The Test Conditions

I live next to a park and a canal. Every year I go on holiday in August and return to a small house infestation of flies.

The test flies

I can only comment on fruit flies (also known as Mediterranean fruit flies, or Medfly). I cannot comment on the common house fly or any other flying creature. Fruit flies are the really small flies, kind of more wing than body, slow moving and keen to live somewhere that isn't kept scrupulously clean (like if you have been away on holiday), or live somewhere close to heavy vegetation.

The Environment.
I live next to a park and a canal - a nice environment for fruit flies. They annually invade my kitchen in August. I do not like to spray pesticides (flyspray) in my kitchen where it may get onto surfaces and crockery. I therefore wanted an alternative to pesticides.

The test
A 2 foot strip of flypaper was hung in my kitchen.
At the same time, this blue light insect killer was switched on.

The Result
After after 4 days the kill rate was:
Flypaper - 57 flies
Vermatik fly killer - 24 flies

Economics
Fly paper can be bought for less than 50p a strip and has no running costs.
The Vermatik fly killer has purchase price of about £40 PLUS a daily consumption of 30 watts per hour for the light (plus more for the electrocution grid?)

Conclusion
Yes it works - but its hardly the total answer to the problem. I still have flies -its kill rate is slow. It is comparatively expensive to buy and has higher running costs than fly paper. It looks nicer than fly paper...but what the heck - if you have flies around, its as much a give-away as streamers of fly paper in your kitchen.