Animal Science

Biometric parameters of newborn drones of honeybee (Apis mellifera L.) and factors that affect them, in hives from Mayabeque, Cuba

0000-0002-6892-6817Leyanis Ocaña¹  , 0000-0002-7835-1279Anisley Pérez¹  , 0000-0003-4745-0589Tamara Fernández¹  , 0000-0003-3115-9885J. Demedio^{1  *} 

¹Universidad Agraria de La Habana “Fructuoso Rodríguez Pérez” (UNAH). Apartado Postal 18-19, CP 32700, San José de Las Lajas, Mayabeque, Cuba

Abstract

In order to determine biometric parameters of newborn drones of Apis mellifera L. and factors that affect them, a study was conducted in three apiaries from San José de las Lajas municipality, which included a monthly sampling of 10 hives/apiary, in November and December, 2015 and in January, 2016. An amount of 50 newborn individuals were examined, and their birth weight and body length were determined, as well as their fore right wing and body color. Infestation extension and intensity by Varrea destructor was evaluated. Weight and dimensions of drones were in correspondence with those of European breeds, and were influenced by the apiary of origin, sampling month and intensity of infestation.

Key words: Apis mellifera; drones; biometrics; varroosis

The honeybee (Apis mellifera L.), as a pollinating insect, plays an essential role in ecosystems. Approximately 90% of wild plants and a third of food plants consumed by humans depend on their pollination. It has been estimated that the economic value of bee pollination, for agriculture alone, could be around US $ 500 billion annually worldwide. This activity represents an important source of food and natural medicines for humans, without underestimating the commercial value of honey, wax, pollen, propolis and royal jelly (^{MITECO 2019}).

In Cuba, the technology of pollination of crops with bees is hardly practiced, and the fundamental objective of beekeeping is to obtain the products of the hive, especially honey. Its importance as an export-generating activity has promoted cutting-edge technical advances worldwide, based on the professionalism of beekeepers, land use planning and integrated health management, which excludes the use of drugs and has developed, for years, a national genetic selection and improvement program (^{MINAG 2002}, ²⁰¹³ and ^{Pérez-Morfi and Pérez-Piñeiro 2018}).

This progress has been made with a hybrid bee from European breeds, especially A. mellifera mellifera and A. mellifera ligustica, despite the presence of the dangerous mite Varroa destructor for 25 years. However, the possibilities of its improvement are not exhausted and the risk of introduction of the Africanized bee is permanent, and not only accidental, so it constitutes an environmental, social and economic threat that requires constant monitoring. Morphometric studies are quick and effective diagnostic methods to discard the presence of these bees, especially in Cuba, which is surrounded by territories where these highly defensive hybrids, with great expansion power, exist (^{Moreira et al. 2017}, ^{Graciano 2018} and ^{Urbina et al. 2019}). Despite speculation about its presence on the island (^{Galindo-Cardona 2013}), there is no report that supports this assumption.

Drones provide the highest percentage of genotypic and phenotypic characteristics. They develop in cells larger than the workers, and are born 24 days after laying. For them, the queen bee breeding center is key, of which there are more than 60 in Cuba (^{APICUBA 2019}). However, these drones have received little attention from the research point of view (^{Bande et al. 2008} and ^{Ocaña-Nápoles 2014}). European drones have a very bulky body and their weight can reach 230 mg, and between 15 and 17 mm in length (^{Pasini and Falda 2003}). The Africanized ones are smaller (^{Guzmán-Novoa et al. 2011}), but faster. They are present throughout the year and produce almost 30% more sperm (^{Hernández 2019}).

It has been reported that among the most important environmental factors that can reduce size and weight of bees at birth is the decrease in the capacity of brood cells due to aging of honeycombs (^{Sanabria et al. 2015}) and parasitization by Varroa destructor mite during the capping period (^{Guzmán-Novoa and Correa 2012} and ^{Ramsey 2018}). Although Cuba has maintained an efficient program for the integrated management of bee health for years, which excludes the use of chemical treatments (^{APICUBA 2019}), varroosis continues to be the main problem worldwide (^{OIE 2015}). From this background, this research set out to determine biometric parameters of drones at birth and the factors that affect them.

Materials and Methods

The study was developed in three apiaries in Mayabeque province. One from San José de las Lajas municipality (SJ) and two from Tapaste town (T1 and T2), belonging to this municipality. SJ apiary is an auxiliary apiary of the Centro de Cría de Reinas “Los Pinos” (CCR, in Spanish). It has 20 hives with two bodies, in good condition, which supply honeycombs with pollen or brood when required. T1 and T2 apiaries have maintained a composition of 20 hives each, which objective is honey production.

