Entomological Science (2009) 12, 208–214 doi:10.1111/j.1479-8298.2009.00324.

ORIGINAL ARTICLE ens_324 208..214

Monthly changes in various drone characteristics of

Apis mellifera ligustica and Apis mellifera syriaca
Shahera ZAITOUN1, Abd AL-MAJEED AL-GHZAWI2 and Rami KRIDLI3
1
Department of Plant Production and Protection, Faculty of Agricultural Technology, Al-Balqa’ Applied University, Al-Salt,
2
Department of Plant Production, Faculty of Agriculture, Jordan University of Science and Technology, and 3Department of
Animal Production, Faculty of Agriculture, Jordan University of Science and Technology, Irbid, Jordan

Abstract
This study was conducted to investigate drone rearing activity and semen production of Apis mellifera
ligustica and Apis mellifera syriaca. Tendency of worker bees of both subspecies towards egg laying under
semiarid conditions were also monitored in the experiments. Differences were not observed in drone brood
production between both honeybee subspecies throughout the investigation. Worker bees of both subspecies
needed a significantly shorter time to start egg laying during February and March in comparison with the
time those workers needed for laying eggs during the remaining months of the study. Syrian bee workers
started egg laying earlier than Italian bee workers. Drones from laying workers were much smaller and
produced less sperms with more abnormalities than normal drones. Drones produced from queens in May
were heavier and produced more sperms with less abnormalities than those produced during the other
months. The drone brood rearing of both subspecies tended to follow the same general cycle in 2005 and
2006. The study suggests that virgin queens have a better chance to receive adequate viable sperm amounts
from drones in April and May in semiarid Mediterranean conditions.
Key words: drone rearing, honeybee species, laying workers, semen quality.

INTRODUCTION negative feedback mechanism, through which males’

presence limits further drone production in colonies
Queen rearing is an essential step improving beekeep- (Free & Williams 1975; Rinderer et al. 1985; Omholt
ing and bee stocks. Beekeepers often re-queen in colo- 1988; Henderson 1991; Henderson 1994).
nies that contain bees that are susceptible to diseases or Food resource abundance, swarm behavior and
have strong defensive behavior. Periodical re-queening worker population per colony are among the other
with young queens, less than 1 year old, results in more factors involved in drone production (Crane 1990;
honey production than the amounts produced by colo- McNally & Schneider 1994; Tiesler & Englert 1997).
nies headed by old queens (Kostarelou-Damianidou Drone rearing activities in colonies start with the
et al. 1995). Production of viable drones is a limiting increased nectar flow and pollen yield. Peak drone pro-
factor in successful queen rearing activities. Worker duction coincides with the peak of resources availability
bees regulate the number of drones in colonies by lim- (McNally & Schneider 1994). Most drones are reared
iting the amount of drone combs constructed and the during the reproductive phase of the colony (swarm
production of drone broods, and by evicting adult preparation) (Crane 1990) and the drone production is
drones from the colony (Ribbands 1953; Ruttner influenced by some of the same factors that affect
1956). Furthermore, previous studies suggested a swarming activities (Allen 1958; Winston 1987). Drone
production was found to increase by increasing foraging
activity because ample food resources are necessary to
Correspondance: Shahera Zaitoun, Department of Plant
Production and Protection, Faculty of Agricultural stimulate colony growth that precedes swarming
Technology, Al-Balqa’ Applied University, Al-Salt, Jordan. (Fletcher 1978; Seeley 1985; Winston 1987). Further-
Email: zaitoun@bau.edu.jo more, large colonies were observed to rear more drones
Received 7 April 2008; accepted 7 January 2009. because sufficient resources are available for rearing and

