A living prehistoric relic, the scorpion fly is a permanent guest at the ugly-bug ball, says Ian Morton.
There are beautiful insects and insects handsome to the human eye, but among the least pretty of those six-limbed legions is one directly descended from ancestors that flourished in the Permian period, some 250 million years ago. It is a living fossil plainly deserving of survival, for botanists surmise that, before the emergence of bees and other busy insects, its forebears were essential pollinators of early seed-bearing plants.
With diminutive measurements — it is barely half an inch long, with little more than a 1in wingspan — in magnification, the scorpion fly looks like something out of the creative depths of science fiction. It perches high on its legs in the stance of a parked Concorde, below its prominent brown compound eyes droops a large beak and between the long, black-blotched lacy wings is a yellow-and-black body culminating in the feature that gives it its name: a plump, scorpion-like tail the colour of a cockroach, which can curve menacingly upwards and forwards. It is by no means a handsome fellow.
So much for appearances: the scorpion fly is a harmless little critter, after all. The arching tail is sported only by the male, has no sting and carries a pair of claspers for mating — in fact, it is his genitalia, which he presents to a female after giving her a ball of saliva and mashed insect to gain approval. The beak has a tubular sucking mouth and will draw in pollen, nectar and fruit juice. Tiny jaws deal mainly with dead insects, although live aphids may be taken. The scorpion fly is prone to pilfering victims trapped in spiders’ webs and any spider that intervenes may also be eaten. It does not fear entanglement in the web, because it can dissolve the silk.
Found in woodland edges, hedge bottoms and among brambles and nettles, three species of scorpion fly are present in the UK and were named by Linnaeus in his 1758 classifications. The most common, Panorpa communis, and the more thinly distributed P. cognata and P. germanica are widespread in England and Wales, but do not reach Scotland. Members of the Mecoptera order, they are unrelated to the creature whose common name they share. In appearance, their closest relative in this country is the tiny snow flea Boreus hyemalis.
A hunting male Scorpion Fly, Panorpa communis, perching on a leaf.
Scorpion flies spend most of their time crawling around vegetation, but may take to the air in short, whirring straight-line flights and are quick to remove themselves if disturbed. They are active from May to September, breeding in midsummer in moist leaf litter. A male emits a pheromone to attract a mate and performs a little dance with flashing wings when she appears. The female deposits one generation of eggs in the soil per season — usually a clutch of 10 or so. Once hatched, the caterpillar-like larvae graze on decayed organic matter and insect remains, before pupating over winter.
Scorpion flies: The facts
- Scorpion flies have been found useful in forensics. Being among the first to arrive at a cadaver, their presence helps to determine how recently death occurred
- In the US, which hosts 60 species, entomologists regard scorpion flies as good models for the study of insect mating behaviour. It has been discovered that some males imitate females in order to steal other males’ food. Such behaviour has not been reported in this country
- Scorpion flies are among the fearsome insect combatants to have been commandeered by the video-game industry. In more bad publicity, Stephen King deployed them among the nightmarish assailants trapping people inside a supermarket in his 1980 novella The Mist. The author’s flies were 2ft long, the pinkish colour of burned flesh that had repaired, had bulbous eyes on short limber stalks and they clung to the window glass with fat suction pads
- The word ‘scorpion’ appeared in Middle English some time about the end of the 12th century, deriving from classical mythology and astronomy via Old French
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