1. Insects against which DDT was at first very effective apparently become immune to it, some resisting such deadly chemicals as hydrocyanic acid.

처음에는 ‘디디티’가 곤충에 대하여 효과가 대단히 좋았는데, 지금은 곤충들이 거기에 면역성이 있으며, 어떤 곤충은 청산(青酸)과 같은 화학 약품도 이겨낸다.