© 2009 The Entomological Society of Japan

 Factors affecting drone quality

maintaining drones of these colonies (Winston 1987). this study. For each subspecies, 28 colonies, each estab-
When the next dearth season approaches, workers drive lished in ten-framed Langstroth hives, were used. In
the drones out of the colony where they die (Dathe November of each experimental year, colonies were
1975; Crane 1990). located in the Jordan Valley and were kept there until
During spring and early summer months, colonies the early part of April, that coincided with the end of the
produce large numbers of drones. Queens of Apis mel- blooming season for citrus trees. Thereafter, honeybee
lifera lay unfertilized eggs in larger cells for drones as a hives were transported again to the university campus
normal method for drone production in the colonies and were kept there for the remaining months (April to
(Koeniger 1970). In certain cases, a few unfertilized eggs October). The paternal Italian colonies were headed by
are commonly found in the worker cells as a result of standard marked queens imported from the USA, while
depletion of the queens’ sperm storage or for other Syrian colonies were headed by queens of syrian bees
reasons. Drones from worker cells are significantly produced locally in an A. mellifera isolated area using
smaller than drones from drone cells (Berg 1991; Berg standard methods described by Laidlaw (1979). The
et al. 1997). The smaller drones have lower reproductive same procedures were performed during the second year
success compaired to normal drones (Berg et al. 1997). of the study. During the investigation, colonies were
Drones of worker cells may be laid by laying workers subjected to different apiculture practices such as
(Currie 1987). shading, feeding, supering, swarm control and Varroa-
Under semiarid conditions, both Syrian bees Apis mel- control, as needed, in both experimental sites.
lifera syriaca, a native subspecies, and Apis mellifera
ligustica, a main race, are kept in Jordan. Both drone Drone rearing and viability
rearing activity and drone reproductive characteristics Drones of both subspecies were produced following two
are not investigated under semiarid conditions. Most procedures. In the first one, drones were produced by
beekeepers in Jordan tend to rear queens during the placing a drone comb in a hive for a period that
summer months to prevent jeopardizing honey produc- extended from January to July of each year (n = 14
tion during the spring. This study was conducted to colonies). In the second case, however, the mother queen
evaluate monthly changes in drone production, and to was removed from the colony and emerging queens were
compare semen production of A. m. ligustica and A. m. destroyed to develop laying workers and to produce
syriaca. Also the study aimed to monitor the tendency of drones from these laying workers (n = 14 colonies). All
worker bees of both subspecies towards egg laying experimental colonies were fed with protein cake
under semiarid conditions. imported from Germany (Nektapol). To quantify the
population dynamics of the drones, the number of drone
brood cells occupied was counted at 24 day intervals
MATERIALS AND METHODS throughout the experimental period according to the
method described by Gerig (1983). After maturation, 50
Study sites
drones were caught (using drone traps fitted at the hive
Experiments were conducted at Jordan University of enterance) monthly and weighed on an electric balance
Science and Technology Campus (JUST), Irbid (⫾0.1 mg). Sperms were collected from the vesiculae
(32°30′N, 35°59′E; 600 m a.s.l.) and at North Shuna seminales (Koeniger et al. 1994) of these drones. Sper-
(32°37′N, 35°36′E; 200 m a.s.l.), Jordan Valley, during matozoa were counted in hemocytometer counting
2005 and 2006. The first area is characterized by a hot, chambers. Sperm viability and abnormality percentages
dry summer and cold, semi-dry winters, while the were determined according to the method described by
second location is characterized by very hot dry Lodesani et al. (2004). Drone fertility was evaluated by
summers and mild winters. In the Jordan Valley, the applying pressure on the abdominal cavity to exteriorize
main nectar flow occurs from January to March, mostly the male organs. The presence of a creamy fluid drop at
originating from citrus and Sinapis spp., while the main the tip of the male organ indicated that the male was
nectar flow in Irbid area occurs from April to July origi- fertile, while a clear fluid drop indicated that the male
nating from fruit trees and native wild flowers, mostly was infertile.
from Sinapis spp., Centaurea spp., Balluta undulata.
Statistical analysis
Bee colonies Least-square anova was used to study the effect of
Two honey bee subspecies, A. m. ligustica Spinola, 1806 subspecies with month as a repeated measure of
(very common honeybee subspecies) and A. m. syriaca semen characteristics. Drone production and semen
Buttel-Reepen, 1906 (a native subspecies) were used in characteristics were submitted to a repeated measures

Entomological Science (2009) 12, 208–214 209

© 2009 The Entomological Society of Japan
S. Zaitoun et al.

Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006

Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006

20
6000
18
No. of brood cells

5000 16
4000 14
12

Days
3000
10
2000
8
1000 6
0 4
February March April May June July August 2
0
Figure 1 Monthly changes in the number of drone cells occu- February March April May June July
pied as influenced by subspecies and year (mean ⫾ standard
error). Figure 2 Monthly changes in days for worker bees to start egg
laying as influenced by subspecies and year (mean ⫾ standard
error).

multivariate model by the “repeated” statement, to

evaluate the effect of the within-subject “sampling
month” factor, and the between-subject “subspecies”
Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006
factor (SAS 1997). Each year was analyzed
225
independently. A

200

RESULTS 175

The rearing activities of drone brood in both subspecies 150

(Fig. 1) started in February as the first nectar flow and B
Drone weight (mg)

pollen yield appeared, usually from wild plants and 125

250
vegetables. Drone brood production continued as pollen
yield and nectar flow successioned through February. 225

