Type evolutionary event has occurred-population of anopheles | Quick Homework Help

A population of Anopheles mosquitoes reaches very high densities, and is subjected to aerial spraying by IDT. The following six years, the mosquitoes are not observed at all, but the population was sprayed “just in case”. An outbreak occurs sevem years later,however, and this time, the aerial spraying with IDT is much less effective. Laboratory tests indicate that these mosquitoes are resistant to IDT, avoiding surfaces coated with it. It also seems that they have a reduced growth rate and lower fertility than mosquitoes from previous years. Field ecologists report that virtually every predatory insect has been eliminated from the regions sprayed with IDT.

a. What type of evolutionary event has occurred here? What was the likely mechanism for the change in the mosquito population?
b. What recommendations would you make as a mosquito control strategy for the future.