S1: One of the most dangerous insect pests is the locust.
P: At first they look just like ordinary grasshoppers, which are harmless and unable to fly very far.
Q: Until about thirty years ago, no one knew where locusts came from or why they appeared in the different countries they attacked.
R: Then they change in appearance and develop wings which enable them to fly long distance.
S: Then it was discovered that there are two stages in the life of locusts.
S6: At this stage, they gather in huge numbers and rise from the ground on theri powerful wings in cloud.
The Proper sequence should be: