Brood Pheromones
Brood phermone (BP) have been studied in some depth. This may be partially explained by the fact that varroa use this pheromone as a kairomone, it attracts the female varroa at just the right time for her to enter the cell and reproduce . When it is at its peak, just before sealing of the cell, the female varroa slips under the larva so that she can reproduce during the pupal stage of the honey bee development. If the agrochemical companies could find a way of overcoming this action they would make a fortune.

In the 1980s and 1990s research proved that honey bee brood is known to have many effects in the colony such as stimulating pollen collection, inhibiting the ovarian development of workers, stimulating warming behavior , affecting rate of protein synthesis of hypopharyngeal gland, and inducing the capping of mature larvae by workers.

BP is produced by the larval silk glands, which in the adult become the thoracic salivary glands. The silk glands have a more obvious function in producing the 'silk' necessary for the construction of their pupal cocoon. The different pheromone constituents vary with the age of the brood and with caste. This leads the nurse worker bees to respond appropriately.

It is essential for nurse bees to be able to identify the brood, and more precisely its sex, caste, and developmental stage. Nurse bees can also discriminate between healthy and diseased brood. These signals are both chemical and mechanical.

In 1983 triglycerol Glyceryl-1,2-dioleate-3-palmitate, (GDP) was identified in drone brood.

This was followed in 1990 by the further analysis which identified the 10 fatty acid esters: five methyl esters- palmitate, oleate, sterate, linoleate, and linolenate and the same five ethyl esters- palmitate, oleate, sterate, linoleate, and linolenate. These 10 compounds only were believed to make up the brood primer pheromone until 2009 (see below).

Confusingly these ten components alone or in combination can also show releaser effects on adult bees.

Inducment to cap larva- methyl linoleate, methyl linolenate, methyl oleate and methyl palmitate elements of BP only.

Inducment to feed larvae- methyl palmitate and ethyl oleate elements of BP required.

Acceptance of queen cup- methyl sterate

Inducement to feed royal jelly- methyl palmitate.

Colonies have also been engineered to be more concerned with brood production by the artificial provision of brood pheromone, Pankiw et al 2004.

Nurse bees tightly regulate larval growth by adjusting the larval feeding according to larval age, indicating that nurse bees use larval pheromones to regulate larval diet.

E-β-ocimene (EBO) was identified by Maisonnasse A et al, 2009. An article written by Maisonnasse describes the properties of this element of the brood pheromone as being a primer. The eβ pheromone of first to third instar larvae significantly suppressed ovary activation in worker bees compared to controls (QMP also has this effect). It did not affect hypopharangeal gland development. Ocimenes are said to have a pleasant smell and are anti-fungal.

EBO is a volatile monoterpene and can dissipate quickly. This is probably why it wasnt identified earlier. The earlier identified BP and EBO are chemically distinct larval pheromones, but they can both induce similar physiological and behavioral changes in nurse bees.

Because it is highly volatile it can quickly diffuse throughout the hive, thus removing the need for foragers to come in close physical contact with brood to effect their behavior. EBO is comprised of a single compound, which means that its effects are not dependent on a blend of multiple compounds to cause a behavioral effect. (Ma 2016)

In a paper produced in 2018 Alison McAfee et al examined hygenic behaviour in honey bees. . EBO and oleic acid are released from brood upon freeze killing. EBO normally signals begging for food but when mixed with oleic acid it has a synergistic effect triggering hygenic behaviour. In their research they postulated that the strong smelling EBO got the nurse bees' attention and the oleic acid is the death cue (it is a well extablished necromone in other arthropods).

It is believed that hygenic bees possess superior olfractory sensitivity.

Scientific Beekeeping
Chemical Communication in the Honey Bee Society.
Queen and young larval pheromones impact nursing and reproductive physiology of honey bee (Apis mellifera) workers Traynor et al 2014
E-β-Ocimene, a Volatile Brood Pheromone Involved in Social Regulation in the Honey Bee Colony . Maisonnaisse et al 2009
Primer effects of a brood pheromone on honeybee behavioural development
Le Conte et al 2000
Effects of Brood Pheromone Modulated Brood Rearing Behaviors on Honey Bee (Apis mellifera L.) Colony Growth. Sagili et al 2009
Pheromone-modulated behavioral suites influence colony growth in the honey bee (Apis mellifera).
Pankiw T et al 2004
Assessing the role of β-ocimene in regulating foraging behavior of the honey bee, Apis mellifera, Ma et al 2016
A death pheromone, oleic acid, triggers hygienic behavior in honey
bees (Apis mellifera L.) McAfee et al 2018