Posted on: 02 March, 2017
Author: Alexander P
The presence of a brood incubation pheromone has recently been demonstrated (Heinrich, 1973). This does not appear to originate from the brood but is deposited on it. The immature stages of a bumblebe... The presence of a brood incubation pheromone has recently been demonstrated (Heinrich, 1973). This does not appear to originate from the brood but is deposited on it. The immature stages of a bumblebee colony are incubated by the adult bees for long periods each day which help maintain them at a relatively high temperature. This incubatory behaviour appears to be re- leased by an odour the queen herself gives to the site when she lays eggs. The incubation pheromone also seems to guide the queen over short distances to the brood clump in the darkness of the nest, and on approaching the brood clump she palpates it with her antennae before incubating. Queens do not discriminate between incubation sites they have marked themselves and those marked by other queens of her own species. However, Heinrich (1973) found that queens of the two species he was observing (B. vosnesenskii and B. edwardsii) did not incubate brood marked by queens of the other species. When workers are present in the nest they probably also read and respond to the message but this has yet to be demonstrated; perhaps they reinforce it. Sometimes it is possible to induce workers to rear brood of a bumblebee species other than their own, resulting in colonies populated with workers of more than one species. It would be interesting to see whether workers in such colonies learn to respond to the brood marking pheromone of the other species present. The brood marking pheromone appears to be relatively involatile; sites and brood clumps marked by the queen remain attractive for several days after the brood has been removed. Probably a signal from the eggs initially releases brood marking behaviour, perhaps as they are laid. But the actual presence of brood is not always necessary for an incubation site to be marked as queens held in captivity sometimes incubate particular spots on the oor of their cages before they have laid any eggs. The site at which this incubatory pheromone is produced remains to be discovered. A first step would be to mark articially potential incubation sites with extracts from different parts of the queen’s body and see which release responses. Pheromones produced by bumblebee brood probably stimulate foraging (page 75) so it is quite possible that a pheromone from the brood itself may contribute towards the signal to incubate. No tests have been made of the relative attractiveness of two brood clumps from one of which the brood has been removed according to http://worstthing.org/what-is-a-human-pheromone/ Trail pheromone at the nest Nests of bumblebees are often located at the end of underground tunnels, in the midst of matted vegetation, or among an accumulation of rocks. It is likely that returning foragers would use the odour of the nest to help guide them to it, but bees leaving to forage must have some means of nding their way from the nest to the nest entrance. When bumblebee colonies, housed in nest boxes, are given clean, glass entrance tunnels the bees initially hesitate before using them, and do not readily pass along them until they have been well used, and presumably have acquired the odour of the nest or the bees. Cederberg (1977) demonstrated that B. terrestris workers both lay and follow odour trails between the nest and nest entrance. The bees were at rst restricted to using a narrow path across a sheet of paper placed between nest and nest entrance. They were then given access to the whole sheet of paper but nearly all kept to the trail already established, even when it was angled at a different direction to the original. Presumably, as for honeybees (page 110), the trail pheromone is deposited by the feet and tip of the abdomen. Source: Free Articles from ArticlesFactory.com Alexander P is a blogger from Los Angeles who studies pheromones.