Stinging bees often grip an enemy with their mandibles and Free (l961b) suggested that while doing so they might deposit an alerting substance. Maschwitz (1964) found that at a hive entrance more bees examined the mandibular glands (Fig. 2.3) of worker honeybees squashed on ?lter paper.
Like honeybee workers the ovaries of bumblebee workers usually remain undeveloped, but as the season advances and the bumblebee colony becomes more populous some of the workers develop their ovaries and lay eggs. If the queen dies this happens earlier. Ovary development and egg laying is frequently associated with aggression (Free, 1955b; Free et al., 1969). Egg laying workers often jab or bite one another and are attacked by the queen if she is still present. A Bombus lapidarius queen tends to attack most frequently those of her workers with the most developed ovaries (Free et al. , 1969). The most dominant workers in a queenless Bombus pratorum colony tend to spend their time astride egg cells, in which they have probably laid eggs, and try to repel intruders; a dominant worker especially attacks those whose ovary development approaches its own (Free, 1955b). In these circumstances individual recognition seems to be linked with ovary development and so possibly with the amount of pheromone produced. Learn about Athena 10:13 Pheromones Perfume | Pheromones-Planet.com
It was thought that the actual behaviour of a queen bumblebee suppresses the ovary development of workers and prevents or greatly discourages them from building egg cells and laying eggs particularly during the early stages of colony growth. As a colony grows, the active dominating behaviour of the queen is no longer able to effectively keep all her large family under control (Free, 1955a; Free and Butler, 1959; van Honk et al., 1980). This very physical means of inhibition probably still holds true, but in addition the queens of at least some species are known to produce inhibitory pheromones (Roseler, 1977; Roseler and Roseler, 1978). It has been shown that in colonies of B. terrestris, a populous underground nesting species, queen pheromone normally hinders synthesis by the corpora allata of the worker juvenile hormone that is necessary to stimulate ovary development, although it is not completely suppressed and egg maturation proceeds, albeit very slowly. However, removal of the queen results in a high level of juvenile hormone synthesis and within ?ve days some of the workers in a queenless colony are able to lay eggs. The process whereby the pheromone presence is transferred into a speci?c signal inhibiting the activity of the corpora allata is yet to be elucidated, and the queen pheromone concerned has yet to be identi?ed.
The pheromone appears to be produced by the queen’s mandibular glands and the queen probably spreads it over her body while she grooms herself. Extracts of a B. terrestris queen’s mandibular glands and of her body surface have the same inhibitory effect as a living queen (Roseler et al., 1981). B. terrestris colonies headed by queens whose mandibular glands had been removed were less effective at inhibiting worker ovary development than normal queens (van Honk et al., 1980) but more effective than no queen (Pomeroy, 1981) suggesting that there is a second inhibitory source or else the mandibular gland pheromone had been incompletely removed.