DISEASE REMOVAL BY ALTERED FLIGHT BEHAVIOR OF FORAGER HONEY BEES (APIS
MELLIFERA) INFESTED WITH NOSEMA APIS
J. Kralj, S. Fuchs, J. Tautz
National institute of Biology, Slovenia

> Varroa destructor, a major pest of honey bees, alters flight behavior of foragers to a degree that may prevent their successful return to the colony. Infested workers have impaired orientation and need more time to return to the colony. As V. destructor is a relatively recent pest of the western honey bee Apis mellifera and thus specific adaptations can not be expected, it would be possible that the behavioral response is more general in nature. Here we tested the flight behavior of foragers infested by Nosema apis. Sampling departing and returning bees at the entrance showed lower infestation of returning workers compared to departing workers indicating higher loss of infested bees. Infested workers took 1.7 times longer to return to the colony than uninfested workers when released from the same location. Prolonged flights were also confirmed by labeling workers with radio frequency identification tags (RFID) to register their departure and return at the colony entrance. This data also showed that infested workers had shorter life spans and vanished from the colony earlier. The study shows a similar effect of parasitism on flight behavior of foragers infested by N. apis to that shown for V. destructor suggesting that the altered flight behavior of foragers is a general response by diseased bees and it is not limited to infestation by V. destructor. This behavior can be interpreted as *suicidal pathogen removal*, serving as a disease defense mechanism which reduces the colony's load of parasites or pathogens.

in Proceedings of the Second European Conference of Apidology EurBee

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