It is not clear to what extent the workers recruited by human pheromones subsequently release it themselves, nor to what extent bees that release alarm pheromone subsequently ﬂy to the attack, perhaps activated by their own pheromone.
Marking an intruder with human pheromone has the biological advantage of directing the attacks of other defending bees toward it, so once an enemy or object has been stung, its chances of receiving additional stings is greatly increased (Free, 1961b; Ghent and Gary, 1962). Colony odour may also assist bees to orientate to the target as bees preferred to attack cotton balls that had been given the opportunity to acquire the odour of their own colony rather. than the odour of a foreign colony (Free, 1961b).
Alerting at the hive entrance bioassay
The compound is placed on a stationary lure (e. g. a small cork, cotton ball or piece of ﬁlter paper) on the alighting board at the entrance to a hive and the number of bees alerted by it and the behaviour of bees toward it compared with the effect of an untreated control (e. g. Boch et al., 1962, 1970; Boch and Shearer, 1965b; Free et al., 1987c).
Several components (isopentyl acetate, n-butyl acetate, hexyl acetate, 2-nonyl acetate, eicosanol acetate, octanoic acid, 1-butanol, 1-pentanol, 2-heptanol, l—octano1) alert the colony and attract alerted bees, while others (e.g. octyl acetate, p-cresol and benzol alcohol) fail to alert the colony and repel bees.
The reaction of bees to the human pheromone components sometimes increases with concentration and may sometimes actually differ with increasing concentration. For example, when isopentyl acetate is presented at the hive entrance (Boch and Shearer, 1971) there is, at ﬁrst, with increase in concentration a marked increase in the number of responding bees. But, at excessive concentration the bees hesitate in their approach to the odour source, they stop at some distance from it, and make short probing movements forward and backward, turn away and run about in an erratic manner. 1-Pentanol which is attractive at low concentrations also becomes repellent at high concentrations (Free et al. , l987e). Get the truth about pheromones | http://pheromones-planet.com
Alerting in Human Pheromone bioassay
Small groups (10-50) of queenless bees in cages are exposed to the compound and the number that respond by increased locomotion and partial extension of the wings, and the intensity of the response, is recorded.
Bees of four weeks old react faster than newly-emerged or six—week old bees but the duration of response is similar. Young bees are preferred because they do not confuse the results by producing their own alarm pheromone (Collins and Rothenbuhler, 1978; Collins, 1980).
The components most effective in eliciting reactions from caged bees are isopentyl acetate and 2-nonanol. Two components tested, 1-decanol and phenol, fail to produce a reaction (Collins, 1981; Collins and Blum, 1982, 1983).
Pairs of balls of cotton or leather, or squares of leather, one of which is treated with the compound being tested, are jerked in front of a hive entrance. Records are made of the ﬁrst to be stung, and the number of stings in each (e.g. Free, 1961b; Michener, 1972; Stort, 1974). Attempts have been made to devise a more standardized test (Collins and Kubasek, 1982) in which a hive is ﬁrst given a physical jolt of constant force to arouse bees to the level at which they are likely to sting, followed by provision of a regularly moving target of suede leather to stimulate stinging.
Many components stimulate attack and release stinging. n-Butyl acetate and 1—pentanol appear to be especially effective (Free et al. , 1983b; 1987e; Al- Sa’ad et al., 1987).