Although these apiaries yielded a mean productivity of 40 kg/hive, the state of their brood chambers showed blackened honeycombs due to aging. These apiaries were chosen for not being sources of infectious diseases and for having access and protection facilities. The annual change of queens takes place in all hives.

From each apiary, 10 hives were analyzed, in two bodies and with a good strength state. As a requirement, hives had to have a brood of drones with pink eyes, about four or five days after hatching. In each hive, the diameter of the cells of drone was measured and a honeycomb fragment (10x10 cm) of this brood was cut for transfer to the laboratory and to conclude its development in an incubator.

A total of 50 drones per hive were evaluated at birth. A monthly sampling was carried out during November and December 2015 and January 2016. Body length (LZ) and forewing, weight (PZ), color and extension and invasion intensity (E.I. and I.I.) were determined to newly emerged drones for Varroa destructor. For this, the surface of individuals and the interior of the corresponding cells were examined in a stereoscopic microscope.

Cell diameter. One honeycomb per one of the 10 analyzed hives from the center of the brood chamber was selected. An amount of 10 cells were measured on both sides in line to average and reduce the error to result in four measurements per hive. Measurements were carried out with a special methodology of the program for controlling the Africanized bee (^{SARH-USDA 1986}).

Drone length. A mechanical Vernier caliper was used to determine body length of drones.

Right forewing length. A group of 25 drone wings were taken per hive. They were detached with the fingers and fixed with transparent commercial enamel on slides on each sheet, and measured with the aid of the caliper.

Weighing. The analyzed drones were numbed with ether and individually placed with the help of a tweezers on a Sartorius scale, BSA 124S model, on filter paper.

Coloration. It was carried out by visual appreciation and the criteria of ^{Pérez Hernández (2009)} were considered, which establish the categories of drones: with totally yellow (A), totally black (N) and intermediate (I) segments. The latter are yellow in one or two segments.

Invasion extent and mean invasion intensity by V. destructor. A 10x10 cm honeycomb fragment was cut from each hive, with young in the pupal stage (16-17 d of age). They were brought to the laboratory in identified glass flasks, with perforated lids (^{NC 2010}). They were placed in 30x20x10 cm cardboard boxes and placed in a total visibility incubator (Stuart Scientific Incubator SI60) at 34^oC. At the beginning of the hatching process, cells were opened and the interior and drones were examined with the help of a tweezer and a simple magnifying glass with 4x magnification. These indexes were calculated following ^{Verde et al. (2013)} using the following formula:

$\mathrm{M}\mathrm{e}\mathrm{a}\mathrm{n}\mathrm{ }\mathrm{i}\mathrm{n}\mathrm{v}\mathrm{a}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{ }\mathrm{e}\mathrm{x}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{ }\left({\mathrm{E}.\mathrm{I}.}_{\mathrm{m}}\right)\mathrm{ }=\mathrm{ }(\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{a}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{d}\mathrm{ }\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}\mathrm{s}/\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{e}\mathrm{x}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{d}\mathrm{ }\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}\mathrm{s})\mathrm{ }\mathrm{x}\mathrm{ }100$

$\mathrm{M}\mathrm{e}\mathrm{a}\mathrm{n}\mathrm{ }\mathrm{i}\mathrm{n}\mathrm{v}\mathrm{a}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{ }\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}\mathrm{ }\left({\mathrm{I}.\mathrm{I}.}_{\mathrm{m}}\right)\mathrm{ }=\mathrm{ }(\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{m}\mathrm{i}\mathrm{t}\mathrm{e}\mathrm{s}/\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{ }\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{a}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{d}\mathrm{ }\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}\mathrm{s}).$

Data was processed by Statgraphics, version 5.1 (^{Statistical Graphics Corp 2000}):

• Descriptive statistics, for morphometric indicators and infestation indexes

• Comparison of means for the weight of parasitized and non-parasitized drones

• Multiple range test (^{Duncan 1955}) to compare all biometric parameters among the three apiaries

• Simple regression analysis (cell diameter - PZ; I.I. - PZ; I.I. - LZ).

To compare the percentage values, a comparison of proportions was performed (Compaprop).

