Sociologists love to study social insects (bees, wasps, ants, termites, etc) because they provide a chance to study altruism in society driven entirely by evolution. The quirks of honey bee sex are such that, on average, a worker shares more genetic material with her queen-mother's (female) children than with her own (male) children. Previously, the hive altruistic structure was thought to be held together mainly by the workers' self interest in propagating (on average) as much of their own genetic material as possible.
Some new work <A href="http://www.sciencenews.org/articles/20050319/bob8.asp">suggests a certain amount of jealousy-driven force is also necessary</a> to keep society orderly.
Bees practice <a href="http://www.bumblebee.org/Haplodiploidy.htm">haplodiploid</a> reproduction. Females carry two sets of chromosomes, while males carry only a single set. Thus, every sister receives one of two sets of chromosomes (half her genome) from her mother and one set of chromosomes from her father. Thus, there is a 50% chance that any worker shares %50 of her genetics (the maternal half) with her sister. The paternal half of their genetics will be identical, so haplodiploid sisters are share on average (0.25+0.5) 75% genetic material.
In the article linked above, researchers induced workers to lay a number of unfertilized eggs by isolating the workers from the queen. The unfertilized eggs were marked and placed in a normal portion of the same hive, where they were quickly destroyed by the other workers.
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In honeybees, as in wasps and ants, workers don't mate but can develop working ovaries and lay eggs. Their unfertilized eggs hatch and grow, but only into males.
The females in these species, the vast sisterhood that does the work of the colony, come only from eggs laid by the queen. These eggs get fertilized with sperm that the queen stores when she's young. In honeybees, that youthful bout often involves 10 males. All workers are therefore sisters or half-sisters.
Occasionally, the honeybee queen also releases an unfertilized egg. It grows into a royal son. Ratnieks pointed out that a royal son is more closely related to the average female honeybee worker -- he's her brother or half-brother -- than the son of some other worker would be. Thus, for the best chance of spreading her own genes to the next generation, the worker honeybee should favor her brother and kill the other workers' sons. From her point of view, the less-related male just drains colony resources without much genetic payoff.
But what if the queen mated with one male only? That might change everything, Ratnieks predicted. Given that males come from unfertilized eggs, a worker of a singly mated queen would on average share more genes with a nephew -- the son of one of her sisters -- than with a brother. Workers of the saxon wasp, Dolichovespula saxonica, for example, tend not to police their coworker's eggs if the queen mates once, but tend to do so if the queen has multiple mates, Ratnieks and his colleague Kevin Foster reported in 2000.
Relatedness isn't the whole story, however. Last year, another lab's survey of policing reports from a broad range of species highlighted ones with singly mated queens that don't conform to the simple relatedness model Ratnieks argues that the survey doesn't disprove his original model; it had predicted that such factors as colony efficiency might change the incentives for policing. For example, a worker that starts laying eggs often stops working.
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[Ratnieks] Wenseleers, and their colleagues in Brazil are examining Brazilian bees of the genus Schwarziana. ... The Schwarziana royalty arises in two sizes in the presence of a reigning queen. When a full-size queen matures, workers encircle her and quickly build a dome-shaped prison of wax around her. They regularly feed her by biting a little hole in the wax and passing through food. They then seal the hole. Such a spare queen remains under control.
On the other hand, what Wenseleers calls the dwarf queens challenge the status quo of the colony. They're the same size as workers and emerge from the same kind of cells, yet they have well-developed ovaries. Unchecked, they could mate and take over colony reproduction. These little queens don't get wax boudoirs. Instead, workers typically kill them.
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To see policing in detail, the researchers put several new queens into an established colony. In four cases, a single worker caught a queen and neatly bit off her head in as little as 4 seconds. Sometimes, five or so workers grabbed a young queen's legs, antennae, and mandibles and dragged her around the colony for perhaps an hour, gradually pulling her apart.
One queen lay immobile, as if feigning death, for 14 hours, and thus outlived all others of her kind. However, when she finally moved, she acted aggressively toward the workers and the rightful queen, and the workers killed her too.
All that drama sounds as if the interests of an individual insect aren't necessarily the same as those of her colony, even though she and the other members are all closely related. The Brazilian dwarf queens and the Yucatán queen free-for-all offer routes to the throne—if they weren't blocked by swift police action.
Wenseleers argues that, overall, "coercion plays a more important role than kinship in favoring cooperation in insect societies."
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