Explaining the Host-Finding Behavior of Blood-Sucking Insects: Computerized Simulation of the Effects of Habitat Geometry on Tsetse Fly Movement

Abstract

BackgroundMale and female tsetse flies feed exclusively on vertebrate blood. While doing so they can transmit the diseases of sleeping sickness in humans and nagana in domestic stock. Knowledge of the host-orientated behavior of tsetse is important in designing bait methods of sampling and controlling the flies, and in understanding the epidemiology of the diseases. For this we must explain several puzzling distinctions in the behavior of the different sexes and species of tsetse. For example, why is it that the species occupying savannahs, unlike those of riverine habitats, appear strongly responsive to odor, rely mainly on large hosts, are repelled by humans, and are often shy of alighting on baits?Methodology/Principal FindingsA deterministic model that simulated fly mobility and host-finding success suggested that the behavioral distinctions between riverine, savannah and forest tsetse are due largely to habitat size and shape, and the extent to which dense bushes limit occupiable space within the habitats. These factors seemed effective primarily because they affect the daily displacement of tsetse, reducing it by up to ∼70%. Sex differences in behavior are explicable by females being larger and more mobile than males.Conclusion/SignificanceHabitat geometry and fly size provide a framework that can unify much of the behavior of all sexes and species of tsetse everywhere. The general expectation is that relatively immobile insects in restricted habitats tend to be less responsive to host odors and more catholic in their diet. This has profound implications for the optimization of bait technology for tsetse, mosquitoes, black flies and tabanids, and for the epidemiology of the diseases they transmit.

Effects of vector control on the population structure of tsetse ( Glossina fuscipes fuscipes ) in western Kenya

“…CS derived from wing measurement can be used as an estimate for adult insect body size (Dujardin, 2008;Lorenz et al, 2017). In tsetse, fly size is among the factors associated with displacement rates, with larger flies having a higher displacement potential than smaller flies (Vale et al, 2014). Displacement rates affect performance of targets (Vale et al, 2014).…”

“…However, controlling the vector is considered the most desirable way of managing African trypanosomiasis (Bouyer et al, 2010;Leak, 1998;Vreysen et al, 2013) but, in the absence of area-wide control interventions covering biologically relevant areas and targeting isolated tsetse populations, re-invasion is commonly reported (Bouyer et al, 2007b;Kaba et al, 2012;Schofield and Kabayo, 2008). Some vector control techniques such as the use of targets exploit the host seeking behaviour which to a larger extent depends on the displacement rates of the tsetse fly (Vale et al, 2014). Among the factors that influence displacement rates is fly size, with the displacement potential increasing as fly size increases (Vale et al, 2014).…”

“…Some vector control techniques such as the use of targets exploit the host seeking behaviour which to a larger extent depends on the displacement rates of the tsetse fly (Vale et al, 2014). Among the factors that influence displacement rates is fly size, with the displacement potential increasing as fly size increases (Vale et al, 2014).…”

“…Fly size is one of the indicators of tsetse population structures and can be obtained from wing measurement (Kaba et al, 2012;Solano et al, 1999). Inter-species variation in tsetse fly size has been associated with differences in displacement rates, responses to attractive and repellent odours, availability to tiny or large targets, persistence and landing responses (Torr et al, 2011;Vale, 1974;Vale et al, 2014Vale et al, , 1984. Interestingly, the fly size of tsetse populations that recover in previously controlled/suppressed areas are rarely reported.…”

Developing photoreceptor-based models of visual attraction in riverine tsetse, for use in the engineering of more-attractive polyester fabrics for control devices

“…These behavioural differences are probably not the result of differences in tsetse physiology. Instead, narrow and densely vegetated riverine habitats mean that odour plumes are of limited utility in host seeking, and the reduced probability of encountering hosts in such habitats necessitates less selectivity when one is encountered [7,17]. Identification of these crucial behavioural differences has allowed the development of ‘tiny targets’ for riverine tsetse, which comprise a 0.25 m x 0.25 m blue polyester panel adjacent to a 0.25 m x 0.25 m black polyethylene mosquito net panel, with both panels impregnated with deltamethrin insecticide [5,10,12,14].…”