Differential Viral Distribution Patterns in Reproductive Tissues of Apis mellifera and Apis cerana Drones

Honeybee drones are male bees that mate with virgin queens during the mating flight, consequently transferring their genes to offspring. Therefore, the health of drones affects the overall fitness of the offspring and ultimately the survivability of the colony. Honeybee viruses are considered to be a major threat to the health of honeybees. In the present study, we demonstrated the pattern of common honeybee viruses in various tissues of drones in the western honeybee, Apis mellifera, and the eastern honeybee, Apis cerana. Drones were collected during the mating flight and analyzed using quantitative real-time (qRT-PCR) to detect the presence of seven honeybee viruses. The qRT-PCR result revealed that three honeybee viruses, namely Black Queen Cell Virus (BQCV), Deformed Wing Virus (DWV), and Chinese Sacbrood Virus (CSBV), were detected in the reproductive tissues of A. mellifera and A. cerana drones. The results from qRT-PCR showed that the Israeli Acute Paralysis Virus (IAPV) was only detected in A. mellifera drone body tissues. Moreover, the prevalence of DWV and BQCV in the drones collected from A. mellifera colonies was significantly higher than that of A. cerana. In addition, virus multiple infections were higher in A. mellifera drones compared to those in A. cerana. CSBV was found predominantly in the reproductive tissues of A. cerana drones. This study is the first report describing the presence of the CSBV in reproductive tissues of A. mellifera drones. Our results may reflect the preference of honeybee viruses in honeybee species and may provide a piece of interesting evidence for understanding the virus transmission in A. cerana.

The Song of the Queen

The mating flight of a honey bee queen is orchestrated by events that occur days before she actually flies from her nest in pursuit of a gathering of drones, 20 or so of which will get lucky and mate with her. Her mating song begins within the nest while she’s still held captive in her royal cell by her worker sisters, piping and tooting audible sounds to her rival queens and her captors. The song changes pitch and intensity after she’s released from captivity and seeks out and destroys her rivals. The orchestra is joined by the workers running through the nest buzzing their wings, exciting the colony and the new virgin, pushing her toward the entrance, where she takes flight. When she finds the congregation of drones, they join in with the buzzing of their wings and popping sounds of their genitalia as they find and mate with her. The queen returns to the nest, the heir of the nest and colony; and a new superorganism is born.

Balling Behavior of Workers Toward Honey Bee Queens Returning from Mating Flights

During natural mating honeybee queens can get lost due to drifting, predators or other cases. In this work, the balling of queens returning from flights by worker bees originating from the same colony was observed. Three subspecies of bees Carniolan, Caucasian and European Black Bee were tested. Research was conducted in both spring and summer, but in the former in newly created colonies, while in the latter in new and earlier used ones. Generally 15.2% of queens were balled and in total 30.2% of queens were lost during mating flights. 269 queens performed 785 mating flights, and 5.2% of those finished with balling. Three times more queens were balled when returning from mating flight rather than orientation flight. Subspecies matches or mismatches of queens and workers in nucleuses did not significantly affect the balling or its frequency. Additionally, no bee subspecies characterized stronger tendencies to ball a queen. Worker bees from newly created nucleuses treated queens similarly to the ones in nucleuses earlier used. However, significantly more queens had been balled during the spring in comparison to summer. There were days with higher balling of queens. During some days the weather was very unstable and unpredictable with such anomalies as heat waves, thunderstorms or sudden drops in insolation. Most of the queens were balled at the entrance while returning from flight and only a few inside the hive. In the research, clear causes of balling were not found, but some factors can be excluded.