeographic studies in Africa.

Abstract: Predation experiments using Gerris (A) spinolae, Laccotrephes griseus and Gambusia affinis were conducted against IV stage culicine larvae with varying prey densities. Ranking of individual predatory efficiency showed the sequence: large Gambusia > medium Gambusia > small Gambusia > female Laccotrephes > male Laccotrephes > Gerris. Predation under coexistence reveals the significance of predatory efficiency of different predator combinations with reference to prey density and exposure period.