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Natural patterns of caste and sex allocation in the stingless bees Melipona favosa and M. trinitatis related to worker behaviour

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This paper is the report of a long-duration study of the production of gynes and males in Melipona stingless bees in Trinidad and Tobago, including a behavioural study of laying workers. In 167 brood samples (16342 pupae) of M. favosa, taken from 78 colonies in the natural environment over the years 1993-2001, workers represented 78.4% and males represented 17.3%. Gynes represented 5.1% of all female brood. Gyne proportion never exceeded 22.5%. Gynes were found to be common throughout the year. Like the gynes, males were present all year, but their occurrence varied over the months. Males were most common in the months of July and August. At the colony level male occurrence in the brood was characterized by very high values (maximum 74.2%), next to a frequent complete absence (in 26.5% of all samples). The finding of bout-like production of males at the colony level is supported by the observations on reproductive worker behaviour. The colonies appeared to be in different phases of male production. When male producing laying workers were present, they competed heavily for egg-laying opportunities. Various behaviours of laying workers and the queen are described and interpreted on the basis of reproductive competition and kin conflict theories. From these results, we conclude that in M. favosa, workers have a distinct influence on reproduction, including the production of gynes and males.
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Summary. This paper is the report of a long-duration study
of the production of gynes and males in Melipona stingless
bees in Trinidad and Tobago, including a behavioural study of
laying workers. In 167 brood samples (16342 pupae) of M.
favosa, taken from 78 colonies in the natural environment
over the years 19932001, workers represented 78.4% and
males represented 17.3%. Gynes represented 5.1% of all fe-
male brood. Gyne proportion never exceeded 22.5%. Gynes
were found to be common throughout the year. Like the gy-
nes, males were present all year, but their occurrence varied
over the months. Males were most common in the months of
July and August. At the colony level male occurrence in the
brood was characterized by very high values (maximum
74.2%), next to a frequent complete absence (in 26.5% of all
samples). The finding of bout-like production of males at the
colony level is supported by the observations on reproductive
worker behaviour. The colonies appeared to be in different
phases of male production. When male producing laying
workers were present, they competed heavily for egg-laying
opportunities. Various behaviours of laying workers and the
queen are described and interpreted on the basis of repro-
ductive competition and kin conflict theories. From these re-
sults, we conclude that in M. favosa, workers have a distinct
influence on reproduction, including the production of gynes
and males.
Key words: Male production, gyne production, worker be-
haviour, stingless bees.
Introduction
In eusocial Hymenoptera the mated female has the possibil-
ity to decide whether she will lay fertilised or unfertilised
eggs, resulting in female and male brood respectively. In some
taxa unmated workers may participate in the production of
males (Crozier and Pamilo, 1996; Bourke and Franks, 1995;
Bourke and Ratnieks, 1999). In species where colonies are
founded by single females, usually many sexuals are pro-
duced. If colony multiplication takes place by ‘swarming’,
sexual females are usually produced in small numbers and
only when needed. Males are seasonally numerous when
swarming is seasonal. When swarming can take place over the
entire year, one would expect males and sexual females at the
population level to be present all year. However, Melipona
stingless bees have a very low incidence of ‘swarming’.
Colonies of these species have a low mortality and laying
queens have a high longevity. This raises questions concern-
ing the production of sexuals in this group.
Diploid brood in eusocial Apidae can develop into two
different castes: workers or queens. In most eusocial bees,
queens emerge from ‘queen cells’ that are distinctly larger
than cells from which workers emerge. In these species, queen
determination is trophically regulated through larval food
(Michener, 1976). Melipona bees are unique for the rearing
of all castes and sexes from a single-sized brood cell. In
Melipona, queens are produced continuously and in high
numbers (Sakagami, 1982). In this genus queen determina-
tion has been proposed to have a genetic component in addi-
tion to being influenced by trophic factors (Kerr et al., 1962;
Velthuis and Sommeijer, 1990; 1991). Recently, the high pro-
duction of queens in Melipona has been explained through the
occurrence of a caste conflict (Ratnieks, 2001). The haplo-
diploid system determines different degrees of relatedness of
female bees with their own offspring as compared to that with
their sisters. The proposed caste conflict hypothesis implies
that female Melipona larvae, through self-determination, tend
to develop into queens whereas workers tend to produce sis-
ter workers.
This article contains the results of our long-term study on
caste and sex allocation in M. favosa. Focussing on the spe-
cial role of workers in the production of the different types of
Insectes Soc. 50 (2003) 38–44
0020-1812/03/010038-07
© Birkhäuser Verlag, Basel, 2003
Insectes Sociaux
Research article
Natural patterns of caste and sex allocation in the stingless bees
Melipona favosa and M. trinitatis related to worker behaviour
M.J. Sommeijer1,L.L.M.de Bruijn1,F.J.A.J.Meeuwsen1and E.P. Martens2
1Utrecht University, Social Insects Department, P.O. Box 80.086, NL-3508 TB Utrecht, The Netherlands, e-mail: m.j.sommeijer@bio.uu.nl
2Utrecht University, Centre of Biostatistics, Padualaan 14, NL-3584 CH Utrecht, The Netherlands, e-mail: e.p.martens@bio.uu.nl
Received 12 September 2001; revised 15 July 2002; accepted 21 August 2002.
Insectes Soc. Vol. 50, 2003 Research article 39
months. However, the relative occurrence of gynes at the pop-
ulation level did not vary significantly in relation to the time
of the year (Kruskal-Wallis, p = 0.599).
