ABSTRACT
Chemical communication has reached an advanced and sophisticated form in social insects. These are endowed with exocrine glands which produce an array of compounds, such that almost every facet of their social behavior is mediated by pheromones. There is very little information available concerning the function of mandibular gland secretion in solitary bees. The labial glands constitute two pairs of glands, one in the head and one in the thorax, that are intermittently developed in the bees. In male bumble bees the glands of the head are especially developed and fill most of the head cavity. In bumble bees, Dufour's gland secretion is possibly used to mark trails extending from the center of the nest to the outside. The chemical diversity expressed in Dufour's gland of bees and its function in the bees' biology may be used for chemosystematics. Dufour's gland composition in bumble bees seems to be highly diverse in comparison to the other bee families.
