Best Pheromones Studies

Significant changes in worker bee physiology are related to queen pheromones. Gast (1967) found that the corpora allata undergo two growth phases, a first phase which is inhibited by 9-0-2 and a second phase in which development occurs only when a queen is present. Inhibition of oogenesis in workers has been reported by many researchers (e.g., Voogd, 1955; Butler 1957; Verheijen-Voogd 1959; Pain 1961; Velthuis 1970b, 1972) and has been demonstrated by confining worker bees in cages without queens or queen extracts. When such bees are properly nourished, the normally diminutive ovaries enlarge. In advanced stages, a few eggs may be produced. When “these workers are in colonies, some lay unfertilized eggs in worker cells. Apparently, the presence of the queen (and her pheromones) generally tends to inhibit female attributes related to reproduction, leading to a degree of regula- tion of worker bee activities which some authors interpret as a kind of ‘dominance’. Workers with enlarged ovaries apparently mimic queen pheromones to some degree. Velthuis et al. (1965) found that laying workers (advanced stage of oogenesis) and/or extracts of laying workers elicited retinue behavior and inhibited oogenesis in young workers under experimental conditions. Pain et al. (1967) did not detect 9-0-2 in laying workers.

Distribution of queen pheromones

The distribution of queen pheromones within the colony probably involves several mechanisms, one of which is clearly dissipation in the air currents within the hive. Butler (1954b, 1956) suggested that distribution is primarily by frequent food transfer between workers, in which ‘queen substance’ (9-O-2) is mechanically distributed, after being obtained initially by licking the queen’s body. The food transfer mechanism is theoretically possible. Nixon and Ribbands (1952) demonstrated that sugar syrup containing P32 rapidly was distributed to most workers within a few hours of feeding small quantities to a few workers in a colony. Loss of inhibitory effects (oogenesis and queen cell building) was observed when queen extracts were mixed with sugar syrup higher than 5—10%(Verheijen-Voogd 1959; Erp 1960; Pain 1961), although Butler (1956) and Butler and Gibbons (1958) did not detect any influence of sugar concentration on worker response. Johnston et al. (1965) fed radioactive 9-O-2 to workers in order to study the rate of metabolism and the nature of metabolites produced within the worker bee gut. They found that 9-O-2 was quickly metabolized to 9-ketodecanoic acid, 9-hy- droxydecanoic acid, and 9-hydroxydec-2-enoic acid, and suggested that the speed of conversion into these compounds was sufficiently rapid to account for the rapid onset of queenless behavior following the separation of the queen from the workers.

Consequently, transmission of pheromones in transferred food is possible, but the efflciency of this mechanism is very difficult to evaluate. Velthuis (1972) suggested that queen pheromones are more likely to be disseminated by those worker bees which contact the queen during retinue behavior. The pheromones ‘adhere’ to the other workers where the materials express effects through the mechanism of olfactory perception — primarily antennal. This mechanism was suggested earlier by Verheijen-Voogd (1959) who proposed that olfactory perception alone is sufficient to elicit worker responses. Further support for the olfactory perception mechanism was found by Erp (1960), Butler (1961), Butler and Fairey (1963), and others.

Butler, Callow, Greenway and Simpson (personal communication) followed the distribution of tritiated 9-0-2 applied to thoraces of isolated queens and workers.