The occurrence of males in M. favosa
Males were also found during all months of the year. The
monthly occurrence of males at the population level is given
in Figure 3. In contrast with the occurence of gynes their
numbers differed significantly over months (Kruskal-Wallis,
P<0.001), reaching peak values in the months of July and
August (25.9% and 29.7% respectively). Minimum values
were found in samples of May and in the (small number) of
individuals in the colony, we will also describe in detail the
behaviour and particularly the social interactions of drone-
producing workers. The occurrence of such worker behaviour
in a series of colonies under simultaneous observation will
be analysed. The theoretical impact of the results will
be discussed at the colony level as well as at the population
level.
Materials and methods
In the period of 1993–2001, we analysed 176 brood samples (contain-
ing a total number of 16342 brood cells) from 78 different colonies of
M. favosa in Trinidad and Tobago, W.I. These colonies were located at
different sites in their natural habitat. Multiple samples of the same
colonies were not taken within 6 months of each other to ensure inde-
pendance of the samples. The samples were taken throughout the year
from brood containing pupae of an age at which they have at least
coloured eyes. Whenever possible, we extracted entire combs as a sam-
ple. Some samples were immediately analysed for sex and caste, others
were preserved in alcohol and analysed at a later moment. For the analy-
ses we discarded the samples which consisted of less than 40 cells.
Of M. trinitatis, 21 samples were analysed, taken in four different
months from 15 colonies at two different locations.
Oviposition behaviour was studied during three observations periods
of 29, 14 and 15 hours respectively, all within one month in 1998. In this
way, we simultaneously recorded the behaviour of workers during ovipo-
sition in ten colonies of M. favosa, some of which were producing males.
The colonies had populations of 100 to 400 bees, which is normal for
thriving colonies of this species. They were housed in hives with a glass
lid and installed in their natural habitat where they could forage nor-
mally. Through the non-stop intensive recordings by four experienced
observers it was possible to observe all ‘Provisioning and Oviposition
Processes, POP’s’ (Sakagami, 1982) during those days. Special attention
was paid to the behaviour and social interactions of the workers and the
queen during each POP.
Results
The occurrence of castes and sexes
Of the total number of pupae of M. favosa workers repre-
sented 78.4% and males represented 17.3%. Gynes repre-
sented 5.1% of all female brood. For the smaller data set on
M. trinitatis (2567 pupae), these figures were 87.6%, 7.7%
and 4.8% respectively.
The occurrence of gynes in M. favosa
At the level of the samples, there was variation in the per-
centage of gynes, and in most of the samples gynes were pre-
sent. In Figure 1a frequency distribution is plotted for the
gyne-proportion of females. Although we found 14% of the
samples to contain no gynes at all, at the population level gy-
nes were found to occur throughout the year. The proportion
gynes-of-females ranged from 0 to 22.5% (average: 5.0%; sd:
4.4%). The monthly occurrence of gynes, as a percentage of
all females is given in Figure 2. We have no samples for the
months of April and June, whereas the numbers of samples
for March and October are small compared to those in other
Figure 1. Frequency distribution of the proportion of gynes-of-females
in brood samples of Melipona favosa (n = 176 samples) and Melipona
trinitatis (n = 21 samples)
40 M.J. Sommeijer et al. Caste and sex allocation and worker behaviour in Melipona
Tab le 1. POP-rates per colony during three observation series
Colony: T1 T2 T7 B1 B2 W2 B3 B5 W6 W8 all colls.
# POP’s 25–27 Jul (29 hrs) 22 31 22 4 19 6 104
pop/hr 0.76 1.07 0.76 0.14 0.66 0.21 0.6
# POP’s 6 Aug (14 hrs) 6 10 12 12 7 9 9 19 13 97
pop/hr 0.43 0.71 0.86 0.86 0.5 0.64 0.64 1.36 0.93 0.77
# POP’s 14 Aug (15 hrs) 19 1 17 16 17 13 14 18 11 126
pop/hr 1.27 0.07 1.13 1.07 1.13 0.87 0.93 1.2 0.73 0.93
total # POP’s 47 42 51 32 43 6 22 23 37 24 327
average POP-rate 0.81 0.72 0.88 0.55 0.74 0.21 0.76 0.79 1.28 0.83 0.75
Figure 2. Monthly occurrence of gynes at the population level Figure 3. Monthly occurrence of males at the population level
1We tested whether mutiple samples over the period of eight years taken
from some of the colonies were indeed independant by randomly
selecting only one sample per colony. Differences in male occurrence
between months remained significant.
Occurrence of ovipositions in M. favosa
Oviposition rates
During the three intranidal observation periods in 10 different
colonies a total number of 327 POP’s was observed. The
results are presented in Table 1. The oviposition rate for all
colonies during the total observation time of 58 hours aver-
aged at 0.8 POP’s/colony/hour. Individual colonies had dif-
ferent POP-rates for the total observation time, ranging from
0.2 1.3 POP’s/hour. The table indicates how POP rate can
also fluctuate within colonies.
The frequency of different POP-types
Oviposition behaviour occurred in different forms. We dis-
criminate between two major forms: Queen-POP’s and
Worker-POP’s (17.1% of all POP’s). In Queen-POP’s, the egg
that is finally operculated is laid by the queen, and in Worker-
POP’s this egg is laid by a worker. Worker-POP’s are charac-
samples of October (3.1% and 2.3% respectively).1At the
colony level, males occured in 73.5% of the samples and their
occurrence in the brood is characterized by very high values
(maximum 74.2%), next to a frequent complete absence.
The occurrence of sexuals in M. trinitatis
In M. trinitatis gynes and males were found to occur in sim-
ilar patterns as in M. favosa. Gynes were found to occur in
80.0% of all samples (n= 20), and gyne percentages in our
samples never exceeded 15.9% of all females (Fig. 1b).
Males however were often absent. They only occurred in
45.0% of the samples. When males were present, their per-
centage could reach high values (up to 30.7% of the pupae in
the sample).
