CODEX Entry 9200: Bees
Remarkably little is known about the lifespan of solitary bees, of which there are 300 species. This is partly because they generally live underground. Estimates are that the females have long development periods of upto a year, and live actively for a year after that, only flying outside in spring and summer, for a lifespan of about 2 years.
By contrast, hive based insects, eusocial species of ants, bees, wasps, and termites, manifest vampirism, extreme examples of a small non-working elite living upto 100x longer than the other members of the colony, that are worked to death. This occurs despite the elite and the workers sharing the same DNA. Social insect queens, and in some cases kings, live longer than reproductive adults of comparable non-social insects, despite sustaining very high rates of reproduction. Longevity and reproduction typically are negatively correlated. Social termite and ant queens are the only animals known that can live for decades while also producing thousands of offspring per day.
Drone honey bees (males), as larvae, receive worker jelly for just 2 days at which time they are started on a diet of honey. Male bees technically have only a mother, and no father, coming from unfertilized eggs, and can’t feed themselves, dependent on the female workers even as adults. Only a few hundred are created each spring, compared to upto 50,000 females in the hive at any one time. The drones live just 3 weeks as adults. They have unusually large eyes, a heavy body structure, and must fly fast, all to attract the queen. Their average flight time is thus only 20 minutes. They will fly to a drone congregation area, from several different hives, and attempt to impress a queen. Should he succeed in mating, all of the drone’s blood rushes to his penis, which causes him to lose control over his body, which falls away, leaving his penis attached to the queen. He dies soon after. If he fails to mate, the drone is ejected from the hive at the end of the summer season to die of cold or starvation.
Worker (females) lifespans vary depending on the season, 27 days in the summer and 175 days in the winter. Workers spend their first week cleaning brood cells. Cells are inspected by the queen, and if unsatisfactory, must be cleaned again and again. They feed the young males drones who can’t feed themselves, and give worker jelly to the worker larvae.
The better nursing bees will be selected to feed royal jelly, glycoprotein royalactin, to queen larvae, inducing the queen phenotype by activating the Epidermal Growth Factor Receptor (EGFR). They nourish the larvae by glandular secretions of their mandibular, hypopharyngeal, postcerebral and thoracic glands. In combination the royal jelly and glandular secretions affect which genes are turned on and off via DNA methylation. MicroRNAs, complementary to DNA methylation, determine whether the larvae become a queen or worker.
Other young workers, at one week old, become the queen’s attendants, feeding and grooming her, including cleaning her anus. More importantly, they are fed the queen’s mandibular pheromone (QMP) and in turn they spread this throughout the hive. Chemically, QMP is very diverse, with at least 17 major components. It appears to serve several different functions, and research to date has not been able to isolate the effect of each one. In 2002, research confirmed that, while 29 of 250 worker bees had fully developed ovaries in a control group, only 1 of 250 worker bees, exposed to QMP, had developed ovaries. In this manner the queen is able to suppress fertility in other worker bees.
At two weeks old workers move to tougher work, wax production, building, sealing and repairing cells. They are required to exude wax from four sets of glands in their abdomen. Other work includes managing the store of nectar and pollen, packing it into cells, adding a small amount of honey so that it will not spoil. The walls of the hive are also covered with a thin coating of propolis, a plant resin, which, in combination with added enzymes and mud, has antibacterial and antifungal properties. Dead bees and failed larvae must also be carried some distance from the hive by mortuary bees. Some worker bees have to collect water while others, including drones, fan the hive, cooling it with the evaporating water. Guard bees stand at the front of the hive entrance, defending it from any invaders such as wasps.
After two weeks, in the summer, workers now transit to foraging and scouting, travelling up to 3 kilometres away for nectar, pollen, or propolis. Some bees remain on at the hive as the queen’s ‘police’, watching for any egg laying by worker bees. The lifespan of summer worker bees is very short, 1/7th of winter bees, not because of weather, but because of the suicidal workload demanded by the queen. Their lifespan naturally increases to 175 days, even in the summer, if they are placed in a colony that doesn’t have a queen.
