Insects are sturdy creatures, hatching in great numbers, with some species producing as many as thirty generations in one year.
比較一般生物，昆蟲不但生命力旺盛，而且繁殖迅速，短短的一年裡面可能就有卅世代，基因改變迅速，農藥很快就對它失靈；人類不斷加重藥劑、發明新藥，結果蟲子的抗藥性卻有增無減。