Where did all the butterflies?

Butterfly populations have declined greatly in recent years. Perhaps you have noticed that there are far fewer butterflies in their neighborhood than before! In the past, there were so many butterflies that clouds of migrating butterflies could sink ships to fill the sails. Also, "blood rains" were caused by millions of butterflies emerging from their cocoons, each dropping down a red droplet.You can imagine how many butterflies for this rain would be needed!