Selection and breeding

We continue our journey through the latest and most important knowledge about the male component of the hive, which not only has always been unrecognized and disparaged, but has often even been prevented from reproducing, or playing its crucial role. We are talking about the drones, which in the previous article we boldly named them, with a deliberately provocative and reductive simplicity, spermatozoids with wings. We have shared with you aspects that make them be noticed completely differently, to be appreciated and valued: behaviours, phases, conditions, difficulties they encounter in their process of coming-of-age and sexual efficiency, the duration of their first orientation flights, types of penetration into the assembly areas – DCA -, the predilection to carry out their function near the colony from which they come.
However, regarding the characteristics of their flight activities we have limited ourselves to mentioning the extraordinary speed – 30 km/h – but their motor skills are an important and fundamental aspect of the entire biological cycle of bees. Flight is the basis of the specific ethology of drones, and its characteristics have been a mystery until now, when we finally begin to discover and know them. An ability of the male component that should lead us to reposition on the scale of importance what until recently was shrouded in an aura of mystery and depreciated mostly due to apparent uselessness, but which, in light of recent discoveries acquires a fundamental role in understanding the evolution and genetic specialization of bees in order to measure and try to develop effective breeding strategies, having another consideration towards the complex biology of the animal we grow up.

The flight of drones, recent information

There are two types of flight of the male component of the bee colony: that of young drones, short flights, called “orientation” and those of adult males, longer, called “fertilization”, to attend the congregation areas – DCA – (Witherell 1971, Currie 1987). The first orientation flights are carried out in the first 6/9 days after birth; the purpose is to acknowledge the territory around the hive, to train and improve the flight capabilities, to improve the return performances in the own nest (Capaldi 2000). Drones perform an average of 8/9 orientation flights during their lifetime (normally 3 per day), lasting about 15 minutes each, the first one being in the immediate vicinity of their hive, after which they begin to wander off, but never to more than a few hundred meters from the hive they come from. It has been shown that drones that dedicate more time to orientation flights, then stay longer in the DCA (Capaldi 2000). Orientation flights therefore have a fundamental role in training and learning.
As well as the bees, part of the drones also dies in the field and therefore does not return from flight. The study found that between 70 and 80% of males return to their nest (Reyes 2019). Despite the misconception, when returning from these flights, drones generally remain faithful to their hive: it happens very rarely that they migrate to other colonies, respectively in only 20% of cases (Koeniger 2005).

As a result of the effort during orientation flights, there is a long period of inactivity ranging from 5 to 12 days (depending on the season), during which drones remain inside the hive until the age of 21 days in spring and 14 days summer.
The drones then start their first fertilization flights, with an average duration of 30 minutes each, from 2 to 5 flights per day, with a total ranging from 14 to 22 fertilization flights over the entire life of a drone. The drone can visit several DCA in one day (Ruttner 1966) and between flights it rests in the hive and regains its strength by eating honey (Currie 1987). The stay time inside the hive between two fertilization flights is 3-4 minutes; in contrast, the total stay time inside the DCA (estimated based on the total duration of the flights) is 510 minutes in spring and 327 minutes in summer.
The flight activity of drones is highly conditioned by: weather conditions, temperatures, time and season. In general, they start flying in the afternoon, between 2 pm and 6 pm, the peak of their activity being reached around 4 pm, and in summer, the flight period is extended by 3 hours compared to spring; flights were recorded, in favourable weather conditions, even in the morning, from 7 am to 9 am and late in the evening, from 7 pm to 10 pm (Fukuda and Ohtani 1977). The minimum temperature for a good flight, as duration, radius, etc. is 19 degrees.
Drones are extremely sensitive to high temperatures and in the summertime, there is a much lower longevity of the drone due to increased flight activity, extreme weather conditions and colony stress. The maximum age of a drone recorded in summer is 23.5 days compared to 33 days in spring (Wintherell 1972). Also, if the wind speed is higher than 30 km / h, drones (of any age) rarely venture outside the hive: under these conditions there are very short flights in the immediate vicinity of the hive, but they are “purification” flights (Page and Peng 2001).

An extremely interesting scientific study, conducted in 2019 by Maritza Reyes and others, began to represent and describe the phenomenon that until recently was shrouded in mystery and which is actually fundamental to better understand the reproduction of bees, trying, therefore, to measure itself in order to develop effective growth and selection strategies; it started from a different appreciation of the hive biology, more precisely from the way in which the flight activity of drones influences mating and reproduction. The study was conducted over an entire season, using a very high-resolution video camera with an optical lens that recognizes marked drones and monitors their input and output activity from the hive, providing extremely accurate and surprising data. The average total duration of periods spent ”outside the house” by a drone is 7 hours and 37 minutes in spring and 6 hours and 19 minutes in summer. The footages performed over the course of two years of the study proved that the total number of orientation and fertilization flights carried out during the life of a drone is on average 20-27, with an observed maximum of 106 and a minimum of 1: this it is due to the fact that in spring 48% and in summer 19% of drones do not live long enough to be able to perform fertilization flights..

The closer, the better

Although there has been recorded the presence in the congregation areas – DCA – of some drones coming from colonies located 5 km away (Ruttner 1971), and although the longest flight ever recorded by a drone was 2 hours and 51 minutes, from the exit to its entrance in the hive (Reyes 2019), all scientific studies designed to determine the distance of the congregation areas from the home hives of male have shown that they are positioned mainly within a radius of 200 m to 2 km , most often within a radius of 200 to 400 meters (Koeniger 2005, Galindo-Cardona 2012). A drone visits numerous DCA during its lifetime: it ”trains” to be competitive in the heap of fertilization comets. The possibility of affirmation in the ”pole position” depends on: speed, sprint, sufficient ”fuel”. In general, however, it chooses for reproduction the areas closest to the hive from which it originates (Koeniger 2005). On the other hand, the average duration – 30 minutes – of fertilization flights (from when the drone exits until it re-enters the hive), confirms that the DCA distance chosen by the drones is generally 200-800 meters from the colony from which it originates (Reyes 2019, Galindo-Cardona 2012).

This is due to obvious and concurrent reasons:

1. the “energy saving” priority that would allow it to stay longer in the DCA and increase its chances of gaining a dominant position in fertilization comets,
2. drones (like bees, by the way) orient themselves and can better recognize differences and changes in the horizon line within a radius of 200/400 m from the hive.

These extremely interesting scientific data propose a specific genetic characterization of colonies that remain within a certain territorial radius, related to the different aggregations of drones in the same area. There are therefore genetic differences, which we might consider as being interesting or even valuable, between groups of bee colonies (populations that have often developed through environmentally stimulated interactions and zootechnical management) and the respective and different DCA (Koeniger 2005).

The specific characteristics of drone flight activity are one of the fundamental elements of the reproductive characteristics of Apis mellifera. These peculiarities facilitate the genetic adaptation of bees and the extraordinary spread of this species in such different areas of the planet. Now more than ever, both the bee and the environmental contexts in which it survives, are subject to new epochal transformations.
Reconfiguring the role and biological importance of drones is one of the keys, in an attempt to develop a series of effective breeding, reproduction and selection strategies. In terms of bee breeding, the time has come to try to go beyond the limits of the anthropocentric approach, in an attempt to renew zootechnical management to also make use of the ability of drones to do… what they know how to do… pretty good even!