[aruanan]

How Bedbugs Are Becoming Resistant to Today's Insecticides (How did Genes KNOW about Insecticides?)

They don't know. In any wild population, there is a wide range of genetic variation. Some individuals of a species are more susceptible to certain toxins than others. Kill those off and the others that are inherently more resistant will survive and replace those with lower resistance. There are other responses to environmental threats that result in increased rates of mutations caused by portions of genes getting swapped around leading to different physiological responses to the cause of stress, some of which ensure survival.

[aruanan]

See spontaneous transposon mutagenesis resistance.