Walter C. Rothenbuhler

Behaviour genetics of nest cleaning in honey bees. I. Responses of four inbred lines to disease-killed brood ☆

Abstract Eleven colonies of honey bees representing four inbred lines were tested to learn their behaviour toward American foulbrood-killed larvae and pupae in their broodnests. To set up the experiments, about 2,900 larvae were exposed to Bacillus larvae spores suspended in water, and 2,600 control larvae were treated with water alone. All brood cells were observed, daily in most cases, for about two weeks, to learn whether or not the adult bees had removed the brood contained therein. By the end of the experiment, two of the inbred lines, with a history of resistance to American foulbrood, had removed from their cells all but three individuals of the several hundred which did not survive. The two other inbred lines, with a history of susceptibility to American foulbrood, allowed hundreds of individuals dead of the disease to remain in the broodnest. Thus a striking difference in behaviour toward brood dead of American foulbrood was demonstrated.

Laboratory and Field Measurements of Hoarding Behaviour in the Honeybee

SummaryHoarding behaviour was measured in the laboratory by putting 50 newly emerged bees into a small box-like cage and noting the time the bees required to remove 20 ml of sugar syrup from their feeder, some of which was consumed and some stored in their comb. Bees from brood of the same colony usually required similar times; bees from brood of different colonies varied widely. The time required by bees from 21 colonies in these laboratory tests was negatively correlated with the weight gained by the colonies in the field (r = −0·33). It is suggested that the laboratory test may therefore provide an indication of colony hoarding behaviour, which directly affects the weight gained and consequently the honey production by the colony.

The influence of pollen on the susceptibility of honey-bee larvae to Bacillus larvae☆☆☆

Abstract Pollen, water, or nothing was added to the food of worker honey-bee, Apis mellifera, larvae aged 6–18 hr. Six hr later larvae from each of these three groups received, in their food, either Bacillus larvae spores in water, or water only. Pooled data from seven replicates of this procedure show that spore feeding preceded by pollen feeding resulted in a 71.17% mortality; spore feeding preceded by water feeding resulted in 94.84% mortality; and spore feeding preceded by nonexperimental feeding resulted in 92.75% mortality. Mortality in groups not receiving spores was below 11.00% in all cases. Chi-square analyses showed a highly significant reduction in mortality associated with pollen feeding.

Behaviour Genetics of Nest Cleaning in Honeybees. VI. Interactions of Age and Genotype of Bees, and Nectar Flow

SummaryTwo genetic lines of bees were used to study removal from the nest of brood killed by cyanide. The Brown line, resistant to American foul brood, removes dead brood promptly, and is called hygienic. The Van Scoy line is susceptible to American foul brood, removes dead brood very slowly, and is called non-hygienic. Control colonies having both young and old bees from a single line responded to dead brood as expected: Browns were fast removers and Van Scoys were slow, regardless of the presence or absence of a nectar flow. Likewise “mixed” colonies, having foragers (old bees) of the Van Scoy line and hive bees (young bees) of the Brown line, quickly removed cyanide-killed individuals from the brood nest under both dearth and nectar-flow conditions. Mixed colonies with foragers of the Brown line and hive bees of the Van Scoy line removed cyanide-killed individuals from the brood nest very slowly in the absence of a nectar flow, but much more rapidly during a flow. Both young and old Brown bees concentr...

Length of life and Dry Weight of Worker Honeybees Reared in Colonies with Different Worker-Larva Ratios

SummarySmall colonies consisting of a caged queen and young adult workers, ranging in number from 200 to 2800, were given 400 eggs to rear. Positive correlations were found between the numbers of workers and the adult life-span and dry weight of worker progeny they reared. Dry weight and life-span were also positively correlated. It is suggested that a nutritional factor is involved. Syrup, pollen and water were provided in a flight cage.

