Final answer:
Pesticide resistance develops in insect populations through microevolution, where genetic changes lead to the survival and reproduction of resistant insects. This is most expected in environments with extensive pesticide use, as seen historically with DDT resistance. The purple-legged insects' possible resistance to the Bt toxin is a current example.
Step-by-step explanation:
Pesticide resistance in insect populations is a concern for both agriculture and public health. Insect populations would be most expected to develop pesticide resistance in environments where pesticides are used extensively. This resistance occurs through a process known as microevolution, where genetic changes within the population result in the survival of individuals that are resistant to the pesticides. Over time, these resistant insects reproduce, passing on their resistant genes, leading to a population that is less affected by the pesticide.
In the case of the Bt toxin and the hypothesized purple-legged insects, the observation that these insects may be increasingly resistant supports the idea that microevolution is at work. The purple-legged insects that survive the application of the Bt toxin will pass on their resistant traits to their offspring, potentially leading to a new subpopulation that is largely unaffected by this pesticide.
Historically, the evolution of DDT resistance in certain insect populations has provided a classic example of pesticide resistance. The widespread use of DDT resulted in selective pressure on populations, where resistant individuals were more fit and thus more likely to survive and reproduce, ultimately leading to a population predominantly composed of DDT-resistant individuals.