Insectes Soc. Vol. 50, 2003 Research article 41
Behaviour of workers and the queen during POP’s in
colonies with RLW’s
The behaviour of queen and workers during a POP is very dif-
ferent between colonies where Worker-POP’s occur and
colonies that only have Queen-POP’s. The start of Worker-
POP’s is lengthy when the queen is not present at the very be-
ginning.
Description of worker behaviour during Worker-POP’s
At the start of a Worker-POP generally more workers are pre-
sent at that cell than in POP’s in colonies that are not in RLW-
phase (about 6 versus 2 workers). Workers in RLW-phase do
not perform the typical retreats from the queen (c.f. Som-
meijer and de Bruijn, 1984). In Worker-POP’s the food re-
gurgitations are usually temporally interrupted after the first
two or three discharges have taken place. During these inter-
ruptions workers may take up some of the larval food. The
competition between workers in these POP’s is clearly visible.
Workers try to push each other away from the cell and they
antennate each other very intensively. Worker interference in-
creases toward the end of a Worker-POP.
In this study we confirmed the earlier described behav-
ioural features of RLW’s. Particularly obvious in these obser-
vations was the strong drive of RLW’s to remain sitting on the
cell in which they had oviposited, in order to proceed imme-
diately with the operculation of the cell. This is in very sharp
contrast to the behaviour of laying workers that release trophic
worker eggs. Such workers immediately depart from the cell
after egg laying. The occurrence of various laying workers in
a single Worker-POP is always characterised by aggressive
mutual interactions. For example, a worker that assumes the
laying position may be interfered by another worker that fi-
nally obtains a position underneath the first worker, from
which position she can take over egg-laying. Workers may
also eat worker eggs and replace it by their own egg (in 7%
of the Worker-POP’s).
Description of queen behaviour during Worker-POP’s
The locomotive pattern of the queen in colonies with Worker-
POP’s is different from that in other colonies. In about ten
percent of the cases the queen was not even present during
the start of a Worker-POP. In fifty percent of the Worker-
POP’s the queen departed from the cell after the first food
discharges. These departures did not appear to be the result
of pushing or other interference by workers. In colonies
with Worker-POP’s we also observed the queen frequently
move to very distant parts of the nest, where she is not en-
countered in other colonies. During Worker-POP’s the queen
does not as heavily antennate and drum on discharging work-
ers with her front legs as is the case in colonies outside the
RLW-phase.
terized by the immediate operculation of the cell by the lay-
ing worker (a so-called ‘reproductive laying worker’RLW). In
each of these major types variation consists of whether or not
a trophic worker egg is released preceeding the laying of the
egg that is finally operculated. The frequencies of all four
POP-forms are listed in Table 2. Of all queen ovipositions,
28.8% was preceeded by the release of one or more trophic
worker eggs. For all reproductive worker eggs this was the
case in only 7.1%. In 327 observed POP’s we never recorded
a POP in which a worker egg was released after a queen’s
oviposition.
Comparing the oviposition rate of colonies in RLW-phase
with this in colonies without Worker-POP’s (Fig. 4), it can be
seen that the POP-rates in general are higher during RLW-
phase than out of RLW-phase. With the small sample sizes it
can not be shown that this difference is significant (Mann-
Whitney test: p= 0,079).
Tab le 2. The frequencies of the two major POP-forms (with a Queen
Egg, QE, or with a Reproductive Worker Egg, RWE) and of their sub-
forms (preceeded or not by a Trophic Worker Egg, TWE)
Frequency (%) % of total POP’s
TWE(s) + QE 78 (28.8) 23.9
QE 193 (71.2) 59
Total Queen-POP 271 82.9
TWE(s) + RWE 4 (7.1) 1.2
RWE 52 (92.9) 15.9
Total Worker-POP 56 17.1
Total POP’s 327 (100%)
Figure 4. Boxplots of oviposition rates during and out of Reproductive
Laying Worker (RLW)-phase
42 M.J. Sommeijer et al. Caste and sex allocation and worker behaviour in Melipona
Description of behaviour in Queen-POP’s in colonies in
RLW-phase
Queen-POP’s in colonies in RLW-phase are different from
POP’s that take place in colonies where RLW’s are absent (c.f.
Sommeijer and de Bruijn, 1984). They are more time-con-
suming through the little active behaviour of the queen and
through her frequent departures from the cell. In twenty per-
cent of these Queen-POP’s we observed the uptake of larval
food by the workers during provisioning. The eating of worker
eggs by sister workers prior to the final oviposition by the
queen occurred in two cases. These slowed-down POP’s could
lead to oviposition of four trophic eggs per POP. On the other
hand the reluctance of the queen to eat the trophic eggs even
resulted once in the presence of two worker eggs in the same
cell.
Discussion
Occurrence of gynes
A continuous queen production in Melipona colonies has ear-
lier been established (Kerr, 1950; Kerr et al., 1962; Ratnieks,
2001; Van Veen et al., 2000). Our present results again con-
firm that gynes are always present in colonies. In these sam-
ples we never obtained gyne-of-females percentages sur-
passing 22.5% for M. favosa and 15.9% for M. trinitatis. The
hypothesis that queen determination in Melipona is regulated
through the combination of genetic and nutritional determi-
nation factors (Kerr et al., 1962; Velthuis and Sommeijer,
1991; Sommeijer and De Bruijn, 1994) predicts maximum
gyne proportions of 25%. According to the recently proposed
caste conflict model by Ratnieks and Wenseleers (Ratnieks,
2001; Wenseleers et al., 2001), the optimum proportion of fe-
males that should develop into queens ranges from 14 to 20
percent. Our results provide support to both hypotheses. Con-
siderable variation in gyne proportion occurs in our samples
and such a large series of samples appears necessary to ac-
curately estimate the proportion of gynes. Spatial clustering
of gyne pupae in the combs, as reported by Koedam (1999),
should have lead to an occasional occurrence of a gyne per-
centage over 25% in at least some of our small samples.
