Temporal resource partitioning and climatological influences on colony flight and foraging of stingless bees (Apidae; Meliponini) in Ugandan tropical forests

We studied the flight activity of two stingless bee species (Meliponula ferruginea and Meliponula nebulata) and the environmental factors influencing their flight. Two morphs of M. ferruginea were studied: M. ferruginea (brown) in Budongo forest and M. ferruginea (black) in Bwindi Park. The two bee species exited their nests in characteristically distinct foraging bouts suggesting that the recruitment methods used may be direct leading or ‘piloting’. The number of individuals in a returning bout was less than that in an exiting bout suggesting recruits do not follow experienced foragers the whole distance to food source, a phenomenon referred to as ‘partial piloting’. Flight period of M. ferruginea (black) and M. nebulata in Bwindi was restricted to a few hours each day. Meliponula nebulata foraged in the drizzle; a survival strategy, which could promote its reproductive fitness. Nectar and pollen foraging took place throughout the day while the removal of debris was greater in the late hours of the morning. Increased temperature resulted in significant increase in number of exiting bees. There was increase in number of exiting bees with decrease in humidity up to an optimal of 78% thereafter, increase in humidity resulted in reduced number of exiting bees.     

Foraging behavior of Melipona rufiventris Lepeletier (Apinae; Meliponini) in Ubatuba, SP, Brazil.

This study describes how the foraging activity of Melipona rufiventris is influenced by the environment and/or by the state of a colony. Two colonies were studied in Ubatuba, SP (44 degrees 48 W and 23 degrees 22 S) from July/2000 to June/2001. These colonies were classified as strong (Colony 1) and intermediate (Colony 2) according to their general conditions: population and brood comb size and number of food pots. The bees were active from dawn to dusk. The number of pollen loads presented a positive correlation with relative humidity (r(s) = 0.401; p <0.01) and was highest between 70 and 90%. However, it was negatively correlated with temperature (r(s) = -0.228; p <0.01) showing a peak between 18 and 23 degrees C. The number of nectar loads presented a positive correlation with temperature (r(s) = 0.244; p <0.01) and light intensity (r(s) = 0.414; p <0.01); it was greater between 50 and 90% of relative humidity and 20 and 30 degrees C of temperature. They collected more nectar than pollen throughout the day, and were more active between 6 and 9 hours. Workers from Colony 1 (strong) collected nectar in greater amounts and earlier than those from Colony 2 (intermediate). The number of pollen, nectar and resin loads varied considerably between the study days. Peaks of pollen collection occurred earlier in months with longer days and in a hotter and more humid climate. The foraging behavior of M. rufiventris is probably affected by the state of the colony and by environmental conditions, notably temperature, relative humidity, light intensity and length of the day.     

Environmental influences on flight activity of USDA-ARS Russian and Italian stocks of honey bees (Hymenoptera: Apidae) during almond pollination

Differences in flight activity and in the percentages of pollen foragers between commercially managed honey bees, Apis mellifera L. (Hymenoptera: Apidae), of two stocks (USDA-ARS Russian, n = 41 colonies; and Italian, n = 43 colonies) were evaluated in an almond, Prunus dulcis (Miller) D. A. Webb, orchard in Kern Co., CA, during February and March 2002. Flight activity was measured by taking 1-min counts of bees exiting colonies on each of 9 d. Flight activity was best predicted with a model containing the effects of colony size (populations of adult bees and sealed brood), temperature, time of day, the interaction of adult bee population with temperature, and the interaction of adult bee population with time of day. Flight increased linearly with adult bee and brood population, had a quadratic relationship with temperature (increasing, but less so at higher temperatures), and had a quadratic relationship with time of day (decreasing, but less so at later times). Larger colonies had more response to changing temperatures and less response to different times of day than small colonies. Bee type had no direct influence on flight activity at any given colony size, temperature, or time of observation or when evaluated using a reduced data set retaining 34 Italian colonies and 32 Russian colonies whose mean sizes were equal. Overall, however, Russian colonies were less populous by about one-fourth and so fielded on average 71% of the foragers that Italian colonies did. Pollen collection was measured by capturing returning foragers on 4 d. The percentages of foragers with pollen were not different for the bee types.     

