Profitable Wonders James Le Fanu
No one has ever had a good word for those two domestic blood-sucking insects – the louse and the bedbug. The former, to the dismay of parents, has a particular affinity for their children’s hair to which they superglue their shiny white eggs. The toxic effects of their saliva injected several times a day when feeding causes the weariness and irritability of feeling ‘lousy’. The reddish brown bedbug is more irksome still: crawling out of the furniture at night it torments its victims, stabbing viciously at their exposed flesh, leaving in its wake a shudder-inducing dark trail of blood and worse across the sheets.
The third type of domestic bloodsucker, the flea, tends to elicit more mixed feelings: the nuisance of their itchy pinprick bites offset by a grudging admiration for their exuberant athleticism. Their jumping prowess, too rapid for the eye to follow, the equivalent in human terms of clearing the dome of St Paul’s, ranks among the marvels of the natural world.
The naturalist Pliny wrote appreciatively of their ‘skipping merrily’ in the victualling houses of Ancient Rome. And when magnified fifty-fold in Robert Hooke’s Micrographia of 1665, the revelation of their streamlined elegance was the first intimation of the intricate anatomical detail of even the humblest form of life. ‘But as for the beauty of it’, Hooke commended to his readers, ‘the polish’d suit of armour, neatly joined’; the serrated lancets ‘by which this busie little creature pierces the skin’ and ‘the curious contrivance of its legs … for asserting that strength, such as no other creature’.
And, though unknown to Hooke, the male’s (minuscule) penis has the distinction of being ‘the most elaborate genital organ in the animal kingdom’, claimed Dame Miriam Rothschild in an article in the journal Scientific American describing her lifelong fascination with these ‘jolliest of creatures’. Her father, Charles, head of the British branch of the banking dynasty, assembled the world’s largest collection – 20,000 slides and bottled specimens – of the 1,500 known specimens, a third of which he had described himself.
After his death Dame Miriam, without any formal education or scientific training, undertook the formidable task of cataloguing the collection, eventually published by the British Museum in six hefty volumes. Her subsequent, and unique, contribution to flea studies are recorded in a further (astonishing) 300 scientific papers.
She turned her attention first to the mechanism behind that prodigious leap, a necessary adaptation for a wingless insect moving from one host to another but whose range (at 100 times its body length) and frequency (up to 600 times an hour) eclipses that of any other animal.
The opportunity to visualise the flea in action with a specially devised camera running at 3,500 frames per second showed it first crouching downwards and then somersaulting into the air performing several cartwheels before landing the right way up – the fine bristles on its outstretched legs functioning as grappling irons on the host’s hair. The power generated by the contraction of those limb muscles is not nearly sufficient to account for that jumping prowess but resides rather in a small elastic ball in its thigh joint – ‘a nearly perfect rubber, yielding 97 per cent of stored energy when released’. The practicalities require a complex anatomical arrangement of tendons to squeeze the elastic within the joint, which is then held in that compressed state by two spicules of bone or ‘catches’ until they are released – launching the flea upwards with an acceleration equivalent to that of a satellite re-entering the earth’s atmosphere.
The major challenge to the flea’s parasitic lifestyle is in finding the host that will provide it with a limitless supply of food (in the form of blood) for free. Dame Miriam’s further investigation of the lifecycle of the rabbit flea demonstrates just how ingenious this can be. Put simply, when the rabbit becomes pregnant the hormonal changes in its blood prompt its resident population of female fleas to start producing eggs. Once the baby rabbits are born, both male and female fleas jump ship and the blood of the new young hosts initiates their mating ritual.
The male’s elaborate genital organ composed of two penile rods uncurls like a watch spring, the thicker of the rods guiding the thinner (‘like a rope running over a pulley’) to deposit its sperm and fertilise her (now mature) eggs. These are duly laid over the next few days to undergo the process of metamorphosis into cocooned larvae from which the fleas’ offspring emerge to begin their blood-sucking existence. Meanwhile, the parent fleas, having colonised the next generation of rabbits, return to the mother to repeat the cycle when next she becomes pregnant. There is, of course, much more concerning these jolliest of creatures to merit the admiration bestowed upon them and the patronage of those distinguished and diligent Rothschilds.