Variation of gyne proportion in brood samples is not re-
flected at the population level. At this level gynes are present
in the same proportion throughout the year.
Male presence at the colony and the population level
Male proportion in the samples varies strongly. High per-
centages, next to complete absence of emerging males have
earlier been found in M. favosa by Chinh and co-workers
(Chinh et al., in press). These authors also established that the
typical pattern of rhythmic production of males in individual
colonies of M. favosa is the result of rhythmically occurring
reproductive laying worker behaviour in these colonies. It was
found that through this process a colony does not produce
males for periods of more than several months despite ongo-
ing brood cell production.
Within the population males are present throughout the
year, but distinct differences in male percentages are found
between months. A seasonal production of sexuals as a direct
result of changing environmental factors is not to be expected
in view of the fact that the development of young bees is a
slow process in this group of bees. This does not allow for a
fast reaction to these changes. However, the fluctuation in the
number of males over the year can possibly be explained by
the seasonally varying food stores of the colonies, as this has
been indicated to correlate with male production (Moo-Valle
et al., 2001).
Production of males by reproductive laying workers
In this study we confirmed the earlier finding (Som-
meijer et al., 1999) that reproductively laying workers are
common in M. favosa. It was also confirmed that the colonies
in a population may occur in different phases of RLW activ-
ity: some colonies may be male producing while other
colonies are not in this phase. Chinh and co-workers (in press)
demonstrated how in M. favosa RLW behaviour (in the
Reproductive Laying Worker Period, RLWP) is followed by
the Male Emergence Period, MEP. An ultimate function of
colonies occurring in different male producing phases may be
that this asynchrony prevents inbreeding. This mechanism
further garantees a continuous presence of males in the
population.
The different forms of worker oviposition
The behavioural elements during the different types of POP’s
appear to be similar to the descriptions of POP’s we earlier
published (Sommeijer and Van Buren, 1992). In the present
study we did not find the release of reproductive worker eggs
after the queen’s oviposition. Such a method for male pro-
duction, described to be normal in Scaptotrigona postica
(Bego, 1990; Beig, 1972) is certainly not a regular way for
male production in M. favosa. The release of reproductive
worker eggs after queen oviposition was only rarely seen by
us in a colony where the queen was to be replaced (Chinh
et al., in press).
Queen-worker relations and proximate mechanisms for the
occurrence of male producing workers
In many aspects Worker-POP’s in these queenright colonies
resemble POP’s in experimentally dequeened colonies, in
which there is also much aggression between workers (Som-
meijer and Velthuis, 1977). Overt mutual worker aggression
also occurs in colonies where the queen is recently accepted
and just starts to oviposit. In these colonies POP’s are also
characterised by a lengthy duration and by the queen leaving
the cell frequently during POP (De Bruijn pers. obs.). It ap-
Insectes Soc. Vol. 50, 2003 Research article 43
the presently studied Worker-POP’s, should also be inter-
preted to have a function in the reproductive competition
among workers.
Worker control over reproduction
In addition to their role in the production of males through the
laying of reproductive worker eggs, workers also may influ-
ence queen production. Their behaviour during POP serves to
regulate the quantity and quality of larval food in cells. Work-
ers also play a key role in worker production by regulating cell
construction. Typically in stingless bees, construction of a
brood cell is linked to the subsequent POP in that cell (Saka-
gami, 1982). The most important constructors of a brood cell
are, immediately after this, the provisioners of the same cell
(Sommeijer et al. 1982). Further, some of the building work-
ers initiate POP’s by urging the queen to visit the cell that is
ready to be oviposited (Sommeijer and de Bruijn, 1985). Dif-
ferent from the situation in Apis, worker control is evident for
many aspects of the intranidal and extranidal reproductive bi-
ology of Melipona stingless bees. As we are now able to point
to the evolutionary function of worker reproductive behav-
iours, study of their proximate mechanisms is urgently
needed.
Acknowledgement
Charles D. Michener and Mary-Jane West Eberhard gave very stimulat-
ing comments at the earlier version of this manuscript. Koos Boomsma
also read the previous version. Tom Wenseleers and an anonymous
reviewer supplied detailed suggestions for improvement. Frouke
Hofstede and Tong X. Chinh collaborated in collecting some of the data.
We are thankful to a number of persons in Trinidad and Tobago W.I. who
provided essential assistance for our studies. Gladstone Solomon, pres-
ident of the Tobago Apicultural Society and many other beekeepers on
the island of Tobago have much contributed to this work and have made
the field studies possible. We wish to thank the Tobago House of As-
sembly (Mr. Hugh McKennah, Secretary of Agriculture) and the com-
plete staff of the Agricultural Department at the Botanic Station, of
whom we particularly wish to mention Mr. Jerry Keens Dumas, Ad-
ministrator, and Mr. E. Harris, Chief Technical Officer. Mr. Edson
George, Bon Accord, Tobago, and Mr. Harrypersad Ramsamooj, Rio
Claro, Trinidad, supplied substantial support. Ms. Sheila McNab pro-
vided linguistic assistance.
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... However, in other species, like Brazilian M. quadrifasciata and M. favosa, cells containing males are usually placed in the center of the combs and gyne cells in the periphery (Koedam 1999). It is suggested that in species in which workers participate in male production, such as M. quadrifasciata and M. favosa, the workers lay eggs in batches in periods of "worker reproductive dominance" resulting in clustered male cells (Chinh et al. 2003;Sommeijer et al. 2003). ...
