"Unnatural selection" fly lure-trap

This idea exploits behaviour selection and the fact that insects have short generational spans.

Flies are attracted to food sources, on which they often lay eggs, largely by odour. When they arrive at the food source, they then investigate by touch and taste.

The system requires the distribution throughout populated areas of scented lure traps.

These traps have a slowly-moving strip of material, textured to resemble an insect food source. They emit a synthetic odour of decay; alternatively, under the strip is located a suitable portion of decaying material which will attract flies, behind a fine mesh which does not allow the flies access to it.

The flies land on the strip, attracted by the smell. Thus reassured, they lay their eggs on the strip and depart.

The strip then passes under an intense ultraviolet source which sterilises the eggs.

However, there is a cunning twist.

The lure-trap also emits a synthetic smell, uniquely designed to be detectable (though not necessarily attractive) to insects at low concentrations, but very difficult for humans to detect. This odour must not resemble anything in the natural environment.

Flies which lay eggs in the presence of this smell will have a lower chance of successful reproduction. Flies that avoid the "signature" smell will have a better chance.

Over time - a relatively short time - flies will evolve that actively avoid the signature smell despite the presence of an attractive food odour.

All that is neccesary is to keep the lure-traps running in urban areas to maintain the selection pressure.