No flies on these autumn-loving larvae
Swarms of black cluster flies have been besieging homes around the North Island as they take advantage of perfect hatching conditions.
Kirsty McIntyre Campbell said the window sills and kitchen floor of her rural property near Masterton were black with flies by the end of the day.
‘‘If I’m home, I vacuum at least three times a day. They are doing my head in.’’
Sandra Potts, of Auckland, said her house had been badly affected during the past two weeks.
‘‘It works best to spray them at night on the ceiling, just a small amount, and then vacuum about 20 minutes later.’’
Protekt Wairarapa pest and hygiene services owner Bill Ousey said he had taken a lot of calls about cluster flies in the past week.
‘‘The weather has been just right for them. In the past, I’ve been to houses that have had masses of them in the roof, and unoccupied houses where they literally covered the floor.’’
Ministry of Primary Industries entomologist Alan Flynn said the flies could hatch in large numbers when conditions were right – a spell of wet weather that was then followed by sunshine.
The flies’ larvae grew by parasitising earthworms brought out of the ground by damp conditions. The flies lay their eggs in grass and, when the larvae hatched, they burrowed down to find a worm to parasitise.
When autumn began to cool, they looked for a place to hibernate, which was why they suddenly appeared in large numbers in houses, Flynn said.
‘‘In the next month or so as it gets colder they could well increase, but the thing to remember is that, even though there is a certain yuck factor to them, they are not a food pest and won’t lay eggs on your food.
‘‘They are really just looking for a warm place to escape the cold.’’
Massey University entomologist Maria Minor said the better the soil, the better the conditions for the larvae.
‘‘Typically they thrive in areas with good farmland, because of the plentiful supply of host earthworms.’’