... This means that potentially one queen could result from each of four female larvae produced in the colony (Fig. 4.4). However, the natural production of queens recorded in several species of Melipona is below that prediction, ranging between 14 and 21% (Moo-Valle et al. 2001;Sommeijer et al. 2003;Morais et al. 2006). However, food conditions in colonies seems to influence the rate of queen production across time (Moo-Valle et al. 2001;Fig. ...
... Kerr In M. favosa, males are mostly sons of workers, and queen production is lowest, while in M. beecheii all males are produced by the queen and gyne production is highest. In the case of M. bicolor where Rf < 0.75, the percentage of gynes produced also increases as predicted (Wenseleers et al. 2003; 1950; Koedam 1999, Koedam et al. 2005Sommeijer et al. 2003). In contrast, in M. beecheii, in which all males are sons of the queen (Paxton et al. 2001), the production of queens is highest (14.6-19.8%, ...
Chapter
Like all Hymenopterans, bees are holometabolous; they pass through a series of anatomical and physiological changes, from larva to adult, called metamorphosis (Savard et al. Genome Res 16:1334–1338, 2006; Fig. 4.1). In holometabolous insects, there are five main stages in the ontogenetic development: egg, larva, prepupa, pupa, and adult or imago. After the larva hatches, it experiences a rapid growth. Because the rigid outer cuticle prevents the expansion and growth of the body, the larva needs to shed it in a series of molts or ecdysis. The regulation of growth and the ecdysis is under the effect of various hormones, the most important being the juvenile hormone (JH), insulin, and ecdysone (Hartfelder et al. Apidologie 37:144–163, 2006; Nijhout and Callier. Annu Rev Entomol 60:141–156, 2015). During the larval phase of the bee, there are four molts and five stages (Dade. Anatomy and dissection of the honeybee. International Bee Research Association, 1985). There is also a fifth molt between the prepupal and pupal phases, plus a final one between the pupal and the imago phases, making a total of six molts throughout the ontogenetic development.
... This evidence allows us to infer that Cuadro 1. Número promedio (± DE) de machos, obreras y reinas vírgenes en las secciones centro, medio y periferia de los panales Estas evidencias nos permiten inferir que en M. colimana la participación de las hembras en la producción de machos está restringida sólo para las reinas. Primeramente, en el análisis de los videos no se observaron evidencias de postura de huevos reproductivos por las obreras, siendo esta observación visual el primer paso para detectar esta posible actividad (10,15,20) . Posteriormente, el hecho de que no se observaron aglomeraciones de machos en los panales de cría, puede ser otra evidencia para sugerir que en M. colimana no existe actividad reproductiva de las obreras. ...
... Respecto a los porcentajes de individuos sexuados (el 22.46 % fueron machos y el 11.52 % resultaron reinas vírgenes), estos presentaron diferencias respecto a los datos que se han reportado en otras especies tropicales como M. favosa, M. trinitatis, M. asilvai, M. bicolor, M. subnitida y M. rufiventris, en donde el porcentaje de machos y reinas son más bajos que en M. colimana (20,23,24) . De la misma manera, en estudios recientes (25) , se reporta para M. bicolor una producción de machos de 4.7 %, que al compararlo con los in M. colimana the participation of females in the production of males is restricted only to queens. ...
... De la misma manera, en estudios recientes (25) , se reporta para M. bicolor una producción de machos de 4.7 %, que al compararlo con los in M. colimana the participation of females in the production of males is restricted only to queens. First of all, in the analysis of the videos, there was no evidence of the oviposition of reproductive eggs by the workers, this being the first step to infer the presence of workers with capacity of lay reproductive eggs (10,15,20) . Secondarily, the fact that there were no clusters of males in brood combs, may be other evidence to suggest that there is not reproductive activity of the workers in M. colimana. ...
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Melipona colimana es una abeja sin aguijón endémica de México que habita las regiones de clima templado del sur del estado de Jalisco. Se hicieron observaciones durante el otoño para contabilizar la emergencia de los individuos e inferir la posible participación de las obreras en la producción de machos. Se analizó el comportamiento de las obreras y la reina en el proceso de aprovisionamiento y oviposición (POP), se obtuvo la proporción de individuos en los panales de cría y su distribución espacial para detectar aglomeraciones de machos. En los análisis de los POP no se observaron evidencias de la actividad de obreras reproductivas. En los panales, el 65.9 % de los individuos que emergieron fueron obreras, el 22.4 % machos (sin registrarse aglomeraciones) y el 11.5 % resultaron reinas vírgenes. Se observó que la producción de individuos sexuados (machos y reinas) fue más alta que las especies tropicales, lo que pudiera ser una estrategia de esta especie para garantizar su reproducción en climas templados. El no tener evidencias visuales de la actividad de obreras reproductivas, junto con el hecho de que no se registraron aglomeraciones de machos en los panales de cría, sugiere que en esta especie y en esta temporada del año todos los huevos que se desarrollaron como machos provienen de la reina. Con los resultados de este trabajo se amplía el conocimiento de la biología particular de esta especie de clima templado y se hace una comparación con las especiesde distribución tropical.
... This evidence allows us to infer that Cuadro 1. Número promedio (± DE) de machos, obreras y reinas vírgenes en las secciones centro, medio y periferia de los panales Estas evidencias nos permiten inferir que en M. colimana la participación de las hembras en la producción de machos está restringida sólo para las reinas. Primeramente, en el análisis de los videos no se observaron evidencias de postura de huevos reproductivos por las obreras, siendo esta observación visual el primer paso para detectar esta posible actividad (10,15,20) . Posteriormente, el hecho de que no se observaron aglomeraciones de machos en los panales de cría, puede ser otra evidencia para sugerir que en M. colimana no existe actividad reproductiva de las obreras. ...
