The mosquitoes are genetically altered to need a particular chemical in order for their offspring to be non-sterile. (Tetracycline IIRC) Without tetracycline in their food, any offspring the have will be sterile. (I’m afraid I don’t know the details of how this works genetically, but there are probably papers in the literature.)<p>So the company can happily breed their mosquitoes to keep a stock, feeding them on feedstock that contains tetracycline &amp; then can take a portion of the breeding stock &amp; eliminate tetracycline from their diet - their sterile male offspring can then be released into the wild to mate with fertile wild female mosquitoes.<p>I’ve heard that one of their client labs had trouble generating sterile males using Oxitec’s protocol: they eventually discovered that the feedstock they were using came from factory farmed chickens which had large amounts of tetracycline in their diet (as an antibiotic it’s used to boost growth rates in factory farmed animals).<p>(A neighbour works for them, so if anyone has any really pressing questions I can probably ask :) )<p>Edit: There’s a review paper which looks like it might answer some of your technical questions here: <a href="http:&#x2F;&#x2F;longnow.org&#x2F;revive&#x2F;wp-content&#x2F;uploads&#x2F;2015&#x2F;02&#x2F;Alphey-AnnRevEnt-2014-genetic-control-of-mosquitoes-copy.pdf" rel="nofollow">http:&#x2F;&#x2F;longnow.org&#x2F;revive&#x2F;wp-content&#x2F;uploads&#x2F;2015&#x2F;02&#x2F;Alphey-...</a>