Floral preferences and climate influence in nectar and pollen foraging by Melipona rufiventris Lepeletier (Hymenoptera: Meliponini) in Ubatuba, São Paulo state, Brazil

We describe the environment effects on the amount and quality of resources collected by Melipona rufiventris Lepeletier in the Atlantic Forest at Ubatuba city, S?o Paulo state, Brazil (44o48'W, 23o22'S). Bees carrying pollen and/or nectar were captured at nest entrances during 5 min every hour, from sunrise to sunset, once a month. Pollen loads were counted and saved for acetolysis. Nectar was collected, the volume was determined and the total dissolved solids were determined by refractometer. Air temperature, relative humidity and light intensity were also registered. The number of pollen loads reached its maximum value between 70% and 90% of relative humidity and 18oC and 23oC; for nectar loads this range was broader, 50-90% and 20-30oC. The number of pollen loads increased as relative humidity rose (rs = 0.401; P < 0.01) and high temperatures had a strong negative influence on the number of pollen loads collected (rs = -0.228; P < 0.01). The number of nectar loads positively correlated with temperature (rs = 0.244; P < 0.01) and light intensity (rs = 0.414; P < 0.01). The percentage of total dissolved solids (TDS) on nectar loads positively correlated with temperature and light intensity (rs = 0.361; P < 0.01 and rs = 0.245; P < 0.01), negatively correlated with relative humidity (rs = -0.629; P < 0.01), and it increased along the day. Most nectar loads had TDS between 11% and 30%, with an average of 24.7%. The volume measures did not show any pattern. Important pollen sources were Sapindaceae, Anacardiaceae, Rubiaceae, Arecaceae, Solanaceae and Myrtaceae; nectar sources were Sapindaceae, Fabaceae, Rubiaceae, Arecaceae and Solanaceae.     

Flight activity of USDA-ARS Russian honey bees (Hymenoptera: Apidae) during pollination of lowbush blueberries in Maine

Flight activity was compared in colonies of Russian honey bees, Apis mellifera L. (Hymenoptera: Apidae), and Italian bees during commercial pollination of lowbush blueberries (principally Vaccinium angustifolium Aiton) in Washington Co., ME, in late May and early June in 2003 and 2004. Colonies of the two stocks were managed equally in Louisiana during autumn through early spring preceding observations in late spring each year. Resulting average populations of adult bees and of brood were similar in colonies of the two bee stocks during pollination. Flight during pollination was monitored hourly on 6 d each year by counting bees exiting each colony per minute; counts were made manually with flight cones on 17 colonies per stock in 2003 and electronically with ApiSCAN-Plus counters on 20 colonies per stock in 2004. Analysis of variance showed that temperature, colony size (population of adult bees or brood), and the interaction of these effects were the strongest regulators of flight activity in both years. Russian and Italian bees had similar flight activity at any given colony size, temperature, or time of day. Flight increased linearly with rising temperatures and larger colony sizes. Larger colonies, however, were more responsive than smaller colonies across the range of temperatures measured. In 2003, flight responses to varying temperatures were less in the afternoon and evening (1500-1959 hours) than they were earlier in the day. Russian colonies had flight activity that was suitable for late spring pollination of lowbush blueberries.     

Western honey bee (Apis mellifera L.) attraction to commercial pollen substitutes and wildflower pollen in vitro

Many beekeepers feed their western honey bee (Apis mellifera) colonies artificial pollen substitutes to provide colonies with adequate nutrition during times of limited pollen quantity or quality. We provided caged worker bees commercially available pollen substitutes (AP23, MegaBee, UltraBee) and wildflower pollen in a choice-test to determine their relative attraction to/preference for the diets. We measured diet consumption by honey bees and observed honey bee behaviour to evaluate bee preferences for certain diets. The bees interacted with and consumed more wildflower pollen than they did any of the commercially available pollen substitutes. Our data suggest that bees have a strong preference for wildflower pollen over commercially available pollen substitutes.     

