6.1. Introduction

The pheromonal system of the honey bee, Apis mellifera L. is complex and composed of several caste specific chemical signals mediating various colonial activities in an integrative manner. These caste specific signals are known to be produced by over 15 exocrine glands in workers and queens (Free, 1987; Blum, 1992). Pheromone production by these glands shows age, task and caste-based variations (Blum, 1992; Winston, 1987; Pankiw et al., 1998; Robinson and Huang, 1998), which suggest plasticity in pheromone biosynthesis. Such biosynthetic plasticity has been demonstrated for the mandibular glands (Plettner et al., 1996), Dufour's glands (Katzav-Gozansky et al., 1997; Martin and Jones, 2004) and may also be true for some of the other exocrine glands.

Regulation of the biosynthesis of these pheromones within glands is mediated by hormones. For instance juvenile hormone (JH) is known to regulate the activity of the mandibular and Koshevnikov glands (Robinson, 1985) while pheromone production in the Dufour glands is regulated by unidentified brain factors (Katzav-Gozansky et al., 2007). It is probable that pheromone biosynthesis in other exocrine glands are similarly regulated by various hormones. 

To study the mechanisms behind the control of pheromone production, it is important to isolate the gland of interest and evaluate its performance in vitro via manipulation with potential regulatory factors. This is especially crucial when studying organs of a social organism whose function is affected at any moment by multiple external cues followed by activation of internal cues. The in vitro isolation of the gland enables the separation of the target tissue from the impact of suspected factors on its performance both at the organismal and molecular levels. At the organismal level we consider pheromone production, whilst at the molecular level we refer to gene expression evaluation via genomic and proteomic tools. So far, proteomic tools (see the BEEBOOK paper on physiology and biochemistry methods (Hartfelder et al., 2013)) have been used in studies of mandibular glandular performance in vivo (Hasegawa et al., 2009; Malka et al., 2009). The effect of each factor, their interaction and regulation mechanisms can be delineated using classical pharmacological methods but also with innovative molecular tools (e.g. RNAi-RNA interference, see the BEEBOOK paper on molecular methods by Evans et al. (2013)) without the interference of any social factors.

The idea of isolating pheromone producing glands was first successfully explored studying the control mechanism of sex-pheromone production in female moths (Soroker and Rafaeli, 1987), and thereafter  to study  ant postpharyngeal gland secretion (Soroker and Hefetz, 2000) and to discover the source of the locust pheromone phenylacetonitrile (Seidelmann et al., 2003).  This approach has been used largely to study moth sex-pheromone production and control (Rafaeli, 2009). In the case of honey bee exocrine glands it has only been briefly explored to study pheromone production by Dufour's and Mandibular glands (Katzav-Gozansky et al., 2000 and Soroker and Katzav-Gozansky, unpublished data).