Which is an example of the bottleneck effect? green beetles move to a new location and build a new colony there. green beetles survive as birds don't see them, whereas brown beetles get detected. insecticide spraying eliminates all but a few of the beetles on an island.

A bottleneck is very narrow, which means that only a portion of the contents of the bottle cat get out (at the time). 

From this effect, people use the word bottleneck when only a few individuals of a population survive: 

the answer is: Insecticide spraying eliminates all but a few of the beetles on an island.

4, two dominant and two recessive