We all have our weaknesses – two of mine are flies and books, so how could I resist finding a home for a copy of the attractively titled “British blood-sucking Flies” by Edwards, Oldroyd and Smart (1939) which was being discarded by my University Department? There were keys to each family, numerous line drawings, detailed species descriptions, two appendices and 42 colour plates. At the bottom of the last page, upside-down, is the signature of B.P. Marmion who was Professor of Bacteriology at Edinburgh University in the 1960s and 70s when I was a schoolboy. The Department of Bacteriology became that of Medical Microbiology which is where I worked for a spell, several Professors later. Coincidentally, he had previously been at the Pathology Department at Cambridge University where I did my PhD, at the Walter and Eliza Hall Institute in Melbourne, Australia where I did my first post-doctoral research, and one of his research interests was hepatitis B virus – while I worked on hepatitis C and hepatitis E virus.
This book has been sitting on my shelves for twenty years now, still little read, until today when I was able to use it to identify a fly brought to me by the chap who has the office above mine. Notably, we have been friends for 45 years since we met at school, both avid members of the school Natural History Society, the highlights of which were weekend expeditions to the country cottage of our Biology teacher, Mr Faithfull. In the photo I am wearing the green and yellow jacket and he is sitting below me to the left. For all those years we egged each other on in a series of semi-serious competitions – cross-country running, stone throwing for distance, accuracy and bounces, bird watching, living things in our gardens, moth trapping, moths without trapping and landing on Scottish islands.
The tiny fly in question is a member of the family Simulidae, commonly known as black flies, and notorious biters. The veins in their wings are distinctively stronger at the front edge, and the thorax looks huge and muscular compared to the tiny head tucked under at the front and the stumpy abdomen at the rear. This fly was biting my friend’s neighbour’s horses and is a female. Going through the rather sparse key (which happens to be for females only) in “British blood-sucking flies”, I conclude that it is Simulium variegatum rather than the typical horse-pest S. equinum or the more common S. ornatum. The chapter’s preliminary text on the family notes that attacks on humans are not usually serious, with few reports of fatalities, although in Africa they act as vectors for the parasitic worm Onchocerca which causes river blindness. My only encounter with them in numbers was in New Zealand where they are known as sandflies. Setting up camp by a river one evening I wondered why my hair was starting to feel damp and sticky. The flies approach silently, make an incision with their scissor-like mouthparts, and secrete an anti-coagulant to prevent the blood clotting while they lap it up from the wound – my hair was damp with blood, and I quickly retreated to the tent, no match for the fly, another weakness I am happy to admit to.