Seasonal patterns of foraging activity in colonies of the African honey bee,Apis mellifera scutellata,in Africa

Summary Seasonal foraging patterns were investigated using six observation colonies maintained in the Okavango Delta, Botswana. Pollen collection, flight from the hive, and recruitment for pollen and nectar sources occurred throughout the 11 months of the study. However, the distribution of foraging activity throughout the day changed seasonally. Colonies emphasized recruitment for pollen sites throughout most of the year. Brood production occurred in all months except May, and there was a significant, positive correlation between the proportion of recruitment activity devoted to pollen sources and the amount of brood comb in the colonies. The seasonal foraging patterns ofscutellata in the Okavango were similar to those of Africanized honey bees in the neotropics. The extended foraging season and emphasis on pollen collection may be associated with the high swarming rates and migrational movements of tropical honey bees.     

Behavior and pollination efficiency of Nannotrigona perilampoides (Hymenoptera: Meliponini) on greenhouse tomatoes (Lycopersicon esculentum) in subtropical México

The acclimation, foraging behavior, and pollination efficiency of stingless bees of the species Nannotrigona perilampoides Cresson were evaluated in tomato (Lycopersicon esculentum Mill.) plants cultivated in two greenhouses. The greenhouses were divided into three areas of 16 m2, and one of the following treatments was used for pollination: stingless bees (SB), mechanical vibration (MV), and no pollination (NP). Observations were conducted once a week from 0800 to 1600 hours during 2 mo. The acclimation of the bees to the greenhouses was estimated by the number of bees that did not return to the hive (lost bees) and by comparing the population of the colonies (brood and adults). The foraging activity of the bees across the day was evaluated by comparing the number of foragers per hour. The influence of environmental variables on the foraging activity was also analyzed. The pollination efficiency was compared among treatments through the percentage of fruit set, weight of individual fruit, kilograms of fruit produced per square meter, and the number of seed per fruit. The bees started foraging on the flowers approximately 7 d after the colonies were introduced to the greenhouse. There was a decline in the population of the colonies across the experiment, but colonies did not die out. Correlations of environmental variables with the foraging activity of the bees showed that none of them had a significant influence on pollen foraging. However, water collection was positively correlated with the temperature and negatively correlated with the humidity inside the greenhouse. The estimation of the pollination efficiency per treatment showed that there were significant differences in fruit set in SB (83 +/- 4.2) and MV (78.5 +/- 6.4) compared with NP (52.6 +/- 7.6). However, the average weight of the fruit was similar for the three treatments (65 g). There were significant differences for seed number in SB (200 +/- 15.3) and MV (232 +/- 21.4) compared with NP (120 +/- 16.6). The productivity in kilograms of fruit per square meter was higher in SB (5.72 +/- 0.61) and MV (5.66 +/- 0.58 kg) compared with NP (3.34 +/- 0.72). The number of seed was positively correlated with the weight of the fruit. We conclude that the use of Nannotrigona testaceicornis Rondani, for pollinating greenhouse tomatoes in tropical climates, could be an alternative to the use of highly defensive African-derived Apis mellifera or non-native bumble bees (Bombus spp.). However, more research is needed to evaluate the cost/benefit on large-scale greenhouse pollination using N. perilampoides Cresson against other bee species and pollination methods.     

Honey bee (Apis mellifera) preference towards micronutrients and their impact on bee colonies

Honey bees are important pollinators and take micronutrients from different natural floral resources and turbid water to adequately meet their nutritional requirements. But the role of micronutrients for honey bee health is not well understood. Here, the present study was conducted to determine honey bees' micronutrients preference in summer and winter seasons. Also, the impact of micronutrients on foraging behaviour and brood increase was studied in different honey bee colonies. The results elucidated that honey bees exhibited a strong preference for a salt solution compared to deionized water during the summer and winter seasons. However, there was a notable switch in salt preference between seasons. Overall, honey bees showed significantly more foraging activity, more pollen collection, and increased brood area after sodium consumption compared to other minerals in the summer season. Further, pollen collection and brood area were significantly higher after the use of potassium in the winter season. Thus, the food preference of honey bees is strongly linked with the seasons and the availability of the floral resources. Our data suggested that honey bees may seek specific nutrients during variation of the seasonal conditions.     

