Mortality of eggs and larvae of the bush fly, Musca vetustissima Walker (Diptera: Muscidae), caused by scarabaeine dung beetles (Coleoptera: Scarabaeidae) in favourable cattle dung

Abstract

The mortality of eggs and larvae of Musca vetustissima Walker, caused by two scarabaeine dung beetles was measured in the laboratory in favourable cattle dung at 23°C. Eggs and larvae less than one day old were the main stages killed in the dung. Mortality from beetles that entered dung immediately after fly oviposition was higher than that from beetles that entered the dung one or three days later. The results also indicated that there are differences between species of dung beetles in the mode of action against the fly. The smaller beetle species, Onthophagus binodis (Thunberg), at densities of 120 beetles/pad caused increased mortalities of 12% of fly eggs and 11% of young larvae but did not affect older larvae, while the larger species, O. ferox Harold, at densities of 48 beetles/pad caused no extra mortality of eggs but did cause an increased mortality of 47% of young fly larvae and 61% of older larvae.

Effects of deforestation on diversity, biomass and function of dung beetles on the eastern slopes of the Peruvian Andes

“…Tropical dung beetles offer a variety of clear ecosystem functions: they prevent soilsurface fouling by burying dung (Myrcha and Andrzejewska, 1984;Cambefort, 1986;Davis, 1996); they aerate soils, improve water penetration and prevent nutrient loss through tunnelling and burial activities (Edwards and Aschenborn, 1987;Herrich and Lal, 1996); they bury seeds and improve seed germination rates (Shepherd and Chapman, 1998;Andresen, 2002Andresen, , 2003 and they reduce populations of flies and other nuisance organisms (Fincher, 1975;Ridsdill-Smith et al, 1987). During the last 50 years, huge tracts of native Neotropical forests have been cleared for timber extraction or for agriculture (Riitters et al, 2000), which negatively affects local dung beetle assemblages (Howden and Nealis, 1975;Klein, 1989;Estrada et al, 1998).…”

“…Dung burial is the initial step to most of the beneficial functions of tropical dung beetles and has been related to the body mass of species in laboratory studies (Doube et al, 1988;Doube, 1990;Horgan, 2001). The burial of dung by beetles and, therefore, the removal of resources for competitors is also a mechanism by which dung breeding fly numbers may be reduced (Ridsdill-Smith et al, 1987). Few comparative field studies from the Neotropics have recorded decomposition, and those that have (i.e., Klein, 1989;Andresen, 2003) do not directly relate decomposition to either dung beetle biomass or species richness.…”

Stages of bush fly, Musca vetustissima (Diptera: Muscidae), killed by scarabaeine dung beetles (Coleoptera: Scarabaeidae) in unfavourable cattle dung

“…This result in unfavourable dung was unexpected, since real mortality was greater for young larvae than for old larvae. In contrast, in favourable dung, the relative mortality of eggs (k, = 0.150), and of young larvae (k 2 = 0.171) in the laboratory at 23°C caused by 120 Onthophagus binodis was greater than mortality of older larvae (k 3 = 0.003) (data from Ridsdill-Smith et al, 1987).…”

“…At this time, live first instar M. vetustissima larvae, and the eggs that had failed to hatch, were extracted from dung by dispersal in water, and then flotation in a soda solution of high specific gravity (Sutherst et al, 1987), and counted. Recovery of eggs by this method is 92%, and of first instar larvae 83% (Ridsdill-Smith et al, 1987), but counts were not corrected for recovery rates. When fly larvae had pupariated, which was confirmed by gently breaking the pad in half and looking for larvae after 7-12 days, the sand and remaining dung were sieved for puparia which were counted.…”

“…vetustissima eggs are susceptible to drowning in dung fluid (Walker & Doube, 1984). When beetles arrive at dung at the time flies oviposit, fewer larvae hatch or survive than when beetles arrive one day later, and presumably the beetles kill M. vetustissima eggs (Hughes etal., 1978;Ridsdill-Smith et a\., 1987). When Onthophagus gazella Fabricius and Onthophagus binodis reduce fly numbers, emerging survivors are sometimes stunted, and presumably the beetles kill older M. vetustissima larvae (Bornemissza, 1970;Ridsdill-Smith et a\., 1986).…”