Winter Cluster Research Articles

Glycogen in honeybee queens, workers and drones ( Apis mellifera carnica Pollm.)

Honey bees ( Apis mellifera carnica Pollm.) have low glycogen reserves in summer. Upon emergence drones have significantly larger amounts per unit weight when emerging, than workers; perhaps as adaption to the risk of not being fed as intensely as young workers. Maximum content was 0.23 mg for workers (28 d), and 0.59 mg for drones (after emergence). Workers have relatively constant glycogen contents during their life, and very young drones have more glycogen than older ones. Young queens are similar to workers. In workers and queens in summer the greatest amounts of glycogen are found in the thorax. When the bees start flying (6th–8th day of life), drones have the highest amounts in the head (probably to supply their eyes), and upon maturity, drones have the least glycogen in the abdomen. Workers in winter show different glycogen values depending on whether they are active bees from the core area (0.23 mg) or inactive ones from the outer surface of the winter cluster (0.37 mg). They use glycogen from the thorax and the abdomen for their ongoing energy need.

A method for continuous direct calorimetric measurements of energy metabolism in intact hornet (Vespa crabro) and honeybee (Apis mellifera) colonies

The heat production rates of an intact hornet (Vespa crabro) colony and a honeybee (Apis mellifera) winter cluster were measured by means of direct calorimetry. Two camping cold boxes with Peltier elements as cooling systems were used as simple and inexpensive differential calorimeters. The boxes had a volume of 24 I and sensitivities of between 6.8 mV W−1 and 14.8 mV W−1, depending on the experimental setup. They They were modified in such a way that the foragers had free access to the outdoor environment. The average daily heat production rate of the hornet colony ranged from 1.2 W at the end of the season in October up to 12.5 W at the stage of maximum biomass in August. The heat production rates of a honeybee winter cluster were measured in the following winter at ambient temperatures of 0–5°C. The maximum heat production rate was attained at 0°C (20.5 W) and the minimum heat production rate at 5°C (11.5 W). These results are compared with data for energy metabolism obtained respirometrically and by artificial heating of empty nests, respectively.

788 PB 024 RELATIONSHIP BETWEEN WINTER BUD CONSTRUCTION ANDFLOWER AND FRUIT NUMBER IN `CONCORD' AND `NIAGARA' GRAPEVINES

Winter buds of `Concord' and `Niagara' grapevines were dissected and their embryonic clusters scored to developmental stage. Stage was regressed against flower and fruit number per cluster the following year to see if flowering or fruiting potential could be gauged from bud morphology. `Concord' vines were either minimal-pruned (MP) or balance-pruned (BP) and non-irrigated or provided supplemental irrigation. `Niagara' vines were BP vines which were non-irrigated, irrigated, or nitrogen fertigated. Winter buds of MP `Concord' were significantly less developed than buds of BP vines, and flower and fruit number per cluster also significantly less. Irrigation did not affect bud construction or flower or fruit number per cluster in either pruning regime. Winter buds of `Niagara' had similar cluster stages in all treatments and there were similar flower and fruit number per cluster the following season. Within cultivar and year, there was a positive linear relationship between mean flower number or fruit number per cluster and mean stage of cluster differentiation within buds the previous dormant period. In `Concord', a given winter cluster stage allowed production of significantly more flowers and fruit in 1992 than it did in 1993. A bud's flowering potential thus varies from year to year and depends on factors not solely related to bud morphology.

Pollen utilization in non-breeding honeybees in winter

During the broodless period in winter, the pollen content of the gastrointestinal tract, the degree of pollen digestion and the proteolytic activity in the midgut were investigated in bees from the margin and from the centre of clusters of two colonies of Apis mellifera L. in Austria. In addition, the movement of bees within the winter cluster was examined. There was no difference in pollen content and proteolytic activity between bees from the centre or margin of the cluster, nor did the 2 groups show a preference for staying at the centre or on the margin of the winter cluster. Compared to 8–9-day-old bees in summer, the amount of pollen in the midguts was smaller by a factor of 100–1000, but the degree of pollen digestion in the midgut and the rectum was significantly greater; the proteolytic activity in the midgut was approximately a quarter. The more efficient utilization in spite of lower proteolytic activity might be due to pollen staying longer in the midgut. Foragers in summer also consume only minimal amounts of pollen but have a smaller degree of utilization than winter bees. The reduced pollen consumption rate, and efficient utilization in spite of lower proteolytic activity are useful adaptations to the reduced availability of pollen and reduced protein metabolism which bees experience during the winter.

