Distribution of Oviposition Sites and Characteristics of Egg Development in the 'Blandford Fly' Simulium posticatum (Diptera: Simuliidae)

Abstract

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An historical perspective of the ?Blandford Fly? (Simulium posticatum Meigen) problem and attempted control of the pest species using Bacillus thuringiensis var. israelensis

“…Williams personal communication). Experimental studies on resistance to desiccation suggest that there is only a slight difference in the tolerance of low humidities between the eggs of S. posticatum and those of S. ornatum (Welton et al 1987). Exposed to relative humidities of less than 87%, no eggs of either species survived.…”

“…Unlike many other species of Simulium which oviposit in close proximity to the water surface and have a brief egg development time (Fredeen et al 1951;Zahar 1951;Ruhm 1971;Welton and Bass 1980;Wotton 1987), the eggs of S. posticatum are laid in the river bank, above the water surface, in June and do not hatch until the following February-March (Ladle et al 1985;Welton et al 1987). The eggs themselves are similar in size and shape to those of many other simuliids and the membranes do not appear to be very different from those of species having brief development periods such as S. ornatum or Simulium lineatum (T.R.…”

“…Sites with a vertical bank profile, loamy, moist, shallowly cracked soil in the shade are favoured for oviposition. The aspect of the river bank is also related to the choice of oviposition site (Welton et al 1987).…”

Review of blackfly (Diptera : Simuliidae) control in South Africa

“…In addition to feeding on sugar, which is used as a fuel for flight (Hocking 1953;Davies, Peterson & Wood 1962;Hunter 1977;Sutcliffe 1986), anautogenous adult female blackflies also require a blood meal (Welton, Bass, Ladle & Merritt 1987;Palmer 1997;Gibson & Torr 1999) for ovarian development (Davies & Peterson 1956;Peterson 1959;Crosskey 1990). Because of their blood-feeding activity they are considered ideal disease vectors (Crosskey 1990) and are probably best known for transmitting the filarial nematode Onchocerca volvulus to humans (Nelson 1991;Davies 1994;Hougard, Yaméogo, Sékétéli, Boatin & Dadzie 1997;Gibson & Torr 1999).…”

Life history patterns of river invertebrates

“…These are interactive with variations in food supply and other ecological variables. For example slow flow has been found to be associated with the attainment of large body size in chironomids (Welton et al, 1987). The interpretation of these phenomena is rendered more complex by the relationship between population density and size in some chironomids which may become cannibalistic at high population densities (McLachlan, 1989).…”