Regulation of nectar collection in relation to honey storage levels by honey bees, Apis mellifera

Honey bees collect distinct nutrient sources in the form ofnectar (energy) and pollen (nitrogen). We investigated the effectof varying energy stores on nectar and pollen foraging. We foundno significant changes in nectar foraging in response to changesin honey storage levels within colonies. Individual foragersdid not vary activity rates or nectar load sizes in responseto changes in honey stores, and colonies did not increase nectarintake rates when honey stores within the hive were decreased.This result contrasts with pollen foraging behavior, which isextremely sensitive to colony state. Our data show that individualforaging decisions during nectar collection and colony regulationof nectar intake are distincdy different from pollen foraging.The behavior of honey bees illustrates that foraging strategy(and therefore foraging models) can incorporate multiple currencies,including both energy and protein intake.[Behav Ecol 7: 286–291(1996)]     

Eine schnelle biologische Methode zum Nachweis der Phytotoxizität von Wirkstoffen in Pestiziden mit Hilfe eines Blattaufstiegtestes bei Sinapis alba L. Kotyledonen: (Kurze Mitteilung)

The present work was carried out to study the relationship between brood rearing activity, bee density and stored pollen grains. Fifteen colonies, 1st. Carniolan hybrid nearly in equal strength were put under investigation from June 1994 to May 1995.

The results revealed that the major peak of brood activity and higher rate of stored pollen were in May, consequently the maximum number of house bees was recorded during June and July. However no correlation existed, the lowest production of brood, bees and gathered pollen occurred during February. It was found that high significant differences were in quantity of brood and house bees, while low significant differences were in quantity of stored pollen. Correlations between brood activity, house bees density and stored pollen were observed in winter.     

Comparison of the activity and productivity of Carniolan (Apis mellifera carnica Pollmann) and Yemeni (Apis mellifera jemenitica Ruttner) subspecies under environmental conditions of the Al-Ahsa oasis of eastern Saudi Arabia

This study was conducted at the apiary of the Agricultural and Veterinary Training and Research Station of King Faisal University in the Al-Ahsa oasis of eastern Saudi Arabia. We performed a comparison between Carniolan (Apis mellifera carnica Pollmann) and Yemeni (Apis mellifera jemenitica Ruttner) honeybee races to determine the monthly fluctuations in foraging activity, pollen collection, colony growth and honey yield production under the environmental conditions of the Al-Ahsa oasis of eastern Saudi Arabia. We found three peaks in the flight activity of the two races, and the largest peaks occurred during September and October. Compared to Carniolan bee colonies, the performance of Yemeni bee colonies was superior in terms of stored pollen, worker and drone brood rearing, and the adult population size. The Carniolan bee colonies produced 27.77% and 27.50% more honey than the Yemeni bee colonies during the flow seasons of alfalfa and sidir, respectively, with an average increase of 27.64%. It could be concluded that the race of bees is an important factor affecting the activity and productivity of honeybee colonies. The Yemeni bee race produced more pollen, a larger brood and more bees, which exhibited a longer survival. The imported Carniolan bees can be reared in eastern Saudi Arabia, but the Yemeni bee race is still better.     

The influence of brood on the pollen consumption of worker bees (Apis mellifera L.)

(1) In midgut dry weight (tissue plus contents) of worker bees we found a representative parameter for pollen consumption. Midguts of bees of successive ages were analyzed and correlated with various parameters. The relative proportions of sugar, protein and water were either constant or negatively correlated with midgut weight. Only the relative pollen weight (percent of midgut dry weight) increased. (2) To investigate the influence of different levels of brood on pollen consumption of individual bees, midgut dry weights from 2 normally breeding control colonies and 2 brood-reduced experimental colonies were analyzed. In bees from control colonies the pollen consumption increased up to the nursing age (3-10d), remained on an elevated level in middle-aged-bees (10-18d) and decreased relatively sharply towards the foraging ages (>21d). When queens were caged in the experimental colonies, the following decline of brood cells affected the consumption of pollen differently. After 6 days of caging, with a reduction of open brood only, no effect was seen. After 15 days, and even more pronounced after 23 days when no brood was present, the pollen consumption in young and middle-aged (10, 14, 18d) worker bees was significantly reduced, while it was clearly elevated in older bees. We discuss pollen consumption as an adaptation to reduced necessity to nurse brood in young and middle-aged bees, and to enhance life span in older animals.     

