Droning on again…

With “queen problems” reported as a leading issue contributing to beehive loss, Dave Black asks, are we paying enough attention to the other half of the equation: our drone stocks? The well-read Bay of Plenty beekeeper seeks out research on the subject, uncovering some intricacies of the drone bee and knowledge for better hive management.

However you cut it, in New Zealand beekeepers report around 10% of colonies as winter losses each year. Every year 30-35% of those lost is described as attributable to ‘queen failure’[1]. Managed queen replacement to maintain hive performance is common practice among New Zealand beekeepers, especially large operators, of whom about half report a regular requeening programme. That’s besides the usual loss as supersedure, and what about the lack of vigour, diversity and cohesion that provides an opportunity for whatever is going around to, er, come around. We have to wonder whether something can be done about that. Is that just Nature, was it ever thus? Even if it is, can we not still try to improve the odds and leave less to chance? Can we reliably tell if a queen is failing?

A drone and queen bee mating on the wing. While beekeepers pay special attention to the queens that keep their hive ticking over, should drones be given more attention for the critical contribution they make to hive health and longevity?

Many beekeepers, especially the ones who can’t find their queens, use brood pattern as a proxy for queen quality. A ‘poor’ brood pattern is clear, defined as more than 20% of the cells vacant[2], and is the queen’s fault, whereas a ‘good’ pattern is… well, better than a poor one. A US study a couple of years back pointed out that there wasn’t any reason to suppose we could be quite so definitive[3], plenty of things disrupt brood laying. They measured queens from 76 ‘poor’ and ‘good’ colonies for head width, thorax width, and live mass, and the percentage of live sperm out of the total sperm counted. None of these measurements was reliably associated with either pattern, and nothing else seemed any different either. In a second year they also swapped queens over, that is, the assessed ‘good’ queens were introduced into the ‘poor’ colonies, and the ‘poor’ queens went to ‘good’ colonies. Counterintuitively, the ones with ‘good’ patterns got worse, and the ‘poor’ ones got better. It looks like brood patterns could be a team game and not a royal prerogative.

The individual attribute we use most to choose a good quality queen is probably size. We mean weight. While science can’t point at any particular dimension and it’s true the studies differ in detail, the overall empirical conclusion is that weight correlates closely with ovary mass and the number of stored sperm. Biggest is best. Unable to look inside a queen, the only useful internal metric the rest of us have is the colour or size of the spermatheca which can only be gauged posthumously. It’s worth noting that these are usually only half full[4], even in ‘good’ queens.

A frame of drone brood, but how viable will the inhabitants be in later life?

Half-full of what is the obvious question. Very little is known about honey bee sperm quality, perhaps because it’s unusual compared to other domestic animals and needs distinct study techniques[5]. Its structure makes quite hard to count and it’s difficult to spot abnormalities. It tends to ‘clump’ which makes extrapolating a small counted area to a larger volume perilous. There isn’t much of it so measuring density is not straightforward. Even in a healthy drone the number of sperm produced may vary according to body weight, age, season, and genetic factors so the range of results is wide. Sperm production seems to peak in large, autumnal, 21 day old drones, but good estimates are difficult to achieve.

Even if we can count it, is it healthy? Sperm viability can be assessed but we have to take account of a natural attrition as it moves from being kept alive by its seminal fluid, mixed with competing males’ seminal fluid, to support in spermathecal fluid. There is good evidence for ‘cryptic female choice’ with spermathecal fluid differentially favouring the success of particular types of sperm. So far other important aspects of sperm health have defied routine examination.

As little as 5% of all the sperm the queen receives from multiple males ends up stored[6], for years, in the spermatheca, and yet it’s central to the survival of the colony. It’s easy to get tied up by what we don’t know. A great deal of thought goes into the production of good queens, and despite the knowledge gap about the male contribution, that has to be matched by producing good strong drone mother colonies. Experience tells us what these have to be like; our get-out-of-jail card is lots of big, diverse drone mother colonies. Headed by older queens, with good stable weather and an abundant, continuous pollen supply we can have drones that contribute 5% of something good.

Dave Black is a Bay of Plenty based hobbyist beekeeper who now works in the kiwifruit industry. He has a degree in environmental science and for the past 25 years he has been reading and writing about bees and beekeeping. His essays are available at https://beyondbeebooks.substack.com/

[1] MPI Biosecurity New Zealand Colony Loss Surveys, 2015-2020. https://www.mpi.govt.nz/biosecurity/plans-for-responding-to-serious-disease-outbreaks/bee-biosecurity/bee-colony-loss-survey/ Accessed January 2022 [2] vanEngelsdorp, D.; Tarpy, D.R.; Lengerich, E.J.; Pettis, J.S. Idiopathic brood disease syndrome and queen events as precursors of colony mortality in migratory beekeeping operations in the eastern United States. Prev. Vet. Med. 2013, 108, 225–233 [3] K. V. Lee, M. Goblirsch, E. McDermott, D. R. Tarpy, and M. Spivak, “Is the brood pattern within a honey bee colony a reliable indicator of queen quality?,” Insects, vol. 10, no. 1, pp. 1–17, 2019. [4] David R. Tarpy, Jennifer J. Keller, Joel R. Caren, Deborah A. Delaney, Assessing the Mating ‘Health’ of Commercial Honey Bee Queens, Journal of Economic Entomology, Volume 105, Issue 1, 1 February 2012, Pages 20–25, https://doi.org/10.1603/EC11276 [5] Jesús L. Yániz, Miguel A. Silvestre and Pilar Santolaria. Sperm Quality Assessment in Honey Bee Drones, Biology 2020, 9, 174; doi:10.3390/biology9070174 [6] B. Baer, J. Collins, K. Maalaps, and S. P. A. Den Boer, “Sperm use economy of honeybee ( Apis mellifera ) queens,” pp. 2877–2885, 2016.


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