Jerry M. Marston

The digestion of dandelion pollen by adult worker honeybees

ABSTRACT. The digestion of dandelion (Taraxacum officinale) pollen by adult worker honeybees (Apis mellifera Linn.; Hymenoptera: Apidae) was initiated at the germination pores. 30 min after feeding, pollen had reached the anterior midgut and the germination pores had become swollen. This permitted further removal of protoplasm during the next 2 h of digestion as the pollen passed into the middle portion of the midgut. 3 h after feeding, pollen grains had reached the posterior midgut where some had ruptured to release both ‘naked’ protoplasm and masses of protoplasm but many remained intact or were only partially digested; undigested pollen grains passed unchanged to the rectum. The lipid‐rich pollenkitt layer was removed from the exine during digestion. Our studies indicate that dandelion pollen was not utilized completely by honeybees.

Mating behaviour of drone honey bees with queen models (Apis mellifera L.)

Abstract Wooden models of queen bees, when treated with queen pheromones and elevated (5 to 15 m), stimulated mating behaviour of flying drones. When sting chamber depths, of 1·6, 4·8 mm or ‘infinite’ were tested at diameters of 1·6, 2·4, 3·2 and 4·0 mm, respectively, the ‘mating’ frequency for the respective diameters (all depths pooled) was 4·6, 20·0, 46·7 and 44·8 per cent ( N =240), respectively, for 762 drones that mounted the models. Sting chamber dimensions affected the degree of drone genital eversion. The median time between mounting and eversion was 2·4 s. Prolonged mount duration (median=17·8 s) was observed when models had sting chambers too small to stimulate eversion. The data document the brevity of mating and the open sting chamber requirement.

Filtering mechanism of the honey bee proventriculus

ABSTRACT. The fine structure and function of a honey bees (Apis mellifera Linn.) proventriculus were studied by scanning electron microscopy and video‐recording. Our observations revealed that the proventriculus is used to engulf pollen and other particles which contaminate the nectar carried into the crop. The four lips are closed and opened, pulled backwards and straightened by the external circular muscles and internal longitudinal muscles. Combs of filiform‐hairs (70 μm in length) located on the margins of the lips ‘catch’ and filter particles from the fluid. By repeated filtering, opening and closing actions of the hairs and lips, particles are filtered and collected in pouches between the ventricular folds to form boluses and are eventually passed into the midgut. In the present experiment, particle sizes ranging from 0.5 to 100 μm in diameter, including dandelion pollen (Taraxacum officinale Web.), Torula yeast (Candida utilis Lodder et Kreger‐Van Rij), bee disease spores of Nosema apis Zander and Bacillus larvae White, and man‐made particles can be filtered by the hairs. Small particles (0.23 μm in diameter) filter through the hair and return back to the fluid. Large particles (100–200 μm in diameter) are caught between the stylets of the mouthparts and are not ingested. These observations suggest that the particle size plays an important role in determining what can be taken by the mouthparts and the proventriculus and what can later be utilized as a food source by the bee. The role of the proventriculus in disease transmission is also discussed.

Honeybee Pesticide Mortality: Intoxication Versus Acetylcholinesterase Concentration

SummaryBaseline acetylcholinesterase (AChE) activity was established in honeybees from three sources: foraging bees (Group I), upper brood nest area (Group 2), honey storage area (Group 3). AChE concentration was 70, 142·5 and 143·5 units/brain for Groups 1, 2 and 3, respectively, compared with a standard preparation of crystalline bovine erythrocyte AChE. Malathion oral LD50 in 1-M sugar syrup was 0·41, 0·82 and 0·87 μg/bee for Groups 1, 2 and 3, respectively, after 24 h exposure to the toxicant. AChE in vitro studies, in which bee head homogenate was the enzyme source, gave malaoxon molar I50 6·4 × 10−11M for Group 1 and 1·9 × 10−10M for Groups 2 and 3. These data indicate differences in AChE concentration, rather than differences in enzymatic activity, in bee brain at different stages of maturity. Bees with less brain enzyme (foragers, Group 1) were more susceptible to organophosphorus AChE inhibitors than younger bees (Groups 2 and 3), which had higher concentrations of brain enzyme.