Queens are raised in specially constructed queen cells, and take the shortest time to develop, 16 days. Virgin queens will quickly find and kill, by stinging, any other virgin queen or unemerged queens in their cells. All the while they are piping, a loud battle cry, an intermittent vibration on the note G#. Queens live, as adults, two to eight years. Queens become sexually mature 6 days after emergence and then take two or three mating flights per day. On average, they mate with 17 drones in this early period, and then store all six million sperm needed to fertilize eggs for the remaining years of their lifespan. With the exception of these early mating flights the queen does not leave the hive again until swarming, when the colony splits.
The queen is now laying her body weight in eggs each day, around 2,000. As this continues the hive will eventually have to split. The old queen leaves with the prime swarm before the first virgin queen emerges from a queen cell. If the queen is not producing enough eggs to support the hive, the workers create a queen larvae and kill the reigning queen by clustering tightly around her and raising her body temperature, causing her to overheat and die.
Only the queen produces fertile eggs, but unfertilized eggs can also be laid by worker bees if they choose to activate their ovaries. These unfertilized eggs develop into drones (male bees). Queen-destined larvae produce high levels of juvenile hormone (JH), which prevents ovarian apoptosis (suicide) in the 5th-stage queen larvae. JH levels also activate the transcription of genes and insulin signaling that create a queen, and the production of chemical fertility cues, QMP, present on the females’ cuticles.
In honey bees, differences in workers and queens can be found in several age-associated factors, including hormones, nutrition, immune senescence, and oxidative stress. Weyer, in 1927, while working with ants, was the first to recognize that queens perform ovisorption. This is where the queen reabsorbs the fertilized eggs into her body. As the queen ages the percentage of her own fertilized eggs that she ‘reabsorbs’ increases. Signiphora, a small wasp, has an extremely rapid rate of egg development and resorption, taking just two hours. Queen bees also eat the unfertilized eggs produced by worker bees. Fat body trophocytes, vitellogenic cells and oocytes are rich sources of nutrition acquired in this manner, which allow the queen to produce vitellogenin (Vg). Vg is high in the abdomen in the young queen, but increases with age in the head and thorax. Old queens show much higher Vg expression than young queens, while worker bees have much lower levels than queens. Vg reduces oxidative stress in honey bees by scavenging free radicals that can lead to aging or illness. Not surprisingly, queens are more resistant to oxidative stress than workers. Similarly, the gut microbiota of worker bees show clear signs of aging, gradually accruing Proteobacteria associated with inflammation and imbalance, and becoming depleted of healthy Lactobacillus and Bifidobacterium. In contrast, queens maintain youthful cellular function with a very different microbial succession in the gut.
Workers “police” each other, killing eggs laid by workers or confronting egg-laying workers. Worker policing is a behavior seen in colonies of all social hymenopterans (ants, bees, and wasps). Worker policing ensures that the offspring of the queen will predominate in the group. The workers or the queen also act aggressively towards fertile workers. The dwarf honey bee workers all have activated ovaries and are capable of laying eggs, but worker policing ensures that none of them reach maturity. With the Asiatic honey bee, when queens are removed, up to 40% of the workers activate their ovaries. However, policing workers continue to eat the worker-laid eggs. Worker policing appears to ensure the queen and her attendants’ ability to live a long life of inactivity. In rare cases, worker-laid eggs carry mimicked queen hydrocarbons and escape policing, a condition known as the anarchic syndrome.
Termite queens can live 50 years and kings 20 years. Workers or soldiers live 1 to 2 years, broadly similar to some ant species. An inhibitory pheromone is produced by the queen to prevent the development of female secondary reproductives. This substance is circulated through the colony by immature termites that routinely consume the feces of nestmates. A colony of about 1,000 workers created in two years can multiply into 300,000 workers in five more years.The queen, king and alates, termite swarmers that will set up new colonies further afield, are considered the primary reproductives in a colony. In some cases, the queen allows secondary or tertiary sub-queens to also produce offspring. They do not have wings.
Dracula ants, so named because they suck the blood of their young in a process of ‘nondestructive cannibalism’. The queens in larger colonies feed exclusively on the ‘blood’ of their own larvae. Even when other food is available, larval haemolymph is their only food. The queens gently stroke then pick up a larva, carefully piercing its skin with the tips of their jaws and sucking the drop of haemolymph that bleeds out. Female Paussus beetles will lay eggs that hatch into sweet-smelling ant larvae, exuding an irresistible bouquet of ant attractants. Ants approach, only to be punctured and sucked dry by the ravenous, vampiric larvae.