Nick Baker’s hidden Britain
The parasite that lives in mining bees
If you want to find an animal that is odd with a host of strange adaptations and a convoluted and complex lifestyle to match, then you can’t go far wrong with a parasite. Parasites are masters of subterfuge that have evolved highly specialised tricks and adaptations to outwit their hosts. The parasite known as Stylops melittae takes this weirdness to a whole new level.
Stylops belongs to a group of insects called the twisted wings, or Strepsiptera, of which there are about 17 species in the UK – all just as weird as each other. But what exactly are they? These furtive members of our fauna are so odd that science hasn’t yet fully committed to their description. One thing is for sure: they are insects.
The minuscule male – only a few millimetres long – has enough recognisable insect traits to be convincing – six legs, three body sections, antennae and compound eyes.
The same cannot be said of the female, who lives her entire life inside another insect: a mining bee. She never leaves her bee host and, as a consequence of this, has done away with legs, wings and eyes altogether, and barely has a mouth or antennae. She is, in effect, just a big bag of eggs. The only part of her that is visible ( just!) is her head and the top of her body, which poke out between the segments of her host bee’s abdomen. It is visible as an odd, scale-like protrusion, and gives little away of the sac-like abdomen that fills the back end of the bee. While she doesn’t seem to do much other than hijack the bee’s body and absorb all the nutrients she needs, she’s not entirely lazy in love. She helps the male out by emitting a pheromone from her brood canal
– an orifice that opens in the back of her neck. This potent perfume brings him in fizzing. The only obvious issue is how he does his business – especially since she doesn’t have any genitals...
It turns out, as if things aren’t bizarre enough already, that her internal arrangement isn’t standard either and neither is their very brief (a matter of seconds) love life. Stylops go in for the somewhat kinky act of traumatic insemination. The male is armed with a kind of penis/tin-opener hybrid, which is stabbed into the female’s neck. He pumps his sperm into her body cavity through the wound. Here, it fertilises the eggs that are free-floating around in her bloodstream.
The weirdness, however, is not yet over and the life-cycle takes an even more gruesome turn. The fertilised eggs, between 4,000 and 7,000 of them, drift though her bloodstream and hatch into larvae that effectively eat her from the inside out. When matricide is complete, they escape from the canal in the back of her neck. Remember, this is all going on inside a bee. Their goal now is to get off the ride and into a flower, to then transfer to another bee.
The larva’s hairy body, grippy legs and adhesive organs all help in the process of hanging onto the new bee’s body. When a suitable host has been latched onto, they produce a substance that weakens its cuticle, softening it enough to gain access. Then they crawl inside and start to grow and mature, ready to start the process all over again – males emerging through the bee’s body, the females staying put.