Results and Discussion

Mean diameter of cells in SJ apiary was superior to that of the commercial apiaries (table 1). As in addition to geographical proximity, most of the queens of the latter come from the CCR, it is unlikely that this difference and that between the T1 and T2 apiaries is due to genetic factors. Rather, it can be attributed to the way bees are forced to build these cells. In the CCR, drone rearing is favored in parental hives with naturally manufactured drone combs. However, in commercial apiaries, this type of cell is built on sheets for workers of less stamping and less, in lower marginal areas of these combs.

Table 1 Mean diameter of drone cells in the three apiaries 

Indicators	SJ apiary	T1 apiary	T2 apiary
Number of cells, N*	40	40	40
Means, mm	6.77^a	6.48^b	6.61^c
SD	0.16	0.36	0.31
SE ±	0.02	0.06	0.05
CV (%)	2.33	5.64	4.62

* Each measuring (40) corresponded to four segments of 10 cells

Multiple range test (^{Duncan 1955}): P ˂ 0.05

Different letters indicate significant differences

These measures could be taken as a baseline for comparison in the absence of antecedents. Although reduction and variability has been reported in the diameter of worker cells, when bees are induced to work on sheets that do not have their own stamping dimensions (^{Hall et al. 2015} and ^{Sanabria et al. 2015}), cell by cell measurement and knowing its origin is required, as well as more precise instruments. The external diameter has, in addition of an identifying value, the advantages of being a highly heritable genetic trait, like other morphological ones (^{Guzmán-Novoa 2012}) and easy to measure. Meanwhile, the environmental influence on cell capacity, caused by aging and the accumulation of residues in each rearing cycle, has been routinely evaluated based on the management of the rearing chamber and the coloration of combs (^{Verde et al. 2013}).

Body mean lengths drones at birth (table 2) are between 15.40 ± 0.70 mm and 15.57 ± 0.66 mm, the highest value corresponding to samples obtained from the SJ apiary.

Table 2 Mean length of drone body at birth, in each apiary 

Indicators	SJ apiary	T1 apiary	T2 apiary
Number of drones, n	1 028	982	1 006
Mean length, mm	15.57^a	15.40^b	15.44^b
SD	0.66	0.70	0.70
SE±	0.020	0.022	0.022
CV, %	4.26	4.52	4.53

Multiple range test (^{Duncan 1955})

Different letters indicate significant differences (P ˂ 0.05)

There is little history of this indicator in drone rearing. ^{Arias et al. (2006)} reported a range of 15-17 mm in hives in Spain, in which the values of the present study are included. ^{Ocaña-Nápoles (2014)} determined, in the same area, a minimum value of 14 mm in yellow and intermediate color flying drones, and a maximum of 18 mm, in intermediate and black ones. These results agree with the European origin of the Cuban native bee (^{Pérez-Morfi and Pérez-Piñeiro 2018}) and show no clear difference between months. On the other hand, the effects overlap, so that samples for each month, to a large extent, must correspond to cells taken in the previous month, a fact that is often obviated when trying to establish cause-effect relationships.

The greater mean body lengths of drones in the SJ apiary in comparison with the T1 and T2 apiaries contribute to the greater dimensions of cells and a better zootechnical management in the former. T1 and T2 apiaries are the subject of poor zootechnical attention, appreciated in the darker and aged combs. This factor results in a reduction in the size of individuals raised in their cells. A similar effect was manifested in wings and has been recognized in the breeding of workers (^{Verde et al. 2013}). In this same SJ apiary, ^{Pérez-Hernández (2009)} determined means of 5.37 ± 1.5 mm and 5.35 ± 1.1 mm in cells of workers, all in correspondence with values ​​described for European bees. When analyzing the factors that influenced these results, these authors refer to honeycomb aging as the main environmental component that reduced the dimensions of the emerging individuals. However, a similar effect cannot be discarded, reported by ^{Hall et al. (2015)} in cells infested by V. destructor.

In the same way that cell dimensions (^{Sanabria 2007}) are influenced by the fact that the bee must act on sheets with different patterns to their measurements, their cells do not correspond to the natural ones (^{Sanford and Hall 2005}). In the SJ apiary (CCR), drone cells are found in naturally constructed combs, without having stamped sheets as a base. This helps to explain why they reach larger dimensions with respect to commercial apiaries (T1 and T2).

When comparing the results in the three months of study, differences were appreciated between December and January. However, both months did not differ from November (table 3), which is attributed to the age of the combs.