... Respecto a los porcentajes de individuos sexuados (el 22.46 % fueron machos y el 11.52 % resultaron reinas vírgenes), estos presentaron diferencias respecto a los datos que se han reportado en otras especies tropicales como M. favosa, M. trinitatis, M. asilvai, M. bicolor, M. subnitida y M. rufiventris, en donde el porcentaje de machos y reinas son más bajos que en M. colimana (20,23,24) . De la misma manera, en estudios recientes (25) , se reporta para M. bicolor una producción de machos de 4.7 %, que al compararlo con los in M. colimana the participation of females in the production of males is restricted only to queens. ...
... De la misma manera, en estudios recientes (25) , se reporta para M. bicolor una producción de machos de 4.7 %, que al compararlo con los in M. colimana the participation of females in the production of males is restricted only to queens. First of all, in the analysis of the videos, there was no evidence of the oviposition of reproductive eggs by the workers, this being the first step to infer the presence of workers with capacity of lay reproductive eggs (10,15,20) . Secondarily, the fact that there were no clusters of males in brood combs, may be other evidence to suggest that there is not reproductive activity of the workers in M. colimana. ...
Article
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Melipona colimana is a stingless bee endemic of Mexico that inhabiting temperate regions of the Southern State of Jalisco. Observations were made during the fall to infer the possible participation of the workers in the production of males. The behavior of workers and queen in provisioning and oviposition process (POP) was analyzed, the proportion of individuals was obtained in the brood combs and their spatial distribution for detecting clusters of males. In the analysis of POPs no evidence of reproductive labor activity of workers were observed. In the brood combs, 65.9 % of individuals that emerged were workers, 22.4 % males (without registering agglomerations) and 11.5 % were gynes. It was observed that the production of sexed individuals (males and gynes) was higher than tropical species, which could be a strategy of this species to ensure their reproduction in temperate climates. Having no visual evidence of the activity of reproductive workers together with the fact that no clusters of males in the brood combs were found, suggests that in this species at this time of year, all the eggs that developed as males come from the queen. With the results of this study, knowledge of the particular biology of this mountain stingless bee species is extended and a comparison with tropical species is made.
... In species of the genus Melipona, virgin queens are smaller than the workers and unlike other species of eusocial bees, there is a continuous production of queens across the colony's lifespan. Virgin queens represent 4-7 % of the colony (Imperatriz-Fonseca and Zucchi 1995; Koedam 1999;Sommeijer et al. 2003;Santos-Filho et al. 2006). The main explanation for the high production of queens was as a nest maintenance strategy due to physogastric queen mortality (Engels and Imperatriz-Fonseca 1990;Koedam et al. 1995), or as a future supply for the hive (Koedam et al. 1995). ...
... The main explanation for the high production of queens was as a nest maintenance strategy due to physogastric queen mortality (Engels and Imperatriz-Fonseca 1990;Koedam et al. 1995), or as a future supply for the hive (Koedam et al. 1995). Sommeijer et al. (2003) reported that a considerable proportion of excess queens are not eliminated by the workers but manage to safely leave the nest. They hypothesized that worker fitness was increased by the departure of the excess virgin queens when they reproduce outside their maternal nest. ...
Article
Full-text available
In queenright colonies of stingless bees of the genus Melipona, workers recognize, attack, and kill young virgin queens. For Melipona scutellaris, we observed that virgin queens were executed when they were between 5 and 9 days old, while newly emerged queens were not attacked. The faster movements of old virgin in relation to newly emerged might be responsible for attacks. It has been also hypothesized that cuticular hydrocarbons are the source of the signal used by workers to recognize virgin queens. We investigated whether newly emerged, 8 days old virgin and physogastric queens of M. scutellaris have different cuticular hydrocarbon profiles. Cuticular hydrocarbons of three ages were compared using gas chromatography-mass spectrometry. The cuticular hydrocarbon profiles varied by reproductive status and age. Changes in the cuticular hydrocarbons in virgin queens during aging suggest that these compounds, together with change in movement, may play a role in the recognition of virgin queens by workers prior to regicide.
... In M. subnitida and M. favosa, two species where the males can be produced by workers, male cells are frequently found clustered (Koedam, 1999; Koedam et al., 1999). A temporary " workerdominance " has been proposed to explain the clustering of males in M. subnitida and M. favosa (Chinh et al., 2003) and the reproductive laying worker behaviour is cyclical resulting in periods of worker male production (Sommeijer et al., 2003). The reduced frequency of male cell clustering in M. beecheii, a species where all males are queen produced (Paxton et al., 2001), give support to the hypothesis that the reproductive conflict between the queen and workers seem to be one of the main factors related to the distribution of male cells in other Melipona species where reproductive workers are common . ...
Article
Full-text available
The duration of the development phases of workers, males and gynes was studied in Melipona beecheii, an economically important stingless bee species in southern Mexico. We also determined if gynes and male cells were distributed in clusters on the combs as in other Melipona where laying workers exist. The results showed that the total length of development for the workers was 52.72 ± 1.28 days. In the case of the gynes and males, it was 50.80 (± 1.52) and 53.43 (± 1.12) days, respectively. We found that clustering of male cells in M. beecheii was an uncommon occurrence. We suggest that the main factor explaining the reduced frequency of male cell clusters is that males are not worker-produced in this species, compared to other species of Melipona in which males are worker-produced. Factors related to pollen availability could determine the presence of clustered males in some colonies of this species. stingless bees / Melipona / caste ontogeny / drone production / gyne production
... Regular brood cells with one queen-laid egg were more frequent (85.7%) than those with worker oviposition in S. xanthotricha, since queens have reproductive potential greater than workers. Females (diploid) are more frequent in the colony, whereas males (haploid) range from 0.1% to 18% individuals (Ferreira Junior et al., 2013;Sommeijer et al., 2003). T A B L E 1 Length (mean ± SD) of queen and worker-laid eggs that shared the same brood cell in the three colonies of Scaptotrigona xanthotricha The mean length of queen-laid eggs found alone in the brood cells of S. xanthotricha is similar to those found in multiple-eggs brood cells. ...
