insects Review Neuroethology of the Waggle Dance: How Followers Interact with the Waggle Dancer and Detect Spatial Information Hiroyuki Ai 1,* , Ryuichi Okada 2, Midori Sakura 2, Thomas Wachtler 3 and Hidetoshi Ikeno 4 1 Department of Earth System Science, Fukuoka University, Fukuoka 814-0180, Japan 2 Department of Biology, Kobe University, Kobe 657-8501, Japan 3 Department of Biology II, Ludwig-Maximilians-Universität München, Planegg-Martinsried 82152, Germany 4 Department of Human Science and Environment, University Hyogo, Kobe 670-0092, Japan * Correspondence: [email protected] Received: 1 September 2019; Accepted: 6 October 2019; Published: 11 October 2019 Abstract: Since the honeybee possesses eusociality, advanced learning, memory ability, and information sharing through the use of various pheromones and sophisticated symbol communication (i.e., the “waggle dance”), this remarkable social animal has been one of the model symbolic animals for biological studies, animal ecology, ethology, and neuroethology. Karl von Frisch discovered the meanings of the waggle dance and called the communication a “dance language.” Subsequent to this discovery, it has been extensively studied how effectively recruits translate the code in the dance to reach the advertised destination and how the waggle dance information conflicts with the information based on their own foraging experience. The dance followers, mostly foragers, detect and interact with the waggle dancer, and are finally recruited to the food source. In this review, we summarize the current state of knowledge on the neural processing underlying this fascinating behavior. Keywords: honeybee; waggle dance; distance information; brain; antenna-mechanosensory center; vibration; sensory processing; standard brain; computational analysis; polarized light processing 1. Behavioral Significance of the Waggle Dance The honeybee (Apis mellifera) is well known to possess the ability to communicate to its nestmates to convey the locational information of a profitable food source she has visited [1]. Once a scout bee has found a profitable food source and returned to the hive, she will perform a dance (round dance or waggle dance for a short or long distance food source, respectively) to recruit new bees to visit the food source (Figure1). During the waggle dance, the bee runs relatively straight with her body waggling (a waggle run) and circles back to the starting point of the waggle run without wagging or wing-beating (the return run). On the vertical comb, the direction to a food source from the hive relative to the sun’s azimuth is encoded according to the angle between the upward direction and the waggle run direction, and the distance from the hive to the food source is related to the duration of the waggle run [1]. Bees in close proximity to the dancing bee (followers) receive this information, and some of them may be recruited to the same food source, with many foragers ultimately visiting there [2]. Insects 2019, 10, 336; doi:10.3390/insects10100336 www.mdpi.com/journal/insects Insects 2019, 10, 336 2 of 16 Insects 2019, 10, x 2 of 15 Figure 1.1. TheThe wagglewaggle dance. dance. (A ()A A) dancerA dancer (arrow) (arrow) on theon wagglethe waggle run and run many and beesmany (followers) bees (followers) around thearound dancer. the dancer. (B) Encoding (B) Encoding a direction a direction of a food of source.a food source. 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