Final answer:
The decrease in pesticide resistance among insects suggests changes in pest management, use of different pesticides, or ecological dynamics have diminished the prevalence of resistant individuals, potentially also aided by effective biological control methods.
Step-by-step explanation:
When insects no longer are resistant to certain pesticides, it can be concluded that the pesticide resistance that had developed in those insect populations has diminished. The development of resistance is an example of microevolution, where through natural selection, the most resistant individuals survive and reproduce, spreading their resistant genes. However, the observed decrease in resistance suggests either a change in pesticide use, pest management strategies, or ecological factors that may have reduced the presence of resistant individuals or promoted the prevalence of non-resistant ones. Furthermore, ecologists have found that biological control methods can be effective at managing pest populations and delaying or reversing the development of resistance, while also avoiding environmental damage and protecting human health.