Article
The behavioural variation in bee workers raises questions about the reproduction in eusocial bees, as well as possible triggers for ovarian activation and oviposition. However, there are no data on possible differences between queen‐laid eggs found alone or together with worker‐laid eggs in a brood cell. This study evaluated the ploidy of eggs from queens found together with worker‐laid eggs in the brood cells of the stingless bee Scaptotrigona xanthotricha. In the brood cells with two eggs, there was a difference in size between them, with the smaller one being a similar size to those found in brood cells with only one egg. The frequency of diploid eggs in brood cells with one egg was 96.6%, whereas, in those with two or more, it was 39.3%. These results suggest that egg fertilization can be identified by workers, because when there is a worker‐laid egg, those from the queen are often haploid, supporting a prediction from Hamilton's theory of kin selection.
... Stingless bee colonies typically produce drones and virgin queens throughout the year (Roubik 1989;Sommeijer et al. 2003;Van Veen and Sommeijer 2000). Males leave the parental nest early in life and aggregate with other males, often in large mating swarms, which can comprise up to several thousand unrelated males. ...
Article
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Stingless bees (Hymenoptera, Apidae: Meliponini) represent a highly diverse group of social bees confined to the world's tropics and subtropics. They show a striking diversity of structural and behavioral adaptations and are important pollinators of tropical plants. Despite their diversity and functional importance, their ecology, and especially chemical ecology, has received relatively little attention, particularly compared to their relative the honeybee, Apis mellifera. Here, I review various aspects of the chemical ecology of stingless bees, from communication over resource allocation to defense. I list examples in which functions of specific compounds (or compound groups) have been demonstrated by behavioral experiments, and show that many aspects (e.g., queen-worker interactions, host-parasite interactions, neuronal processing etc.) remain little studied. This review further reveals that the vast majority of studies on the chemical ecology of stingless bees have been conducted in the New World, whereas studies on Old World stingless bees are still comparatively rare. Given the diversity of species, behaviors and, apparently, chemical compounds used, I suggest that stingless bees provide an ideal subject for studying how functional context and the need for species specificity may interact to shape pheromone diversification in social insects.
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Os machos de Melipona constituem elo importante na casta reprodutora nas colmeias e colônias destas abelhas-sem-ferrão. Nestas eles desempenham várias funções, mas a fundamental é contribuir, em parceria com princesas, na continuidade da espécie nos ambientes. Melipona eburnea Friese 1900 (“uruçu-beiço”) apresenta distribuição geográfica (incluindo Brasil) na América do Sul enquanto que M. seminigra merrillae Cockerell, 1920 (“uruçu-boca-de-renda”) é restrita a estados, especialmente, da Região Norte do Brasil. Ambas as espécies são promissoras para a Meliponicultura pela produtividade, facilidade da sua criação e manejo. Este estudo observacional objetivou conhecer, em condições de laboratório, alguns aspectos biológicos e etológicos de machos destas espécies. As colônias originais foram adaptadas à caixa de observação. Depois discos de cria nascentes foram obtidos destas e colocados em condições ideais de temperatura e umidade relativa. Imediatamente ao nascimento, machos foram marcados no tórax, com etiquetas coloridas e numeradas, usando-se cola atóxica. Em seguida, colocados nas colônias e aceitos pelas outras abelhas. As observações foram feitas na época chuvosa de 2003 (M. s. merrillae) e 2005 (M. eburnea), pela manhã, entre as 07:00-09:00 h e entre as 10:00-12:00 h. O tempo de permanência ou longevidade e a sobrevivência dos machos na colônia foi menor em M. eburnea e maior em M. s. merrillae. As curvas de sobrevivência foram do tipo convexa. Os machos das duas espécies, após abandonarem as colônias, não retornaram. Os ethos (comportamentos) detectados, foram classificados em sete categorias: limpeza corporal, imobilidade, mobilidade, incubação, trabalho com cerume, trofalaxis e corte à rainha.
Chapter
Stingless bee brood rearing is a complex process that involves workers performing a number of different jobs and requires coordination with the queen. After a new brood cell is finished, several workers regurgitate larval food into this cell, a process called mass provisioning. Shortly afterwards, the queen lays her egg on top of the larval food, immediately followed by the sealing of the cell (Sakagami 1982; Engels and Imperatriz-Fonseca 1990; Zucchi et al. 1999). Mass provisioning followed by oviposition and cell sealing is often considered to be an ancestral trait because it is also found in most solitary wasps and bees (Sakagami and Zucchi 1974; Sommeijer 1985; Roubik 1989). In stingless bees, however, cell building, provisioning, oviposition and cell sealing represent a highly integrated social process, with the queen acting as a pacemaker. This process differs considerably from brood rearing in honeybees where queens lay eggs into re-usable empty cells, which are then provisioned progressively for several days before the cell is sealed. The unique mode of brood rearing in stingless bees is thought to affect colony health, reproductive conflicts (Sect. 5.6) and the mating system (Chap. 4).
Article
Scanning electron microscopy is used to describe the eggs produced by the queen and the workers of 5. depilis, and to investigate possible morphological variations in the queen's eggs with different sizes. The eggs (81 queen's eggs and 20 worker's eggs, of which 13 are functional and 7 trophic) were collected from 7 colonies, from May 1998 to April 1999. Some eggs were measured before their preparation for microscopy. Queen's and worker's eggs of Scaptotrigona depilis were similar to the eggs of other studied species. Some queen eggs showed reduced numbers of pores or no pores at all in the micropylar region, suggesting that their absence may be related to the production of males by the queen. A significant negative correlation was found between the number of pores and egg length. These findings are in agreement with the assumption that males (queen's sons) originate from larger eggs. The results are discussed in terms of influence of the queen's oviposition rate on the size of the eggs, and possibly on male production.
