The test was whether a mosquito would associate blood with DEET, and therefore prefer to bite people wearing DEET.

…the scientists fed the insects warm blood for 20 seconds, releasing DEET during the last 10 seconds.

That part was repeated three times before the mosquitoes were exposed to solely the scent of the repellent.

This time, more than 60% of the insects tried to bite the fabric — even though there was no blood.

Then, one of the scientists offered up their hands — one clean, the other coated with DEET — to the trained mosquitoes to see which one they would bite.

The result was beyond doubt: the insects preferred the hand covered in repellent.

Now the the question is how and at what point an association would be made, not to mention why DEET isn’t a true repellent.