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.

A model for heat production and thermoregulation in winter clusters of honey bees using differential heat conduction equations

A model is proposed for heat production and thermoregulation in the winter cluster of the honey bee Apis mellifera. It describes heat production within the cluster by an exponential decrease from the periphery to the centre, and takes into account threshold values for the central and the peripheral temperatures as well as changing diameters of the cluster. The results agree well with experimental data.

Thermal investigations of a honey bee colony: thermoregulation of the hive during summer and winter and heat production of members of different bee castes

The temperature at the centre, the periphery and the entrance of a honey bee colony (Apis mellifera carnica) was continuously determined during the summer season and the broodless time in winter. During the summer season the temperature in the brood nest averages 35.5°C with brief excursions up to 37.0°C and down to 33.8°C. Increasing environmental temperatures resulted in linear increases in the temperature of the hive entrance, its periphery and its centre. The temperature in the centre of an overwintering cluster is maintained at an average value of 21.3°C (min 12.0°C, max 33.5°C). With rising ambient temperatures the central temperature of a winter cluster drops whereas the peripheral temperature increases slightly. With decreasing external temperatures the peripheral temperature is lowered by a small amount while the cluster's centre temperature is raised. Linear relationships are observed between the central and the ambient temperature and between the central temperature and the temperature difference of the peripheral and the ambient temperatures. The slopes point to two minimum threshold values for the central (15°C) and the peripheral temperature (5°C) which should not be transgressed in an overwintering cluster. Microcalorimetric determinations of the heat production were performed on the three castes of the honey bee: workers, drones and queens of different ages. Among these groups single adult workers showed the highest heat production rates (209 mW·g−1) with only neglectible fluctuations in the heat production rate. Juvenile workers exhibited a mean heat production rate of 142 mW·g−1. The rate of heat production of adult workers is strongly dependent upon the number of bees together in a group. With more than 10 individuals weight-specific heat dissipation remains constant with increasing group sizes at a level approximately 1/17 that of an isolated bee. Differences are seen between the rates of virgin (117 mW·g−1) and laying (102 mW·g−1) queens. Laying queens showed less thermal fluctuations than virgin queens. High fluctuations in heat production rates are observed for drones. In both groups (fertile, juvenile) phases of high and extremely low activity succeed one another. The heat production of juvenile drones was 68 mW·g−1, that of fertile drones 184 mW·g−1 due to stronger locomotory activities.

APPLICATION OF CONTACT ACARICIDE AGAINST VARROA MITES WITH CONTAMINED PROTEINACEOUS FOOD

In an effort to find new ways to control varroatosis, malathion was mixed with dry pollen substitute in a concentration of 50 ppm. The preparation was put in a sickle-like arrangement in empty cells in the central area of the combs. These combs were put into 15 bee colonies during the period from November 1985 to March 1986. This kind of treatment was quite satisfactory to control Varroa mite without disturbance of bee colonies during the late season when the winter cluster was formed. The position of contaminated comb (s) within the cluster was an important factor for the effectiveness of the acaricide. About 50 °/ of the dead mites were found on the bottom of the hive during the first day and 80 °/ during the first three days after the application of the preparation. The toxicity of malathion was masked but not lost 10 days after the introduction of contaminated comb in the bee colony.

