Today’s wildlife contribution is another absorbing photo-themed story by Athayde Tonhasca Junior. His tale is indented, and you can enlarge the photos by clicking on them.
According to the Woke canon, practically every scourge of humanity – poverty, colonialism, inequality, racism, global warming – is the work of prostate-bearing people, particularly the white variety. But Homo sapiens is not alone: the European honey bee (Apis mellifera) and the wool carder bee (Anthidium manicatum) have also been indicted for the sin of male toxicity.
As bad raps go, the one earned by honey bee males (drones) is hard to beat. Known as freeloading loafers whose single purpose in life is to copulate, they have been tagged with the unflattering ‘flying sperm’, and called ‘lazy Willies’ by the Germans. Even Shakespeare vilified ‘The lazy yawning drone’ (Henry V).
But the Bard and others were too quick to judge.
Researchers have not given male bees much attention because of their reputation as secondary players. But we do know that drones are fundamental for the workings of a bee colony by producing body heat that helps maintain the temperature of the hive. Honey bees do not overwinter, so thermogenesis (heat production) is a life or death matter for the colony. Because drones are bigger and stronger than female workers, their contribution is disproportionately higher.
Whatever input drones may have in the functioning of a colony, all are dramatically and fatally surpassed when they reach sexual maturity. On a warm and sunny day during the mating season, drones fly out to meet their mates from the neighbourhood 10 to 40 m above ground. These clouds of bachelor bees can be thousands strong. After all available males have gathered, virgin queens leave their hives and join in: love is in the air.
Fig. 1. A honey bee drone © Waugsberg, Wikimedia Commons.
Thanks to its big eyes, a drone spots a queen in the melee, zeroes in and grabs her. Mating is completed in less than five seconds, during which the drone’s endophallus (a penis equivalent) is turned inside out into the queen and inflated by haemolymph (‘blood’) under high pressure. As haemolymph rushes into his endophallus, the drone loses control of his body and falls back, unable to move. Ejaculation happens at such speed and force that it can be heard by people as a popping sound.
Alas, these amorous exertions cannot end well for the lucky suitor. His endophallus breaks off, leaving its extremity inside the queen. The drone drops to the ground and dies shortly after. You can watch a dramatization of the event in this video:.
Fig. 2. A honey bee’s everted endophallus © Michael L. Smith, Wikipedia Commons.
However, his anatomical sacrifice does not guarantee sole paternity. Another drone may remove the piece of endophallus from the queen and mate with her, and the process may be repeated with up to 20 successive drones.
Fig. 3. Semen being collected from a drone for a honey bee germplasm collection © USDA.
Life has more misfortune in store for our drones. They have a grandfather and grandsons, but not a father or sons. Such surreal family settings come about because of haplodiploidy. This tongue-twister refers to a reproductive system where females have two sets of chromosomes (just like us), but males have only one. After mating, a queen bee stores sperm in an internal sac called spermatheca. She may release some of the sperm when an egg passes down her oviduct, in which case the egg is fertilized and generates a female with two sets of chromosomes. If no sperm is released from the spermatheca, the egg will produce a male with a single set of chromosomes inherited from the queen: there is no genetic input from daddy. Sex is determined in a similar way for all Hymenoptera (bees, ants, and wasps), Thysanoptera (thrips) and a few other insects.
The consequences of haplodiploidy are profound. Human offspring share 50% of their genes with their mothers and 50% with their fathers, so siblings share on average 50% of their genetic material: (50% + 50%)/2. Female honey bees however share 50% of their mother’s genes, but all of their father’s. So they are related by (50%+100%)/2, which is 75%. You can find a detailed explanation of these calculations here. [JAC: this assumes that the female is inseminated only once.]
This 75% helps solve Darwin’s ‘one special difficulty’ which he stumbled upon when writing On the Origin of Species. Almost all bees, ants and wasps in a colony are sterile workers whose function is to gather food, protect the nest and help the queen lay eggs; they do not reproduce therefore are not subject to natural selection. How could these social insects evolve?