Development of early infestations by the miteVarroa jacobsoni in honey-bee (Apis mellifera) colonies in cold climates

The development of an infestation by five to eight introduced adult females ofVarroa jacobsoni Oud. in 35 honey-bee (Apis mellifera L.) colonies was monitored for 16 months with no outside source of infestation. Calculations on the size of the mite populations were based on collection of debris, samples of bees and brood, and estimates of number of bees and broodcells during the summer. In the winter, only dead bees and debris were collected. Samples were taken at 3-week intervals. Data indicated that the mite population probably could increase more than 100 times within one summer, and more than ten times between years, in a climate with a brood-rearing period of less than five months. A large variation in mite population increase existed between colonies. The winter mortality of mites that die with the host or drop from the winter cluster has a large influence on the population dynamics of the mite. Data also indicated that the simple method of counting mites in hive debris is a useful parameter for monitoring the population development ofVarroa in colonies with hatching brood.     

Dwindling pollen resources trigger the transition to broodless populations of long-lived honeybees each autumn

Abstract.  1. Each autumn in northern regions, honeybee colonies shift from populations of short-lived workers that actively rear brood to broodless populations of long-lived winter bees. To determine if dwindling pollen resources trigger this transition, the natural disappearance of external pollen resources was artificially accelerated or delayed and colonies were monitored for effects on the decline in brood-rearing activity and the development of populations of long-lived winter bees.
2. Delaying the disappearance of pollen resources postponed the decline in brood rearing in colonies. Colonies with an extended supply of pollen reared workers longer into October before brood rearing ended than control colonies or colonies for which pollen supply was cut short artificially in autumn.
3. Colonies with extended pollen supply produced more workers throughout autumn than colonies with less pollen, but the development of the population of long-lived winter bees was delayed until relatively later in autumn. Colonies produced similar numbers of winter bees, regardless of the timing of the disappearance of pollen resources.
4. Mean longevity of autumn-reared workers was inversely related to the amount of brood remaining to be reared in colonies when workers eclosed. Consequently, long-lived workers did not appear in colonies until brood rearing declined, which in turn was controlled by the availability of pollen.
5. Dwindling pollen resources provide a powerful cue that initiates the transition to populations of broodless winter bees because it directly affects the brood-rearing capacity of colonies and indirectly indicates deteriorating environmental conditions associated with the approach of winter.     

Pollen and nectar as a reward in the basal epidendroid Psilochilus modestus (Orchidaceae: Triphoreae): A study of floral morphology, reproductive biology and pollination strategy

Psilochilus modestus Barb. Rodr. is a basal epidendroid orchid occurring in both the semi-deciduous and Atlantic rain forests of the state of São Paulo, southeastern Brazil. This species presents a perfect flowering synchrony within populations, since all the mature buds of each plant open simultaneously in the morning hours of the same day. These flowers are available only for 1 day and are pollinated by several species of small solitary and social native bees. These bees exploit both pollen and nectar as a reward. The bees collecting pollen promote a higher fruit set and perform mainly self-pollination while those collecting nectar, which are less numerous, are responsible for an increase in cross-pollinations. P. modestus is self-compatible but pollinator dependent. Natural fruit set (open pollination) is low when compared with the numbers obtained under manual self- and cross-pollination. Low fruit set in natural conditions is related to deficient pollen transfer, and pollinator inefficiency seems to be the main factor. Some factors, such as the small amount of nectar produced, the low number of flowers per inflorescence and their availability for 1 day only added to the perfect flowering synchrony seem to be responsible for the increase of cross-pollinations. The offering of both pollen and nectar as a reward can represent a transitional condition in basal Epidendroideae. Based on floral morphology, reward production and pollinator behavior, the relationship of P. modestus with the basal and most derived groups within Orchidaceae is discussed.     

Rearing of Non-Descendant Offspring in an Allodapine Bee, Exoneura bicolor Smith (Hymenoptera: Apidae: Xylocopinae): A Preferred Strategy or Queen Coercion?

In heathland populations of the Australian allodapine bee Exoneura bicolor , the presence of overlapping broods in some colonies creates opportunities for eusocial-like sib rearing. By artificially orphaning colonies in observation nests, we investigated whether sib-rearing by some older daughters occurs in the absence of any potential for coercion by parental females. We found strong evidence for sib-rearing in the absence of parental females in 40% of our nests and weaker evidence in another 40%. of those colonies with strong evidence of sib-rearing, 65% of such rearing occurred in nests where there was also no opportunity for coercion by adult siblings. These results indicate that sib-rearing in E. bicolor does not require coercion by adult nestmates. A variety of factors that may make sib-rearing a preferred strategy in the absence of coercion are discussed.     

