Swotting up

Tuesday 30 July 2019

As flies become more prevalent in the summer months it's interesting to know that not all flies are created equal before you get swotting.

The group of insects are known as the Diptera - and an expert from La Societe Guernesiaise has talked us through the different fly types and what they get up to in your home or garden.

Anecdotal comments shared with Express over a number of weeks have suggested the number of flies in local homes has increased this year. La Societe Entomological Section Secretary Trevor Bourgaise said that making that distinction would be difficult but that either way flies do not pose as much of a hygiene hazard as people think. 

"I personally have not noticed unusually large numbers of flies but like all insects there are more about in warm weather. There are roughly 120,000 species in the world and Guernsey at a guess probably has between 500 and 1000 species.

"The flies that will most concern people are things like blow flies, bluebottles and other house flies. They will be attracted to food left uncovered to lay their eggs.  Dung flies are attracted to droppings of farm animals and generally as a rule do not enter houses, in fact they feed on smaller flies themselves. 

Pictured: A dung fly up-close. 

"There are still many species on Guernsey awaiting  discovery. Most people if asked about flies would immediately think of the house flies, bluebottles, blow flies etc but in actual fact very few flies cause a problem for man. They are at the bottom of the food chain and thus represents an important food source for other creatures.

"There are various groups in the Diptera one such group are the hoverflies, this group includes the Hornet Mimic Volucella zonaria, hoverflies act as pollinators and their larvae eat aphids. Thus they are a gardeners friend.

Pictured: Hornet Mimic Volucella zonaria.

"Some groups are very attractive and the Trembling Wing flies are very well marked, Bee Flies as the name suggests resemble bees and two species can be seen including the beautiful species Villa modesta which breeds in sand dunes and can be found on Herm.They lay their eggs to feed on the larvae of other insects.

"St Mark's Fly Bibio marci is a species that will have been seen by everyone, it emerges around St Mark's Day 25 April and is instantly recognisable as it flies with its legs dangling. It is a very common species. Many species of fly larvae mine the leaves of plants and in other instances create galls. Many species are restricted to one type of plant," he said.  

Pictured above: A fly trap.