Local variation in the population dynamics of <i>Glossina palpalis palpalis</i> (Robineau-Desvoidy) (Diptera: Glossinidae). I. Natural population regulation

Ovarian ages were obtained for tsetse flies Glossina morsitans morsitans Westwood and G. pallidipes Austen caught in Zimbabwe using a stationary bait ox, an odour-baited trap in the presence or absence of humans, a mobile ox fly-round and a vehicle-mounted electric net. The biggest daily catches were obtained from the electric net and the unacccompanied trap, but while for G. m. morsitans the ratio of the catches from these two methods was 7:1, for G. pallidipes it was 0.7:1. Evening catches were 1.3-5.5 and 2.9-18.8 times higher than morning catches for the two species, respectively; the differences were greater for stationary than for mobile baits. The sample age structures differed significantly (P < 0.05: x 2 ) between methods in six of the ten possible contrasts between pairs of methods in G. m. morsitans and for all ten in G. pallidipes. The differences in age distribution and mean catch levels are attributed to increases in flight activity with age; at each age G. pallidipes is more active than G. m. morsitans. Man's presence in the trapping system reduced catches significantly (P < 0.05: t test) but this effect was small in the youngest and oldest flies. Odour-baited traps are biased in favour of G. pallidipes and, for both species, in favour of older flies; mortalities calculated from age distributions of trap samples therefore underestimate the true value.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ovarian ages of tsetse flies (Diptera: Glossinidae) caught from mobile and stationary baits in the presence and absence of humans

Hargrove

1991

“…Finally, the natural mortality is unlikely to depart markedly from 2% per day (.i.e. (p = 0.98) for a non-decreasing population of any species of tsetse fly (Rogers et al, 1984;Hargrove, 1988).…”

Section: T (1)mentioning

confidence: 95%

Target barriers for tsetse flies (Glossina spp.) (Diptera: Glossinidae): quick estimates of optimal target densities and barrier widths

Hargrove

1993

The probability that tsetse flies (Glossina spp.) cross a barrier of odourbaited targets is calculated for barriers of different widths and target density, and for tsetse flies with varying natural rates of survival, daily step lengths (d) and probabilities of being killed by an odour-baited target. If the barrier is only as wide as d, and for a species which has a 2% natural daily mortality and a further 2% mortality due to each target per unit area, tsetse flies have probability (P) of ca. 0.1 of penetrating the barrier even if the target density is 64 per unit area. To ensure that P < 0.001 the barrier must be about 4rf wide for target densities 32 per unit area; doubling the width to 8d means that target densities could be cut by about 75%, and total numbers of targets in the barrier by 50%. These biological considerations and the economic costs of different target barriers suggest that, for all tsetse fly species, a safe and relatively inexpensive barrier is achieved with barrier width 8d when the optimum target density is roughly the same as for normal operational areas. This has the important practical consequence that there is no need to treat barriers as a special case. Practical results from research and control operations in Zimbabwe are in accord with the theoretical findings, but further work is required to ascertain whether the safety margin, and hence costs, can be reduced.

“…(e.g. Dransfield et al, 1982;Rogers et al, 1984). With the identification of specific chemical attractants for tsetse (Vale, 1980;Hall et al, 1984), it is likely that baited traps will increasingly be used.…”

Section: Introductionmentioning

confidence: 99%

“…However, more information is needed on the dose-response relationships for such attractants, as well as on their effects on the composition of samples. The age distribution is of particular interest since this may be of use in estimating monthly changes in survival rate (Rogers et al, 1984). One of the objectives of the work reported here was therefore to investigate these aspects when using various ketones and l-octen-3-ol for sampling G. pallidipes Austen at Nguruman, south-western Kenya.…”

Section: Introductionmentioning

confidence: 99%

The use of odour attractants for sampling Glossina pallidipes Austen(Diptera: Glossinidae) at Nguruman, Kenya

Dransfield

Brightwell

Chaudhury

et al. 1986

Various ketones and l-octen-3-ol were used as odour attractants with biconical traps at Nguruman, south-western Kenya, to assess their effects on the catch size and composition of Glossina pallidipes Austen. Acetone, methyl ethyl ketone and l-octen-3-ol were found to be effective in increasing catch size by up to 2-4 x, but the two ketones differed in their dose-response curves. Acetone was more effective for males than females, as was l-octen-3-ol. The age composition of samples from baited and unbaited traps differed only slightly. The level of variability between traps was reduced by the use of odour. Acetone with cow urine produced increases in catch of 9-25x, and significant differences were found between samples in sex ratio and age composition. The index of increase for cow urine plus acetone, when used with a biconical trap, was correlated with temperature changes during the day. This could only be partially accounted for by variability in dose rates. Cow urine with acetone is considered to be a potentially useful combination of baits for community participation tsetse control schemes.