Division of labour within flowers: heteranthery,a floral strategy to reconcile contrasting pollen fates

In many nectarless flowering plants, pollen serves as both the carrier of male gametes and as food for pollinators. This can generate an evolutionary conflict if the use of pollen as food by pollinators reduces the number of gametes available for cross‐fertilization. Heteranthery, the production of two or more stamen types by individual flowers reduces this conflict by allowing different stamens to specialize in ‘pollinating’ and ‘feeding’ functions. We used experimental studies of Solanum rostratum (Solanaceae) and theoretical models to investigate this ‘division of labour’ hypothesis. Flight cage experiments with pollinating bumble bees (Bombus impatiens) demonstrated that although feeding anthers are preferentially manipulated by bees, pollinating anthers export more pollen to other flowers. Evolutionary stability analysis of a model of pollination by pollen consumers indicated that heteranthery evolves when bees consume more pollen than should optimally be exchanged for visitation services, particularly when pollinators adjust their visitation according to the amount of pollen collected.     

A Temporal Dimension to the Influence of Pollen Rewards on Bee Behaviour and Fecundity in Aloe tenuior

The net effect of pollen production on fecundity in plants can range from negative – when self-pollen interferes with fecundity due to incompatibility mechanisms, to positive – when pollen availability is associated with increased pollinator visitation and fecundity due to its utilization as a reward. We investigated the responses of bees to pollen and nectar rewards, and the effects of these rewards on pollen deposition and fecundity in the hermaphroditic succulent shrub Aloe tenuior. Self-pollinated plants failed to set fruit, but their ovules were regularly penetrated by self-pollen tubes, which uniformly failed to develop into seeds as expected from ovarian self-incompatibility (or strong early inbreeding depression). Bees consistently foraged for pollen during the morning and early afternoon, but switched to nectar in the late afternoon. As a consequence of this differential foraging, we were able to test the relative contribution to fecundity of pollen- versus nectar-collecting flower visitors. We exposed emasculated and intact flowers in either the morning or late afternoon to foraging bees and showed that emasculation reduced pollen deposition by insects in the morning, but had little effect in the afternoon. Despite the potential for self-pollination to result in ovule discounting due to late-acting self-sterility, fecundity was severely reduced in artificially emasculated plants. Although there were temporal fluctuations in reward preference, most bee visits were for pollen rewards. Therefore the benefit of providing pollen that is accessible to bee foragers outweighs any potential costs to fitness in terms of gender interference in this species.     

Colony pollen reserves affect body size,sperm production and sexual development in males of the stingless bee <Emphasis Type="Italic">Melipona beecheii</Emphasis>

The production of male sexual offspring by social insect colonies is often strongly seasonal or resource-dependent. In stingless bees, males are produced in smaller numbers under conditions of low colony food reserves; whether such males are negatively affected in traits related to reproductive success is not known. We compared body size, sperm production and sexual maturity in Melipona beecheii males reared with experimentally supplemented or reduced pollen reserves, but with otherwise equal numbers of workers and equal quantities of honey reserves. We also studied the same traits in males collected from non-manipulated colonies with pollen reserves intermediate between the supplemented or reduced groups but with more workers and honey reserves. Males reared under experimentally reduced pollen reserves had significantly smaller bodies and lower sperm counts compared to those reared in colonies with experimentally supplemented pollen reserves. There was also a significantly positive relationship between the number of sperm and body size in males across all colony treatments. The maximum number of sperm in seminal vesicles was recorded 2 days later in males from colonies with reduced pollen compared to males from colonies with supplementary pollen. Males from non-manipulated colonies were intermediate in size, sperm count and speed of maturation. Our study documents for the first time the existence of large size variation in males of stingless bees that is related with the amount of pollen reserves in their natal colony. We conclude that a colony’s pollen reserves have a major impact on male body size, sperm production and speed of sexual maturity in this stingless bee, which may be the case in other social insects. Stingless bees are a good model system to study the balance between colony-level selection and individual-level selection on male sexually selected traits such as body size.