Fifty years ago, bed bugs were nearly eliminated in the United States by using of pesticides like DDT. Today bed bugs are back in beds and theaters. DDT is no longer used due to environmental issues. Pyrethrums are currently the top choice for bed bug infestations. Pyrethrums are especially useful to us because they generally have a stronger effect on bugs than on humans and animals.
Bed bugs have become resistant to even this chemical pesticide. What happened that allowed the bug population to increase?
A) the chemicals used currently are weaker
B) the chemicals no longer can penetrate bed bugs brains
C) the bed bugs of today are exactly the same as the bed bugs of fifty years ago
D) the bed bugs that survived the DDT years ago, reproduced new generations of chemical resistant offspring