Wild Bedbugs become insecticide resistant because of the mutations and natural selections.
Explanation:
As the huge amount of pesticides and insecticides are sprayed in the rooms for cleaning, the pests and insects like bedbugs dies in huge portions because of the toxin. But some of the bedbugs remain alive as they have mutations that help them to detoxify the toxins given, or bypass the metabolic processes so that the toxins don't hamper them much.
Now as the population becomes very small(bottle neck effect), the nature selects these organisms over the other to propagate more sufficiently and enormously. As the nutrients and supplies are also available, so the bedbugs don't suffer any lack of nutrition which can be a determining factor of their population.
Thus the wild bedbugs become resistant to insecticides while the experimental one remain succeptible to insecticides.