Distribution and Foraging Activities of Honeybees During Almond Pollination

SummaryA magnetic capture-recapture system was used to study the distribution and foraging activities of 1513 honeybees from 60 apiaries in 5 almond orchards (area 9 km2) in California, USA. Bees tended to forage near the apiary from which they flew. Where there was intense competition, owing to high hive densities, foragers dispersed to orchards containing fewer hives. There were significantly more foragers in populous than in small colonies, but the distance at which they foraged was not affected by colony size. The mean nectar load was 5·9 μl, and its mean sugar concentration 43·9%. Pollen collection and foraging distance were similar for Hy-Queen and for common Italian stocks.

The Inter- and Intra-Orchard Distribution of Honeybees During Almond Pollination

SummaryThe distribution of foraging honeybees was determined, by a magnetic capture-recapture system, for 703 colonies in 9 almond orchards within an area of 9 km2 near Dixon, California. Flight distances and directions were recorded for 2052 bees. The mean foraging range of bees from various apiaries within orchards varied from 80 to 261 m; it depended greatly upon the spatial distribution of apiaries. Inter-orchard flights were appreciable from orchards with high colony densities (c. 8/ha) to orchards without colonies or with low colony densities.In large production areas, pollination districts are suggested for co-ordinating the distribution of colonies for maximal foraging efficiency, and for equitable distribution of colony costs among the growers.

Ultrastructure of the freeze-etched spore of Ascosphaera apis, an entomopathogenic fungus of the honeybee Apis mellifera.

Abstract The freeze-fractured outer surface of the spore wall of Ascophaera apis is covered with granules which are 21.5 nm in diameter. The cross-fractured spore wall consists of subunits which are 9 nm in diameter. The inner surface of the spore wall is granular and has many stud-like projections measuring approximately 120 nm long × 26 nm wide. The convex face of the spore membrane carries many particles as well as many depressions which are complementary to the projections on the inner surface of the spore wall. The nucleus possesses double nuclear membranes which contain numerous well-defined nuclear pores. In the cytoplasm of the spore there are many mitochondria which have well-defined cristae and many particles on the internal membranes. The sporoplasm contains many lipid droplets which possess concentric smooth-surfaced lamellae.

The Effects of Low Doses of Gamma Irradiation on the Ultrastructure of Nosema Apis in Vitro

SummaryInfected midguts of honeybees in the tissue culture medium received low dose gamma irradiation. After irradiation dramatic ultrastructural changes took place in various developmental stages of Nosema apis. In the irradiated sporoblasts and sporont stages, laminated endoplasmic reticulum was absent; instead there were numerous vacuoles in the cytoplasm. There were fewer nuclear pores in the nuclear envelope of irradiated organisms than in the untreated group. The diameter of the nuclear pore was larger in the irradiated group. The polar filament was not developed in the irradiated sporoblast. There were very few mature spores developed in the midgut 48 h after irradiation.

In vitro activity of 15-azasterol (A25822B) against chalkbrood pathogen Ascosphaera apis in the honey bee

The antifungal agent 15-azasterol A25822B was examined for effects on the growth and development of Ascosphaera apis. The minimum inhibition concentration (MIC) of azasterol against A. apis was 1 μm. Growth and development of A. apis was completely controlled at this concentration. At a concentration of 0.01 μm growth of A. apis was retarded and although sporocysts were formed developing spores were not be able to reach maturation. A major effect of azasterol at this low concentration was the accumulation of lipid in the hyphae, sporocysts and immature spores. In addition it caused a conformational change in mitochondria and damage to the spore membrane structure. On the basis of these results, further investigations of azasterol for the treatment of chalkbrood disease in the honey bee are warranted.