The highest brood population for the entire season was 200
recorded in April with 5300 and 4500 brood cells for A.
175
m. ligustica and A. m. syriaca, respectively. This coin-
cided with the the main honey flow of citrus trees. There 150

were no significant differences (P > 0.05) in drone brood 125

production between either honeybee subspecies February March April May June July August

throughout the study. Brood rearing decreased gradually

Figure 3 Monthly changes in the weight of drones from
thereafter, reaching a brood stop during August in both workers (A) and queens (B) as influenced by subspecies and
subspecies. year (mean ⫾ standard error).
Figure 2 shows the time needed in queenless colonies
for worker bees to start egg laying during the study
period. The tendency of being a laying worker was
greatly affected by bee subspecies and season of rearing. were much smaller than normal drones. Average drone
Worker bees of both subspecies needed a significantly weight from worker Italian bees (181 mg) was not sig-
shorter time to start egg laying during February and nificantly heavier than that from Syrian workers
March compared to the time needed during the remain- (170 mg) as shown in Figure 3(A).
ing months. Syrian bee workers started egg laying only Normal drones produced from queens in May were
3 days after queen removal during February and March, heavier (232 mg and 197 mg A. m. ligustica and A. m.
while Italian bee workers started egg laying after 8 days syriaca, respectively ) than those produced during other
during the same period. In May, the time needed for months (Fig. 3B). The average weight of drones pro-
worker bees to start egg laying was 12 and 18 days for duced by queens was significantly greater in A. m. ligus-
A. m. ligustica and A. m. syriaca, respectively. tica (203 mg) than in A. m. syriaca (181 mg) subspecies.
The time of rearing drone brood affected the drone Figure 4(A) shows that drones originating from
weight in both subspecies. Drones from laying workers worker bees were less fertile than normal drones and

210 Entomological Science (2009) 12, 208–214

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 Factors affecting drone quality

Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006 Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006

A 10
80 A
9
70
8
60 7
50 6

Sperm number (millions)

40 5
Drone fertility (%)

30 B 4
20 3
B
90
13
80 12
70 11
60 10
50 9
40 8
30 7
20 6
March April May June July August 5
February March April May June July August
Figure 4 Monthly changes in fertility of drones from workers
(A) and queens (B) as influenced by subspecies and year Figure 5 Monthly changes in sperm numbers of drones from
(mean ⫾ standard error). workers (A) and queens (B) as influenced by subspecies and
year (mean ⫾ standard error).

produced an average of 47% (range, 35–66%) and Syriaca 2005 Syriaca 2006 Ligustica 2005 Ligustica 2006

46.9% (range, 32–70%) of the normal drone sperm 60

A
production for A. m. ligustica and A. m. syriaca, 50
respectively. The highest percentage of drone fertility 40
of queen-produced drones was recorded in May for 30

both A. m. ligustica 81% (range, 40–81%) and A. m. 20

Sperm abnormality (%)

syriaca 71% (range, 33–71%) as shown in 10

Figure 4(B). 0
50
B
Drones from A. m. ligustica workers produced an 40
average of 6.8 million sperms (range, 5.4–8.5 million)
30
compared with 6.1 million sperms for drones from A.
20
m. syriaca workers (range, 4.3–7.8 million) as shown
in Figure 5(A). The average sperm numbers of normal 10

A. m. ligustica drones was 10.2 million (range, 0

February March April May June July August
8–12.8 million) compared with 8.8 million for A. m.
syriaca drones (range, 8.8–10.6 million) as shown in Figure 6 Monthly changes in sperm abnormality of drones
Figure 5(B). from workers (A) and queens (B) as influenced by subspecies
Sperm abnormalities were recorded in drones from and year (mean ⫾ standard error).
laying workers as well as normal drones. There were no
significant differences in sperm abnormality percentage
in drones of either origin. Drones from laying workers
DISCUSSION
of both subspecies showed higher sperm abnormalities.
Twenty-six percent (range, 13.6–50.2%) and 24% Results of this study revealed three main observations
(range, 11.2–48.2%) of Italian and Syrian sperms origi- about drone production of bee colonies maintained
nating from laying workers drones were abnormal, under semiarid conditions. The first observation was
respectively, as shown in Figure 6(A). On average, 21% that drone production under normal condition, by
(range, 8.8–39%) and 20% (range, 8.4–34.2%) of Italian and Syrian bees occurred primarily during a
sperm output of queen-produced drones of A. m. ligus- relatively long period extending from February to July.
tica and A. m. syriaca, respectively, were abnormal as The activities of drone brood rearing during this
shown in Figure 6(B). period can be attributed to the presence of adequate

