"Bees can distinguish between ordinary odorant molecules and versions with some hydrogen atoms replaced by deuterium, because the two variants of the smell-triggering molecules elicit different patterns of neural encoding in their brains. Thats the conclusion of a team of scientists in Italy, who have sought to clarify the debate over whether bees can discriminate isotopic forms or isotopomers of odorants. ..."
Read more here: Royal Society of Chemistry