The answer to Darwin’s conundrum is kin selection: because sister bees are more related to each other than they are to the queen or any possible daughters, they have a better chance to pass on their genes by helping their mother produce more sisters, rather than by reproducing themselves. The theory of kin selection involves self-sacrificial behaviour and altruism, and because it is supposed to be applicable to us, naturally it has been controversial and debated for years.
While these drone shenanigans take place in an apiary, in a garden nearby a bumble bee wavers lazily over a patch of lamb’s ear (Stachys byzantina), as if considering whether its flowers are worth a visit. Before the bee makes up its mind, out of nowhere a black and yellow projectile collides mightily against it. The stunned bee falters and dips in the air, and is hit again. Struggling to stay aloft, it turns around and flees as fast as its battered wings allow it. If the poor bee could glance back, it would spot the aggressor now turning its attention to an unsuspecting honey bee.
The bumble bee and honey bee had the misfortune of invading wool carder bee territory. Males of this species are notoriously aggressive towards perceived threats, either other males or any bee that may have an eye for plants from which female wool carder bees collect pollen, nectar or nesting materials.
Fig. 4. A male wool carder bee © Bruce Marlin, Wikipedia Commons.
Male wool carder bees are all ruthless determination. Witnesses have reported five bees knocked down in quick succession, bumble bees and honey bees with their wings torn apart, victims thrown to the ground and mauled by bites and strikes from the attacker’s abdominal spines. Two males have been observed hovering face to face like stags readying for battle. When they clashed, the smaller bee fell to the ground, wings outstretched and abdomen vibrating (presumably dying or limping away afterwards).
Fig. 5. Details of a male’s menacing abdominal spines © Soebe, Wikipedia Commons.
Such Rambo-like aggressiveness has biological causes: polyandry and a physiological quirk known as ‘last male sperm precedence’. Polyandry – from the Greek for ‘many husbands’ – describes when a female mates with several males in a breeding season. This mating system is uncommon among bees; for most species, females copulate once with a single male. But wool carder bees are polyandrous, just like honey bees: monogamy is not an option. Last male sperm precedence happens when the male copulating last in a sequence of partners has a better chance of fertilising the female. So to assure paternity, a male must fend off potential competitors and do as much mating as possible with any female in his territory: as often as every six minutes. This short film follows the exploits of a male wool carder bee (warning: contains scenes of sex and violence).
But for the female, life is not all harassment from an aggressive Lothario: thanks to her guardian, she has a patch of pollen and nectar all for herself, free of competitors. She can focus on feeding and building her nest, which celebrated naturalist and entomologist Jean-Henri Fabre (1823-1915) considered ‘quite the most elegant specimen of entomological nest building’. She begins by stripping the fuzz from the leaves and stems of lamb’s ear and related plants such as mint, deadnettle and sage (family Lamiaceae). This material is rolled into a ball – watch her do it – an operation akin to ‘carding’, the process of separating wool threads for the production of cloth:
Fig. 6. A carding machine. Wikiwand.
Fig. 7. A female wool carder bee collecting nesting material from lamb’s ear © Ilona Loser, Wikipedia Commons.
The female will carry this bundle to a pre-selected cavity such as a hole in dead wood, a crevice in the mortar joints of a wall, or a hollowed plant stem. Once inside the nest, she will shape the collected fibres into a cell in which she will lay an egg and deposit a mass of nectar and pollen to provide for the larva. She will build several cells in a single cavity, then seal up the entrance.
Fig. 8. Rendition of a wool carder bee life stages. From left to right: pupa, larva, egg, and adult (female). © Samantha Gallagher, University of Florida Featured Creatures.
This bee has a Palearctic origin (Europe, Asia and North Africa), but was accidentally introduced to north-western USA is 1963. From there, it has dispersed throughout the country and the Americas all the way to Uruguay. It is spreading in Britain too: once confined to southern England, it was recorded in Edinburgh in 2011.