Entomological Science (2009) 12, 208–214 211

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S. Zaitoun et al.

number of nurse bees, and the availability of nectar sperms) than Apis koschevnikovi (101 mg, 0.13 million)
and pollen from wild plants and fruit trees in the area. and Apis andreniformis (71 mg, 1.7 million) (Koeniger
Furtheremore, the peak of drone production was et al. 1994). Apis cerana drones are larger (83.4 mg)
during April and May, which coincided with the than A. koschevnikovi drones and they produce a
swarming season and the highest brood and worker greater number of spermatozoa (1 million) (Ruttner
population (Zaitoun 2000) and with the time at which 1988; Ruttner & Maul 1969, 1983). These results agree
most new queens are reared (Al-ghzawi & Zaitoun with the general rule that larger drones have more sper-
2008). Drone brood rearing activities decreased from matozoa (Koeniger et al. 1994). The results prove the
April until the last sampling date in August due to a occurrence of abnormal sperms in high rates in drones
comparative lack of incoming nectar and pollen in this of both subspecies and in higher rates in drones origi-
period. Similar results of drone production in a certain nating from laying workers. These drones with high
limitted period was reported in several studies sperm abnormalities, especially those reared in late
(Winston 1987; McNally & Schneider 1992, 1994; summer, may fly and mate with virgin queens. Such
Schneider & McNally 1994). drones may be responsible for unsatisfactory queens
Less time was needed by workers to start egg laying produced in summer. These results are in agreement
in February and March than during other periods of with Lodesani et al. (2004) who reported the presence of
the study. In the same context, the local bees needed frequent anomalies in sperms in drones in addition to
less time to start egg laying than Italian bees. Accord- the significant variability among drones of the same
ing to Wossler (2002), several factors can influence the colony.
workers’ tendency to lay eggs. These include phero- The third viewpoint was that the number of drones
monal factors, environmental factors, physiological originated from laying workers was not significantly
factors (e.g. age and ovariole number) and genetic vari- affected by the subspecies nor by the time of rearing.
ability. One or more of these factors may have influ- Furthermore, all reproductive characteristics measured
enced worker laying in the current study. The presence – drone viability, sperm number and sperm viability/
of a large amount of brood may have inhibited ovarian drone – were lower in drones originated from workers
development in workers due to the presence of brood than in those from queens. Berg (1992) reported that
pheromones (Jay 1970; Wossler 2002). Nutritional A. mellifera drones originating from worker cells were
abundance may affect laying workers in spring and smaller in size than normal drones but they had a
early summer months as observed by delaying ovarian similar amount of spermatozoa. This disagreement
development, thus egg laying (Wheeler 1996). This with our results may be related to the influence of
nutritional effect was observed as more time was environmental factors on physiological aspects of
needed by workers to lay eggs during the spring and sperm production.
early summer when nutrients were more abundant. The production of drones was possible for a period
Additionally, the age of workers may affect reproduc- extending from February to July. Drone production
tion (Delaplane & Harbo 1987; Hepburn et al. 1991). during the non-breeding season was possible for the
In the current study, the presence of old winter bees same period through laying workers. The best drone
during winter and early spring months may have pro- characteristics were achieved during May. There were
moted the tendency to start egg laying (hastened the great variations in qualitative and quantitative charac-
process). Crane (1990) reported a longer duration to teristics of drones originating from queens or workers
the start of egg laying in European than in tropical during non-breeding season. It is very important for
bees. Additionally, she reported differences in duration beekeepers to synchronize queen rearing with the avail-
to egg laying within the same race reared under differ- ability of high viable drone production between April
ent environmental conditions. and June under semiarid conditions.
The second observation suggests that adult drone
quality was strongly influenced by the time of drone
rearing. Each subspecies has its own physiological and
ACKNOWLEDGMENTS
reproductive characteristics (Ruttner 1988). The drones
of A. m. ligustica showed higher weights, viability and We acknowledge the Higher Council for Science and
total sperm number per drone compared to A. m. Technology, Agriculture sector, Amman, Jordan, for the
syriaca. Drone weight and the number of spermatozoa financial support. Our sincere appreciation goes to
they produced seem to be species-specific (Koeniger Al-Balqa Applied University, As-Salt and to Jordan Uni-
et al. 1996). A. mellifera drones were larger and the versity of Science and Technology, Irbid, Jordan, for
number of sperms were higher (220 mg, 10 million providing the laboratory facilities.

212 Entomological Science (2009) 12, 208–214

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 Factors affecting drone quality

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