Why honeybees rear brood in winter. A theoretical study of the water conditions in the winter cluster of the honeybee, Apis mellifera

A model is presented describing the water conditions in the winter cluster of the honeybee, Apis mellifera. It is based on a specific view of how the thermoregulation of the winter cluster is accomplished. It assumes that the apparently coordinated thermoregulatory responses of the broodless winter cluster are results of the individuals' acting behaviourally and physiologically to regulate their own body temperature. The results include predictions about radial distribution of water evaporation and accumulation per bee, and cluster humidity, as a function of ambient temperature. The main conclusion is that the phenomenon of brood rearing in the winter cluster is likely to be a strategy which the bees have adopted in order to reduce their own water content when this has reached a specific level.

Thermoregulation in the winter cluster of the honeybee, Apis Mellifera

A model is presented based on the assumption that the apparently coordinated thermoregulatory responses of the broodless winter cluster of the honeybee, Apis mellifera , are results of the individuals acting behaviourally and physiologically to regulate their own body temperature. The predictive potential of the model is elucidated by a set of mathematically formulated relationships. The results include predictions concerning radial distributions of metabolic rate, and temperature profiles, as a function of ambient temperature. Furthermore, the apparently equal mass specific metabolic rate observed from weak and strong winter clusters is shown to be consistent with the proposed model. Consideration is also given to the generally accepted view of how the thermoregulation is accomplished, which is shown to give very unrealistic predictions.

Heat production in the winter cluster of the honeybee, Apis mellifera. A theoretical study

A mathematical model is presented, which predicts the distribution of metabolic rate per individual as a function of temperature in the winter cluster of the honeybee, Apis mellifera , under steady state conditions. The predicted distribution is discussed in relation to both evolutionary pressure and experimental data, and consideration is given to radial temperature profiles arising from qualitatively different metabolic rate distributions proposed in the literature.

The Thermology of Wintering Honeybee Colonies in 4-Colony Packs as Affected by Various Hive Entrances

SummaryDaily winter hive temperatures were recorded in multiple-packs of honeybee colonies (Apis mellifera) equipped with different types of hive entrance. Sixteen hives, each of two Langstroth boxes, were divided into 4 groups; these were then packed with insulation and tar-paper for wintering. In each group, two hives faced N and two S and the same treatment was used within each group. Treatments were: (1) bottom and top entrances (1 × 5 cm each); (2) fully open bottom entrance; (3) bottom and upper-side entrances (1 × 5 cm each); (4) bottom entrance (1 × 5 cm) and a 2·5-cm diameter auger-hole in the middle of the second chamber. During the 1979–1980 and 1980–1981 winters the temperature was recorded daily at 08.00 h using thermistors at 54 points in the SW hive in each of the groups. The ambient temperature fell as low as −38·8°C but the lowest hive temperature did not go below a range from −1° to −14°.All colonies in treatments 1 and 4 maintained a temperature of 30° or higher in the winter cluster th...

THE EPIDEMIOLOGY AND CONTROL OF NOSEMA DISEASE OF THE HONEY‐BEE

The proportion of honey‐bees infected with Nosema apis (Zander) declines in summer as the old infected bees die, for they cease to transmit their infection to the newly emerged individuals during the flying season. N. apis spores survive the summer on combs contaminated with infected faeces during the preceding winter. Although bees clean the combs during the summer, all infected material is not removed, and even well‐used brood comb, which has been repeatedly cleaned by bees, can carry infection. Only a few bees may contract infection in the autumn from these faeces, but they join the winter cluster and initiate the next outbreak of the disease. Transferring a colony on to clean comb early in the spring or summer removes the source of the disease, and it then disappears when all the old infected bees die.Old broodless comb can be sterilized quite simply by fumigation for a few days with the vapours of formalin or glacial acetic acid. Acetic acid is preferable, because it does not poison any honey or pollen in the combs. Formaldehyde can safely be used only with empty combs.The autumn is the best time for treating colonies chemotherapeutically, because the combs are then cleanest and the few bees which are infected can be cured during the winter. The drug can be incorporated in the syrup normally fed to colonies in autumn, and there is no risk of seriously contaminating subsequent honey crops. However, such treatment cannot eliminate the disease because sufficient spores remain on the combs for the disease to start again when the drug supplied in the winter stores is exhausted.