A horizontally polarizing liquid trap enhances the tabanid-capturing efficiency of the classic canopy trap

Abstract

Host-seeking female tabanid flies, that need mammalian blood for the development of their eggs, can be captured by the classic canopy trap with an elevated shiny black sphere as a luring visual target. The design of more efficient tabanid traps is important for stockbreeders to control tabanids, since these blood-sucking insects can cause severe problems for livestock, especially for horse-and cattle-keepers: reduced meat/milk production in cattle farms, horses cannot be ridden, decreased quality of hides due to biting scars. We show here that male and female tabanids can be caught by a novel, weather-proof liquidfilled black tray laid on the ground, because the strongly and horizontally polarized light reflected from the black liquid surface attracts water-seeking polarotactic tabanids. We performed field experiments to reveal the ideal elevation of the liquid trap and to compare the tabanid-capturing efficiency of three different traps: (1) the classic canopy trap, (2) the new polarization liquid trap, and (3) the combination of the two traps. In field tests, we showed that the combined trap captures 2.4-8.2 times more tabanids than the canopy trap alone. The reason for the larger efficiency of the combined trap is that it captures simultaneously the host-seeking female and the water-seeking male and female tabanids. We suggest supplementing the traditional canopy trap with the new liquid trap in order to enhance the tabanid-capturing efficiency.

Morphological re-description and molecular identification of Tabanidae (Diptera) in East Africa

“…The conservation areas of Shimba Hills in Kenya were found to have a more varied range of tabanids despite the fact that the tabanid flies were not the main target of the collection but rather the tsetse fly. Traps routinely used for tsetse flies (NG2G and biconical) ( Egri et al 2013 ; Allsopp 1984 ) were used in Kenya and Tanzania and this may have led to non-exhaustive sampling. The varied range may be attributed to by the higher number of tabanids that were collected in the Shimba Hills compared to numbers collected in other study areas.…”

Why do horseflies need polarization vision for host detection? Polarization helps tabanid flies to select sunlit dark host animals from the dark patches of the visual environment

“…The observed double polarotaxis in horseflies has been explored as the basis of polarization-based horsefly traps [ 32 ]: water-seeking horsefly males and females are attracted to these traps by horizontally polarized bait-reflected light, where the bait is a shiny (smooth) black horizontal surface (sticky board, oil surface or photovoltaic solar panel) mimicking a horizontally polarizing water surface [ 28 , 33 , 34 ]. Furthermore, host-seeking females are lured by vertical plane or spherical shiny (smooth) black targets suspended above the ground, imitating dark and strongly polarizing host animals [ 23 , 28 , 34 ]. Like polarotactic aquatic insects in general [ 35 ], horseflies are only weakly attracted to matt (rough) black or matt dark-coloured surfaces [ 2 , 22 , 23 , 36 , 37 ].…”

Insect Responses to Linearly Polarized Reflections: Orphan Behaviors Without Neural Circuits

“…Hence, polarized reflections are used in this case to increase the perceived visual contrast. Some true flies (Diptera) not only show strong attraction to polarized surfaces, but also linearly polarized objects, which was demonstrated for blood-sucking horse flies (Tabanidae; Horváth et al, 2008 ; Egri et al, 2013 ). Some of these behaviors are most likely involved in prey detection since polarimetric imaging of horses and cattle reveals strong linearly polarized reflections off their fur (Horváth et al, 2010 ).…”