How to rear genetically modified flies
20 November 2013 Last updated at 10:00 GMT
A UK biotechnology company has applied for permission to carry out the first field trial in Europe of a genetically modified insect.
If it receives approval, the company, Oxitec, will carry out a small-scale test of GM olive flies in Spain.
The aim is to combat this olive crop pest by releasing male flies that have a "female-killing gene". If the GM flies can outbreed the wild flies, the female offspring will die - reducing the olive fly population.
Here, scientist Martha Koukidou from Oxitec explains how the company rears the GM flies to prepare for Spanish trials.
Video journalist: Victoria Gill