The range of attraction for light traps catching Culicoides biting midges (Diptera: Ceratopogonidae)

Carsten Kirkeby,Kaare Græsbøll,Anders Stockmarr,René Bødker,Lasse E Christiansen

doi:10.1186/1756-3305-6-67

Abstract

BackgroundCulicoides are vectors of e.g. bluetongue virus and Schmallenberg virus in northern Europe. Light trapping is an important tool for detecting the presence and quantifying the abundance of vectors in the field. Until now, few studies have investigated the range of attraction of light traps.MethodsHere we test a previously described mathematical model (Model I) and two novel models for the attraction of vectors to light traps (Model II and III). In Model I, Culicoides fly to the nearest trap from within a fixed range of attraction. In Model II Culicoides fly towards areas with greater light intensity, and in Model III Culicoides evaluate light sources in the field of view and fly towards the strongest. Model II and III incorporated the directionally dependent light field created around light traps with fluorescent light tubes. All three models were fitted to light trap collections obtained from two novel experimental setups in the field where traps were placed in different configurations.ResultsResults showed that overlapping ranges of attraction of neighboring traps extended the shared range of attraction. Model I did not fit data from any of the experimental setups. Model II could only fit data from one of the setups, while Model III fitted data from both experimental setups.ConclusionsThe model with the best fit, Model III, indicates that Culicoides continuously evaluate the light source direction and intensity. The maximum range of attraction of a single 4W CDC light trap was estimated to be approximately 15.25 meters. The attraction towards light traps is different from the attraction to host animals and thus light trap catches may not represent the vector species and numbers attracted to hosts.

Highlights

Culicoides are vectors of e.g. bluetongue virus and Schmallenberg virus in northern Europe
The attraction towards light traps is different from the attraction to host animals and light trap catches may not represent the vector species and numbers attracted to hosts
Few studies have attempted to estimate the range of attraction for light traps: Odetoyinbo [8] carried out a study where a trap was hung at different distances from an open window which mosquitoes passed through at night

Summary

Introduction

Culicoides are vectors of e.g. bluetongue virus and Schmallenberg virus in northern Europe. Biting midges (Diptera: Ceratopogonidae: Culicoides) are vectors of e.g. Bluetongue virus [1] and the newly discovered Schmallenberg virus in northern europe [2] Due to their crepuscular activity pattern, the standard trapping method is by (UV) light traps [3]. Many different terms have been used for this measure, and we prefer to use the ‘range of attraction’, describing the (maximum) distance at which insects are attracted to the trap. The ‘range of attraction’ was the distance at which the two traps began to catch less than the independent trap Both of these last studies hypothesized that Culicoides are attracted to the nearest trap, and that the light from the trap is isotropic (uniform in all directions). In the present study we incorporated the directionally dependent (anisotropic) light created by the light tubes in the light traps into two novel models for the attraction of Culicoides to light traps

Methods

Discussion

Conclusion