PEST CONTROL PEST OF THE MONTH — DRAIN FLIES Hairy drain fly a summer nuisance
‘Adult
drain flies have short, hairy bodies and wings which give them a distinctive hairy or fluffy moth-like
’ appearance.
It is the time of the year when fly populations are on the increase. Some flies find themselves unintentionally trapped inside our houses, especially on warm days. Eagerly attempting to escape, they become trapped on the inside of windows. There are other flies which are more mysterious, whereby overnight, populations suddenly appear, and no-one seems to know where they have arisen from.
An example of such an insect is the ‘drain fly’ (Telmatoscopus albipunctatus) — a tiny fly that has been recently turning up in bathrooms all over the region. It resembles a very small moth and for this reason, it is commonly referred to as a bag moth, or moth fly. Similarly, this drain fly is also often mistaken for a garden whitefly.
As the name (drain fly) suggests, these insects live in plumbing pipes and shower or sink drains. Even though they inhabit ‘unhygienic’ environments, they do not pose any threat to human health. Instead, the adult drain flies are more of a nuisance factor. This is because once they emerge from the drains, they congregate in large numbers around light sources, illuminated display lights, windows and window sills located near the drain(s). As a result, they are often found in large numbers, seemingly attached to bathroom walls and ceilings.
Adult drain flies have short, hairy bodies and wings which give them a distinctive hairy or fluffy moth-like appearance. The fly has a lifespan of approximately 20 days and is capable of laying 35-100 eggs. The eggs are laid just above a waterline around a shower or sink drain, where a build-up of grease, hair and/or glutinous sludge exists. When the eggs are splashed with water, hatching begins within a couple of days and worm-like larvae appear. The larvae are almost transparent, making them hard to see but they are extremely robust and tough. Larvae feed for a few weeks before pupating. As you can imagine, these larvae must possess a hardiness to enable them to reside in such a risky environment that includes hot water, household bleaches, soaps and cleaning products as well as other waste that is flushed down the kitchen or shower drain. However, very fine water-repelling hairs over their tiny bodies provide adequate layers of protection.
What is the relationship between drain flies and drains? It is simply that the larvae feed off bacteria found in the drains. Consider the amount of waste deposited in household drains. It all contributes to a build-up of glutinous sludge or grime on the inner surface of the drain. Bacteria begins to accumulate, thus providing the perfect food source for the growing drain fly larvae.
Killing the adult flies is often ineffective because more flies emerge from the larvae living in the drains. The answer to controlling their numbers lies in reducing the larval food source. Therefore, any waste sludge must be completely removed. Mechanical cleaning of the drains remains the most effective control method, however, sometimes this is an impracticable feat. Therefore, the injection of an antibacterial foam (or enzymes) capable of breaking down (or digesting) the sludge or grime deposits is a far more simple, easy and effective solution.
■ Brent Page is a Horowhenua Entomologist and Director of Nature’s Way Pest Control. For more information, visit www.nwpc.co.nz/pests/flies