Queen mating flights—how many, how long, how to gauge sufficiency….

[susan rudnicki]

One of my students asked me how long the mating flight lasted and I did not know. Here is some really interesting data from a experiment carried out by
Nikolaus Koeniger, Gudrun Koeniger at University of Frankfurt and written up in 2007 of Apidologie

1. INTRODUCTION To raise and maintain a sound and reproductive successful colony, honeybee (Apis mellifera L.) queens require a large storage of sperm in the spermatheca ranging from 2 to 6 million. About 5 to 10 days after emergence, young queens leave their hives for mating and, after one or two short orientation flights (from 1 to 2 min), they visit drone congregation areas (DCA, as rendez vous places in honeybees are named). There they copulate with several drones, which deposit their sperm in the queen’s oviducts. Back in the colony less than 5% of the received sperm is transferred from the oviducts into the queen’s spermatheca. This filling process takes more than 24 hours (Woyke, 1960, 1988). Woyke (1960) measured the sperm volume in the oviducts from 129 reCorresponding author: N. Koeniger, Nikolaus.Koeniger@bio.uni-frankfurt.de * Manuscript editor: Stan Schneider turning queens. On average the volume was equivalent to that of 10 to 12 drones. Other authors analyzed patrilines of the offspring and estimated between 5 and 10 copulations during one flight (Franck et al., 2002; Schlüns et al., 2005a). Queens regularly fly 1 to 2 km to reach a DCA (Ruttner and Ruttner, 1972). The time to reach the DCA and the highly polyandric mating system in the honeybee involves costs and risks for the queen. Since queens are not able to mate again and replenish their sperm storage once oviposition has started, a behavioral control of mating success has a high evolutionary significance. Mating flights in general last from 10 to 30 min (Ruttner, 1954). About 60% of the queens perform two mating flights and 10% fly out more often (Woyke, 1964). Similar results were published by Schlüns et al. (2005a). In experiments of Tarpy and Page (2000), however, only 27% of the queens (8 queens out of 30) had more than one mating flight. Due to predation, weather conditions, mistakes in
relocating the colony and several other causes, 10% to 20% of queens are lost during these flights (Ruttner, 1980; Ratnieks, 1990; Schlüns et al., 2005a). Queen loss during mating is disastrous for a bee colony. The old queen has already left the nest together with a swarm before emergence of young queens and the sexual maturation of a young queen takes at least 5 days. Thus, at the time of the queen’s mating flight the female larvae in the nest are too old to be transformed into new queens. Queen loss during mating flights therefore results in the inevitable death of the colony. Limitation of number and duration of mating flights by the queen to an optimum would minimize the mating risks and increase her fitness. Woyke (1964) suggested that queens adjust their nuptial flight frequency to the amount of sperm from the previous mating flight. He proposed that the queen’s behavior is influenced either by the amount of sperm in the oviducts or by the concentration of spermatozoa in the spermatheca. Schlüns et al. (2005a) analyzed the number of patrilines after one flight. Queens which tried to perform additional mating flights (but were hindered from doing so) had significantly less copulations and tended to have fewer spermatozoa in the spermatheca than queens that started oviposition without further flights. They suggest that the queen “counts” the number of copulations “to decide” whether or not an additional mating flight is required. Both findings support the hypothesis that queens are able to adjust their behavior according to the mating success of a previous nuptial flight. Tarpy and Page (2000), however, did not find a correlation between mating flight duration and frequencies of copulation or mating flights, respectively. They concluded that there is no behavioral control by queens, neither by adjusting flight duration nor by taking extra mating flights. Our experiment was designed to extend the queen’s flight time required to contact a suffi- cient number of drones. In an isolated Alpine valley, we adjusted the number of drones to 2.500 drones which was about 25% of the previous years (Koeniger and Koeniger, 2005) and we monitored the duration of one mating flight. Later, we counted the number of spermatozoa in the queen’s spermatheca and compared this to her flight duration. In case queens tend to copulate with as many drones as possible, sperm numbers in the spermatheca should increase with the duration of mating flight (positive correlation). A “no correlation” between flight duration and sperm numbers may have several causes. A negative correlation between mating flight duration and sperm numbers would support the idea that queens continuously get information on her mating success during the nuptial flight and return to the colony as soon as they have mated with a sufficient number of drones.

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