May is the season of white. Cow parsley and hawthorn revel in it, dressing every roadside. Horse chestnuts put up great candelabras of elaborate off-white blossoms. Wild garlic also chooses white, and its underrated blooms can produce as startling a drift of colour on a woodland floor as bluebells do, if not in such an original shade. In Whiteknights Park ramsons are generally scarce, but there’s an incredible swathe in the small wooded area on the north side of campus. Perhaps the densest patch of all is in the fringes of the Catholic chaplaincy garden, from where it finds its way into many a summer term soup lunch. It’s almost as though it grows here by design, a plant that is both beautiful and delicious: clearly this is a holy place.
Besides hungry students and staff, there’s a small beast that is even fonder of eating wild garlic. I love niche-specific species like this and the targeted searches their choosiness facilitates, so once I became aware of the connection I resolved to determine whether or not it occurred in Reading. I started by setting four traps, nestled within the garlic patch and surrounding by developing flower shoots. None caught the animal I was looking for, but whilst collecting them I finally saw it. At least, I think I did. A squat, dark hoverfly with square grey markings on its abdomen. Ponderous for a hover, it slowly descended to a flower about 15 inches from my left hand. With my right hand I made to grab either hand-net or camera, but the second of indecision over which I should pick up first was all the time the fly needed to vanish.
The fly I saw met the description of the one I was searching for, which goes by the name Portevinia maculata. Nonetheless, without a photo or a specimen I couldn’t prove to anybody that it was anything more than a figment of my sun-baked imagination, and despite extensive searching the following day no further individuals were found. The fly is and remains a Whiteknights Park enigma, a fantastic beast that in a Schrödinger-esque sort of way may – or may not – be out there even now, resting among the ramsons. As wildlife mysteries go it’s not exactly the Lord God Bird, not even the Lord God fly; plenty of rarer and objectively more striking hoverflies are out there. But it does add a satisfying kind of depth to an otherwise anonymous, overlooked corner of campus.
Hoverfly expert Steven Falk’s excellent Flickr album illustrates what I was looking for. He describes Portevinia maculata as “a widespread but localised fly, often present at good stands of the food-plant in woods but sometimes absent for reasons that are unclear”. Sounds about right!