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Microsatellite genotyping of workers from 13 species (ten genera) of stingless bees shows that genetic relatedness is very high.Workers are usually daughters of a single, singly mated queen. This observation, coupled with the multiple mating of honeybee queens, permits kin selection theory to account for many di¡erences in the social biology of the two taxa. First, in contrast to honeybees, where workers are predicted to and do police each other's male production, stingless bee workers are predicted to compete directly with the queen for rights to produce males. This leads to behavioural and reproductive con£ict during oviposition. Second, the risk that a daughter queen will attack the mother queen is higher in honeybees, as is the cost of such an attack to workers. This explains why stingless bees commonly have virgin queens in the nest, but honeybees do not. It also explains why in honeybees the mother queen leaves to found a new nest, while in stingless bees it is the daughter queen who leaves.
Article
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In Melipona favosa the court of workers surrounding the queen during the "extra-oviposition period" is formed principally by those workers who are actively participating in cell building in that period. These bees shuttle intensively between the cells, which they are building, and the distant resting queen. It is concluded that the gradual increase in court acts performed by these workers is of importance for the regulation of the locomotive pattern of the queen. The principal builders are the most active court bees at that time. The specific behaviour of the court workers should be considered as a form of "competitive communication". Similar ritualized court activity has been described for other stingless bee species. In certain species very striking worker-queen co-actions, termed by us as "bee-dances", have evolved. It is concluded that these "bee-dances" have developed for the purpose of conveying information to the queen and that this evolution is, in this group of bees, related to the peculiar temporal structure of oviposition.
Article
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A long-term study on the production of sexual offspring in relation to food stores was conducted in the stingless bee Melipona beecheii. Firstly, the production of sexuals was followed during one year in 10 colonies kept under natural conditions. Of the brood produced, 22.9% were males, and of all female brood, 14.6% were queens. Secondly, we measured the effect of experimentally manipulating the amount of food stores. One set of colonies started with 1.5 kg of food reserves and were regularly fed with pollen and nectar while another set were subjected to reduced food reserves of 0.5 kg, and were not given any extra food. Throughout the study, colonies with no treatment had brood and adults of both sexes all year round with no evidence of their presence being linked to swarming. Colonies with reduced food stores produced fewer males (0.7%) and queens (10.5%) than untreated colonies or colonies with enlarged food stores. The production of sexuals in colonies with enlarged food stores (23.4% males, 13.5% queens) did not differ significantly from that under natural conditions.¶We conclude that in Melipona only colonies that have accumulated large food stores produce sexuals that contribute to the reproductive population. This may lead to marked differences in the amount of sexuals produced by different colonies, although at the population level sexuals may be present all year round.
Article
A produção de machos em Nannotrigona (Scaptotrigona) postica e alguns aspectos correlacionados foram investigados e os resultados mostram que os fatores extrínsecos como temperatura e precipitação, através da sua importância na determinação das floradas e subsequente aumento na disponibilidade de mel e pólen, não são fatores determinantes imediatos da alta produtividade da colônia e da produção de machos, como consequência. Os dados também sugerem uma ausência de inibição da rainha no desenvolvimento ovariano das operárias e que a produção de machos ocorre independentemente da idade fisiológica da rainha. É possível que muitos outros fatores intrínsecos como alta densidade populacional da colônia (provavelmente conseqüente de condições favoráveis de estoque de pólen e mel) sejam mais importantes na determinação da produção de machos, uma vez que colônias que apresentam uma baixa densidade populacional não produzem machos, embora os ovários das operárias estejam sempre desenvolvidos. Além disso, a produção de machos parece estar ligada à oviposição das operárias devido à relação existente entre ocorrência de machos e células de cria contendo mais do que um ovo por célula, numa mesma colônia.
Chapter
In the highly eusocial honey bees (Apinae) and stingless bees (Meliponinae) marked caste syndromes have evolved. The typical queen and worker characteristics are different from one another not just with regard to the reproductive organs but include many other morphological, physiological, and behavioral differences as well. These striking caste distinctions are the result of postembryonic divergences in development which depend on ecological conditions, mainly on the external factor of larval nutrition. Caste development in social insects in general belongs to the widespread phenomena of insect polymorphism and, in accordance with environmental control, castes in bees were called ecomorphs (de Wilde and Wirtz 1974; de Wilde 1975). The trophogenic basis for caste induction is provided by the nursing workers, although in a colony brood rearing including gyne production is strongly influenced by the queen. The queen also rigidly controls all reproduction of the workers. On the other hand, her own reproductive output depends completely on the helper functions of the workers, her daughters.
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Workers and males of stingless bees (Meliponini) emerge from morphologically similar cells. Normally only one bee is reared in each brood cell, but in four Trigona postica colonies examined between September and February, 689 out of 2544 brood cells contained more than one egg. In these months the number of males is at a maximum.Nurse bees (workers) even in queenright colonies had developed ovaries and laid two distinct types of eggs: male-producing eggs (1.305 ± 0.33 mm long), and spherical eggs which served as food for the queen. The male eggs were laid in cells in which the queen had already laid, before these were sealed; the male larva survived, killing the other larva within the first 3 days of larval life.In normal queenright colonies the queen usually laid female-producing eggs (1.185 ± 0.18 mm long), but she also sometimes laid male-producing eggs (1.315 ± 0.33 mm long). On three occasions she was seen to lay a second egg in a cell, and these eggs were similar in length to the male- producing eggs.The production of males by the laying workers, which has not previously been described, increases the genetically active population of the colony.
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