They’re some of the strangest and most reviled insects on the planet, but they’re also incredibly useful

WORDS SCOTT DUTFIELD

They’re a pest at a picnic, a bin’s best friend and an enemy of silence, but flies are also some of the best pollinators on the planet. The first ‘true flies’, of the order Diptera, flew onto the scene during the middle of the Triassic period around 247 million years ago. Today this order of insects encompasses more than 150,000 different species, including hoverflies, crane flies and mosquitoes, accounting for around 14 per cent of Earth’s insect diversity.

The life cycle of true flies generally consists of four stages: egg, larva, pupa and adult. For many flies, the journey to adulthood is short. Female houseflies (Musca domestica) can lay up to 500 eggs over a period of three or four days. Under the correct temperature conditions the eggs will hatch in just 20 hours, and larvae will emerge. After developing as a larva for between 4 and 13 days, the maggots pupate – their skin hardens and turns dark brown. While in the pupal stage, their legs and wings form, taking two to six days under optimal conditions, before they emerge as adults. Houseflies have at the very most two months to live, find a mate and reproduce to continue the cycle. The speed of their life cycle means that there can be as many as 20 generations of houseflies zipping around at the same time.