Defensive Behaviour and Production of Alarm Pheromone in Honeybees

SummaryWorker bees of an “aggressive” line (Brown) were more easily alerted to disturbance, and much more responsive to alarm substance, than those of a “gentle” line (Van Scoy). The sting apparatus of Brown workers contained about one-third more isopentyl acetate (IPA) than that of Van Scoy workers. Brown x Van Scoy hybrids responded to human breath and to measured amounts of IPA to the same extent as Van Scoy, leading to the conclusion that the gentle Van Scoy response is due to dominant heredity. Response of the hybrids to disturbance (removing the hive cover) was intermediate, indicating lack of dominance. Production of IPA in the hybrids was very variable, but on the average it resembled that in the Brown, and gave an indication of heterosis.

Selection for resistance and susceptibility to hairless-black syndrome in the honeybee

Abstract A two-way selection experiment for resistance and susceptibility to hairless-black syndrome, a probable viral disease in the honeybee, was carried out for four generations. From the parental generation of 15 colonies (reared from three basic stock colonies) tested for disease resistance, one-fifth were selected to start a resistant line and one-fifth to start a susceptible one. Thereafter these two groups were kept genetically separate and, from each tested generation, an average of about 22% of the best colonies were used as parents of the next generation. Bacteria-free inoculum, which was fed to challenge these bees, was prepared by macerating and centrifuging specific numbers of bees showing symptoms of hairless-black syndrome and collected from a number of colonies in our apiaries. Resistant and susceptible lines did not differ significantly in the first selected generation. In the second, third, and fourth generations, the two lines diverged increasingly, and in each generation, they differed statistically at the 1% level of probability.

Behaviour Genetics of Nest Cleaning in Honeybees V. Effect of Previous Experience and Composition of Mixed Colonies on Response to Disease-Killed Brood

SUMMARYMixed honeybee colonies were established of approximately equal numbers of two genetic lines of workers, one which removes brood killed by A.F.B, from the brood nest quickly (hygienic type), the other slowly (non-hygienic). The mixed colonies removed diseased-killed brood as quickly as colonies composed entirely of the hygienic genotype. When the two genotypes of bees in the mixed colonies were separated, their subsequent behaviour was the same as that of the pure-line controls. Learning by association with bees of another type did not affect their hygienic behaviour. In small colonies in which about 13% of the bees were of the hygienic type, the dead brood was not all removed.

Successful Selection of Honeybees for Fast and Slow Hoarding of Sugar Syrup in the Laboratory

SummaryFive generations of two-way selection for hoarding behaviour by young, caged bees in the laboratory resulted in a fast and a slow line. In the fifth generation of selection, worker bees from the colonies of the fast line took an average of 5 days to collect 20 ml of sugar syrup from a vial, whereas workers from colonies of the slow line required slightly over 14 days. The colonies of the second, fourth and fifth generations of the selected lines were tested for weight gains in the field. Fast-line colonies of the second generation gained more weight than slow-line colonies in three field tests. Fast and slow colonies of the fourth and fifth generations showed similar weight gains. Some possible explanations for this lack of consistent superiority of the fast line are presented.

Behaviour Associated with Hairless-Black Syndrome of Adult Honeybees

SummaryPatterns of adult honeybee behaviour associated with the disease named hairless-black syndrome are described. Bees that were apparently healthy vigorously chewed with their mandibles at the bodies of diseased bees inside the hive and at the hive entrance, thus rendering them hairless and shiny-black in appearance. Individually marked bees engaging in these chewing attacks sometimes licked the thorax of diseased trembling bees. Bees subjected to chewing attacks usually remained passive, sometimes offering food or stroking their probocis, and rarely tried to escape. Attacking behaviour apparently occupied some bees fully for a part of their lives. The level of attacking behaviour in observation hives was cyclic, with a peak every 4–12 days, and a daily peak between 12.00 h and 16.00 h. The behaviour patterns of attacking and attacked bees differed from those of cleaning and cleaned bees. Attacking behaviour was also unlike that of guard bees attacking robbers; however, it was similar in nearly every ...