Table 3 Mean length of drones per months 

Statistics	November	December	January
Number of drones, N	980	991	1 045
Mean length, mm	15.48^ab	15.49^a	15.42^b
SD	0.72	0.67	0.68
CV, %	4.64	4.30	4.43

Multiple range test (^{Duncan 1955})

Different letters indicate significant differences P ˂ 0.05

^{Pérez Hernández (2014)} observed that the forewing length of Cuban worker bees (9.55-9.70 mm) exceed those reported for American ecotypes of European ancestors (^{Uribe et al. 2003}), which confirms the first and most important observations made in Cuba (^{Díaz-Millán 1981}). Similar performance is to be expected in drones, clearly larger than Africanized ones. Despite the high heritability of this trait (^{Guzmán-Novoa 2012}), possible environmental influences are not excluded, especially the aging of the brood chamber and the reduction of body and its appendages (^{Verde et al. 2013} and ^{Hall et al. 2015}).

Table 4 shows the mean length of the right forewing between 11.31 ± 0.46 mm and 11.37 ± 0.48 mm, without a significant superiority, in the SJ apiary.

Table 4 Mean length of the right forewing of drones at birth per apiaries 

Indicators	SJ apiary	T1 apiary	T2 apiary
Total wings	500	500	500
Mean length, mm	11.37	11.35	11.31
SD	0.48	0.48	0.46
SE ±	0.021	0.021	0.021
CV, %	4.24	4.21	4.10

Multiple range test (^{Duncan 1955}): P ˂ 0.05 (n.s.)

In Cuba, there is no history of published studies, in which wing dimensions of drones are determined. ^{Díaz-Millán (1981)} carried out the most extensive and documented morphometric evaluations in Cuba, but all were conducted in worker bees. Studies of ^{Voroshilov (2008)} and ^{Pérez Hernández (2014)} did not considered the males either. It is significant that, in all these studies, the wings of workers reached dimensions in the range of those of Europe (^{Arias et al. 2006}) or exceeded them. This result contributes to refute the speculation about the presence of the Africanized bee in Cuba (^{Galindo-Cardona 2013}).

The mean weight of drones at birth (table 5) is between 190.67 mg and 200.13 mg, with the lowest values in the T1 apiary and the tendency to supremacy in SJ.

Table 5 Mean weight of drones at birth per apiaries 

Indicators	SJ apiary	T1 apiary	T2 apiary
Number of drones, N	1,027	982	1,065
Mean weight, mg	200.13^a	190.67^b	198.14^a
SD	27.44	30.05	31.98
SE±	0.86	0.96	0.98
CV, %	13.71	15.76	16.14

Multiple range test (^{Duncan 1955})

Different letters indicate significant differences P ˂ 0.05

It is recognized that, as the size of the brood comb cell increases, an increase of the weight of the emerging drone is obtained under the given conditions. A positive correlation (P ˂ 0.10), but weak, was observed between the diameter of the brood cells and the weight of drones at birth (table 6), mainly attributed to the mentioned environmental effects. The greatest weight differences were observed between the SJ and T1 apiaries, but it was not possible to determine the number of cycles developed in the sampled combs. In Spain, ^{Arias et al. (2006)} reported a mean similar to November (200 mg), also in drones at birth. Meanwhile, ^{Bande et al. (2008)}, in Cuba, obtained a mean of 280.12 mg, but from already fed individuals. This result is superior to that indicated by ^{Ocaña-Nápoles (2014)}, also for flying drones (233 mg) in the area of San José de las Lajas.

Table 6 Relationship between cell diameter and drone weight 

Independent variable	Cell diameter
Dependent variable	Drone weight
ANOVA	P= 0.086 (˂ 0.10)
Coefficient of correlation	0.091
R^2	0.83%
SE±	21.60

Although in appearance, this result would be in contradiction with the previous ones, it should be considered that it includes all cells, where different effects overlap, and some are opposite. Since it is not possible to determine the internal diameters, larger cells may be older and, therefore, have their capacity decreased. In addition, the intensity of parasitization by Varroa also interacts and results in a distorting effect.

There does not seem to be a clear explanation for the differences in mean weight of drones between November and December-January (table 7).

