Department of Biological Physics, ELTE Eötvös Loránd University, Budapest, Hungary.
Department of Zoology, Hungarian Natural History Museum, Budapest, Hungary.
PLoS One. 2020 May 13;15(5):e0233038. doi: 10.1371/journal.pone.0233038. eCollection 2020.
Blood-sucking horseflies (tabanids) prefer warmer (sunlit, darker) host animals and generally attack them in sunshine, the reason for which was unknown until now. Recently, it was hypothesized that blood-seeking female tabanids prefer elevated temperatures, because their wing muscles are quicker and their nervous system functions better at a warmer body temperature brought about by warmer microclimate, and thus they can more successfully avoid the host's parasite-repelling reactions by prompt takeoffs. To test this hypothesis, we studied in field experiments the success rate of escape reactions of tabanids that landed on black targets as a function of the target temperature, and measured the surface temperature of differently coloured horses with thermography. We found that the escape success of tabanids decreased with decreasing target temperature, that is escape success is driven by temperature. Our results explain the behaviour of biting horseflies that they prefer warmer hosts against colder ones. Since in sunshine the darker the host the warmer its body surface, our results also explain why horseflies prefer sunlit dark (brown, black) hosts against bright (beige, white) ones, and why these parasites attack their hosts usually in sunshine, rather than under shaded conditions.
吸血虻（虻科）更喜欢温暖（阳光充足、较暗）的宿主动物，通常在阳光下攻击它们，这一原因至今仍不清楚。最近，有人假设吸血的雌性虻更喜欢较高的温度，因为在温暖的微气候下，它们的翅膀肌肉更快，神经系统功能更好，因此可以通过迅速起飞来更成功地避免宿主的驱虫反应。为了验证这一假设，我们在野外实验中研究了虻降落在黑色目标上时逃避反应的成功率与目标温度的关系，并通过热成像测量了不同颜色马匹的表面温度。我们发现，虻的逃避成功率随着目标温度的降低而降低，也就是说逃避成功率受温度驱动。我们的研究结果解释了吸血虻的行为，它们更喜欢温暖的宿主而不是较冷的宿主。由于在阳光下，宿主的颜色越深，其体表温度越高，因此我们的研究结果也解释了为什么虻更喜欢阳光充足的深色（棕色、黑色）宿主而不是浅色（米色、白色）宿主，以及为什么这些寄生虫通常在阳光下而不是在阴凉处攻击它们的宿主。
