Study of the food-searching activity by smell in diving beetles of Cybister Curtis, 1827 and Hydaticus Leach, 1817 (Coleoptera: Dytiscidae) including the use of a microwave Doppler radar

To investigate how four species of Cybister Curtis, 1827 and one species of Hydaticus Leach, 1817 (Coleoptera: Dytiscidae) detect food, insects were provided with dried sardines using traps made by a three-dimensional printer. More than 83% of the beetles found the sardine hidden in the trap. When the two traps were set in an aquarium—one contained a dried sardine before extraction with boiled water, and another contained a dried sardine after extraction—more than 90% of beetles were caught in the trap with the sardine before extraction. In contrast, less than 3% of beetles entered the trap with the sardine after extraction. No feeding preference was found between the sardines before and after extraction. A microwave Doppler radar was used to quantitatively detect the behaviour using broth extracted from the sardines, and the broth enhanced the food-searching activity. These results suggest that these beetles use smell to find food, and their searching activities are induced by smell.

为探究4种龙虱属（Cybister Curtis, 1827）及1种水龙虱属（Hydaticus Leach, 1817）鞘翅目（Coleoptera）龙虱科（Dytiscidae）昆虫的食物检测机制，本研究采用三维打印机（three-dimensional printer）制作的诱捕装置，以干沙丁鱼作为食物诱饵开展实验。超83%的龙虱成功发现藏匿于诱捕装置内的沙丁鱼。当将两组诱捕装置放置于水族箱中时——一组放置经沸水萃取处理前的干沙丁鱼，另一组放置经沸水萃取处理后的干沙丁鱼——超90%的龙虱会被放置萃取前沙丁鱼的诱捕装置捕获；与之相反，仅不足3%的龙虱会进入放置萃取后沙丁鱼的诱捕装置。研究未发现龙虱对萃取前后的沙丁鱼存在取食偏好性差异。本研究采用微波多普勒雷达（microwave Doppler radar），以沙丁鱼浸出液为样本对龙虱行为进行定量检测，结果显示该浸出液可显著提升龙虱的觅食搜索活性。上述结果表明，此类龙虱依靠嗅觉搜寻食物，其觅食搜索行为由嗅觉信号诱导触发。