Table 7 Mean weight of drones at birth per months 

Indicators	November	December	January
Number of drones	979	991	1 104
Mean weight, mg	203.56^a	191.57^b	194.44^c
SD	32.56	28.60	28.13
SE ±	1.04	0.91	0.85
CV, %	15.99	14.93	14.46

Multiple range test (^{Duncan 1955})

Different letters indicate significant differences P ˂ 0.05

It is probable that this difference expresses the result of interactions among several factors, such as the quantity and quality of food. In turn, they depend, for their production, on the reserves of bee bread, the entry of freshly harvested pollen and the availability of honey or nectar. At the same time, the production of these foods is conditioned by the numbers of foraging and nurse bees. As all these factors are highly variable and their status may reflect prior deficiencies or imbalances, it is extremely difficult to determine the causes in a short-term, specific study. To this should be added the fact that the production of drones does not follow the same patterns as that of workers and is more dependent on the abundance of food and the time of year (^{Verde et al. 2012}).

All drones examined at birth (3 071) were black. It is surprising that ^{Ocaña-Nápoles (2014)} has determined, in the same area, 60% intermediate color, 18% black and 22% yellow, but in individuals captured at random within the hive. In the absence of paternal inheritance in drones, the explanation should be in the change of queens, which is carried out at least once a year, although it is necessary to deepen the matter.

The extent of invasion in this brood was high, to the extent that its mean values ​​exceeded 70%, in SJ as in the hives of T1 and T2 (table 8). These values ​​are at the level of those determined in 1996-1997 by ^{Demedio (2001)} at the beginning of the epizooty of varroosis, in San José de las Lajas municipality. They are also consistent with reports by ^{Sanabria (2007)} and ^{Sanabria et al. (2015)}, also in the same area. Apparently, the situation is unusual because then, the first contact of the local bee with the parasite occurred. Meanwhile, by 2016, there was a history of coexistence. According to some criteria (^{Pérez-Morfi and Pérez-Piñeiro 2018}), the current bees are descendants of those that survived the initial impact of the mite, a result of natural selection, and the subsequent work of the selection and improvement program that continues today. Apparently, it is not appropriate to talk about natural selection in intensive beekeeping.

Table 8 Extent and invasion intensity per apiaries 

Indicators	SJ	T1	T2	Total
Examined cells	1,025	1,000	1,046	3,071
Parasitized cells	749	756	787	2,292
Mean E.I., % - Compaprop	73.07	75.60	75.24	74.63
Total mites	1,979	2,168	2,306	6,453
I.I. (Mean) - Duncan test	2.64^a	2.87^b	2.93^b	2.81

Comparison of proportions: F= 1.01 n.s.

Multiple range test (^{Duncan 1955}): P ˂ 0.05

Different letters indicate significant differences

The current high values could be explained by the scarcity of this type of breeding in the evaluated months, which, together with its greater and longer attractiveness for the founding females (^{Granadillo 2009}), results in a high percentage of parasitized cells. ^{Drijfhout et al. (2005)} observed that varroa mites show a preference for drone brood up to nine times greater, and that royal jelly exerts a deterrent effect on queen cells. Especially for CCR, these situations should call attention to the need to apply an organic treatment strategy that, due to its safety and efficacy (^{Reyes 2016}), allows these indexes to be reduced.

In the search for a possible effect of the parasite on the morphological parameters of drones at birth, invasion intensity is the quantitative indicator that allows determining a possible influence. However, the combination of both offers an evaluative criterion of the severity of the parasitic manifestation, as it is a cloistered host that is affected, at this stage, only by the founding females and their offspring.

As can be observed, invasion intensity was lower in the SJ apiary, although it should be considered that the mean difference does not exceed unity, that is, an individual. Something similar can be seen in the analysis per months (table 9). Despite a specific drop that is difficult to explain, in December (one sampling), November and January, the same values and mean invasion intensity are presented, although with statistical differences. Due to the effect, they should not significantly differ, as they do not even reach half a unit.

Table 9 Invasion extension (mean) and invasion intensity (mean) of V. destructor per months 

Indicators	November	December	January	Quarterly Totals
Examined cells	980	1 008	1 083	3 071
Parasitized cells	752	711	828	2 291
Mean E.I., %	76.73^a	70.53^b	76.45^a	74.60
Total mites	2 224	1 853	2 376	6 453
I.I. (Mean)	2.96^a	2.61^b	2.87^a	2.82

Comparison of proportions: F= 6.55**

Multiple range test (^{Duncan 1955}): P ˂ 0.05

Different letters in the same line indicate significant differences

By taking invasion intensity as an independent variable and the morphometric parameters of drones at hatching (body length and weight) as dependent variables, a weak or non-significant relationship was determined (tables 10 and 11).

