Don't dismiss flies

If you ignore the cold and rather wet weather that greeted the Bank Holiday weekend, it would be fair to say we have had a rather pleasant spring with some unseasonable warmth. This period of warmth drew out a whole range of insects, from holly blue butterflies and scurrying ground beetles to industrious bumblebees. Various species of fly have also been on the wing, some of which have tended to enter the house and terrorise one of our two dogs. The dog in question, an eight-year old springer spaniel, was stung by a wasp when she was a puppy. Since then, she has taken a dislike to anything that flies around emitting a buzzing sound; you can always tell when there is a fly in the house by the way in which the dog looks nervously over her shoulder.

It is very easy to just dismiss these flies as all being the same but there are actually a great many different species, all showing slightly different lifestyles. For example, while some species lay eggs, others give birth to live young, a process known as viviparism. When we tend to think of flies we often have in mind the bluebottle, famously punned by the Goon Show, but there are many others with which we share our houses and gardens. Something of the revulsion that many direct towards the bluebottle can be seen in its Latin name ‘Calliphora vomitoria’, a reference to our fears that it can spread disease. Since the female bluebottle will enter houses and seek out exposed fish and meat for egg-laying (having done the same outside on decaying flesh or excrement) it is easy to determine the pathway by which a disease might reach us. The male bluebottle has more pleasant habits, and is more likely to be seen visiting flowers, particularly umbellifers, for nectar.

Another fly that is often seen in our houses is the common house-fly (Musca domestica). This species has proved its adaptability by establishing itself across the globe, living alongside Man and laying its eggs in our rubbish and excrement. Amazingly, the 900 or so eggs that each female lays can hatch within eight or nine hours, the whole life cycle being completed in as little as two weeks. Equally familiar is the greenbottle, one of a number of very similar looking flies with a blue-green or emerald-green colouration. This particular species is very variable in size, the result of how nutrient-rich is the medium in which it hatched. Unlike the bluebottle and house-fly, the greenbottle rarely ventures into houses, preferring instead to forage and reproduce outside. So, next time that you see a fly, don’t just dismiss it.