in social insects and act to maintain colony homeostasis. A releaser pheromone has a weaker effect and influences behavior only. Most worker bees utilize releaser pheromones for various hive functions including alarm and aggression, sex attraction, trail marking and recognition (Free 1987; Slessor et al. 2005). Importantly, pheromone communication within a honey bee colony is shaped by the complexity, synergy, context and dose of each signal and conveyed via both temporal and spatial distribution throughout the hive (Slessor et al. 2005).
Figure 4.3 Life inside a honey bee hive is complex with many work activities, behaviors and functions occurring among the various worker, drone, and queen bees. Such social living demands effective communication for survival. Many of the hive activities and the ability of a colony to adapt to changing conditions are shaped by the chemical language of honey bees; pheromones may elicit behavioral or developmental changes among bees to maintain colony homeostasis and guide these hive functions.
Source: © Lauren D. Sawchyn, DVM, CMI. Chapter: Physiology of the honey bee, authored by Rolfe M Radcliffe and illustrated by Lauren D. Sawchyn.
Queen Pheromones
The honey bee queen largely regulates colony activities, producing a variety of pheromones, known collectively as the queen signal, to support many hive functions such as cleaning, brood rearing, comb‐building, guarding, and foraging (Free 1987; Slessor et al. 2005; Bortolotti and Costa 2014). Such pheromones also influence drone mating, swarm clustering and the queen retinue behavior, while also suppressing worker bee ovary function and egg laying, queen supersedure, and limiting the potential for queen rearing (Figure 4.4). When the queen is removed from a colony or dies, her absence is discovered with little delay and the colony swiftly initiates queen rearing because of the loss of queen pheromones (Free 1987; Slessor et al. 2005; Bortolotti and Costa 2014). After an extended time without a queen, the colony's worker bees stop completing their hive tasks, begin laying unfertilized eggs that mature into drone bees, and the colony declines toward collapse.
Queen mandibular pheromone, previously believed only secreted from the mandibular gland, has been most studied and is comprised of many different chemical compounds affecting many of the aforementioned hive behaviors (Free 1987; Slessor et al. 2005; Bortolotti and Costa 2014). Queen mandibular pheromone is now recognized as queen retinue pheromone because of its multiglandular origin (Slessor et al. 2005). This multicomponent queen pheromone attracts a continually shifting cohort of 6–10 young worker bees that feed and groom the queen (Free 1987). These young bees form the queen's retinue who, in addition to caring for the queen, collect and distribute her pheromones about the colony via antennal contacts and trophallaxis (Slessor et al. 2005; Jarriault and Mercer 2012). Queen retinue pheromone has many stimulatory properties beyond shaping the queen's court or retinue, including formation and steadiness of the swarm cluster, attracting drone bees and mating, influencing worker tasks and development, comb building, brood rearing, as well as foraging behavior. In addition, this queen pheromone is vital for the regulation of colony reproduction and worker physiology, inducing worker sterility when the structure of the hive – having a productive, fertile queen – favors the long‐term genetic interests of the worker bees (Slessor et al. 2005; Princen et al. 2019).
Figure 4.4 A colony of honey bees survives in large part because of the presence of a healthy queen. The queen honey bee produces several pheromones, known collectively as the queen signal, helping to regulate colony activities. Such pheromones support many important worker bee hive functions including cleaning, comb building, brood rearing, foraging behavior, and hive defense. Further, the queen signal is necessary for drone bee attraction and mating, maintaining the swarm cluster and queen retinue behaviors, as well as inhibiting worker bee reproduction and egg laying, queen supersedure, and queen rearing.
Source: © Lauren D. Sawchyn, DVM, CMI. Chapter: Physiology of the honey bee, authored by Rolfe M. Radcliffe and illustrated by Lauren D. Sawchyn.
Significant queen signal redundancy has been identified throughout the pheromone communication repertoire of the honey bee colony (Slessor et al. 2005; Princen et al. 2019). Besides the queen mandibular gland, other sources of the queen signal have been isolated from the tergal, labial, tarsal, Dufour's, and Koschevnikov glands (Slessor et al. 2005; Bortolotti and Costa 2014). Located beneath the abdominal tergites and more developed in the queen, the tergal glands secrete pheromones that support the function of the queen retinue pheromone. The tarsal glands, present in all three bee castes, release a footprint pheromone that in the queen inhibits queen cell construction by the worker bees (Bortolotti and Costa 2014). The Dufour's gland, closely associated with the sting apparatus in the female honey bee, is another part of the queen signal and also provides worker bees with information about queen fertility and reproductive potential (Dor et al. 2005; Bortolotti and Costa 2014). The Koschevnikov gland, located near the sting shaft of females, is yet another source of queen signal, and with gland degeneration beginning at one year of age contributes to the failing of aging queens (Bortolotti and Costa 2014).
Worker Pheromones
Worker honey bees also make use of a variety of pheromones, and most glands in both the queen and worker honey bees are fully developed yet secrete different pheromones (Free 1987; Ritter 2014; Bortolotti and Costa 2014). Further, gland maturity in worker bees follows a temporal pattern that parallels the changing tasks and activities of the worker bee within the colony. Worker bees employ several pheromones during their lifetime including alarm, Nasonov, footprint, and forager signals to help in colony defense, for orientation and marking sites, and for identifying the colony (Bortolotti and Costa 2014; Ritter 2014). Worker mandibular pheromone is also produced when needed in queenless colonies to suppress ovarian development in other workers when egg‐laying workers or psuedoqueens emerge (Bortolotti and Costa 2014).
The defense behavior of a honey bee colony is well known and alarm pheromones released from worker bees help guide this response (Bortolotti and Costa 2014; Free 1987; Breed et al. 2004). Defensive behavior tasks occur prior to foraging in worker bees and two types of behaviors are recognized: guarding and defending (Breed et al. 2004). Guard bees watch and monitor the hive entrance, inspect all who wish to enter, and reject non‐nestmates; soldier bees fly out in the face of danger, and chase, bite, or sting intruders. Honey bees are able to recognize nestmates of the same colony or non‐nestmates of other colonies through chemical signals present in the lipid covering of the insect cuticle. Both the sting apparatus, including the Koschevnikov gland, as well as the mandibular gland produce pheromones that evoke defensive behavior through the recruitment and amplification of other worker bees (Bortolotti and Costa 2014).
Worker honey bees produce a pheromone from the Nasonov gland that is restricted only to this caste (Bortolotti and Costa 2014; Free 1987). The gland secretion is composed of several volatile compounds that function to attract other bees, and is released during three main contexts: during swarm clustering, marking their hive entrance, and marking of water and foraging sources (Bortolotti and Costa 2014; Free 1987). The worker footprint pheromone, secreted from the tarsal glands of worker honey bees, may share the role of marking the hive entrance