Table 10 Correlation between invasion intensity and drone weight at hatching 

Independent variable	Invasion intensity
Dependent variable	Drone weight at hatching
ANOVA	P=0.48 (˃0.10) non-significant relationship among variables
Coefficient of correlation	0.013
R^2	0.016%
SE	30.17

Table 11 Correlation between invasion intensity and drone length 

Independent variable	Invasion intensity
Dependent variable	Drone length
ANOVA	P= 0.64 (˃ 0.10)
Coefficient of correlation	= 0.008
R^2	= 0.007 %
SE	= 0.069

It is evident that the relatively low general mean load of parasites per cell did not significantly influence mean weight and length of newborn individuals. However, ^{Getchev (1995)} observed a weight loss between 11 and 19% according to the infestation rate, which causes a decrease in their flight capacity. This situation depends on the number of mother mites, although ^{Rosenkranz et al. (2010)} stated that a single female of V. destructor can produce a mean loss of 7% of the bee weight. Although mites cause a significant reduction of weight and size of workers, a similar loss was not observed in the results with the drones of the current study. Likewise, it was manifested when comparing mean values ​​of this parameter (table 12) with the inclusion of all the parasitized cells.

Table 12 Comparison between mean weight of hatched drones from parasitized and non-parasitized cells 

Indicators	Parasitized cells	Non-parasitized cells
Mean weight, mg	204.00	200.00
SD	18.62	26.57
SE±	2.34	2.53

Comparison of means: N= 180; p = 0.41. (n.s.)

The result was different when comparing the weights of hatched individuals from cells with 5-6 mites, but not with 3-4 mites and those not parasitized (tables 13 and 14).

Table 13 Comparison between mean weight of cells parasitized with 3-4 mites and the non-parasitized ones 

Indicators	Parasitized cells (3-4 mites)	Non-parasitized cells
Mean weight, mg	199.75	200.00
SD	21.19	21.69
SE±	1.92	1.96

Comparison of means: N= 122; p= 0.54 n.s.

Table 14 Comparison between mean weight of drones parasitized with 5-6 mites and the non-parasitized ones 

Indicators	Parasitized cells (5-6 mites)	Non-parasitized cells
Mean weight, mg	188.04^a	200.00^b
SD	22.45	17.09
SE±	3.64	2.77

Comparison of means: N= 38; p= 0.005

It was confirmed that, to produce a significant effect of reduction in the morphometric parameters under the conditions of this study, there must be an invasion intensity superior to 4. However, it is likely that the concurrence of other factors of a nutritional or biological nature may promote measurable quantitative effects, with lower infestation rates.

An already known effect of reducing the weight of worker bees when they hatch is visible, which is the result, among other factors, of the spoilage action of adult females and juvenile stages of the mite. In this case, it is evident in drones, which breeding is more attractive and leads to greater reproductive success (^{Granadillo 2009}), in addition to a proven harmful action on the immune system (^{Ramsey 2018} and ^{Larsen et al. 2019}). This fact is of special interest in the paternal hives from the CCR, and this is because, besides drone breeding is favored, the application of varroicidal treatments is prohibited, even those accepted by the requirements of organic beekeeping (^{MINAG 2013}).

Morphological determinations indicate that they are drones of European lineage and a negative influence of parasitism by V. destructor mite was verified. High infestation rates were found in commercial hives, and most alarming, in paternal hives of a CCR. They were favored by their naturally abundant presence and the non-application of organic treatment, despite being accepted by the rigorous requirements established by the beekeeping production of this category.

The studied area lacks studies that are in correspondence with the value that must be restored to male bees. These results are just one step on the path to biometric characterization of drones and the factors that affect them. A larger-scale study is required, in which drones of the country are characterized, including physiological parameters such as sperm counts and their relationship with the quality of the queens produced in multiplying centers, without omitting their subsequent performance in the production hives.

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Received: December 22, 2020; Accepted: February 17, 2021

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Conflict of interest: The authors declare that there are no conflicts of interests among them

Author´s contribution: Leyanis Ocaña Nápoles: Experimental design, conducting the experiment, writing the manuscript.Anisley Pérez Hernández: Conducting the experiment, manuscript revision. Tamara Fernández Gómez: Data analysis, bibliography review. Jorge Demedio Lorenzo: Original idea, experimental design, writing the manuscript.