=Economic Importance of Grasshoppers.=--Great injury is often done to vegetation by grasshoppers; however, the millions of tiny but ravenous eaters hatched in early spring are usually soon thinned out by the birds. The migratory locusts constitute a plague when they appear, and they have done so since ancient times. The Rocky Mountain locusts flying eastward have darkened the sky, and where they settled to the earth ate almost every green thing. In 1874-5 they produced almost a famine in Kansas, Nebraska, and other Western states. The young hatched away from the mountains were not healthy, and died prematurely, and their devastations came to an end. Of course the migrations may occur again. Packard calculates that the farmers of the West lost $200,000,000 because of their ravages in 1874-5. [Illustration: FIG. 120.--FRONT LEG OF MOLE CRICKET. × 3.] The _cockroaches_ (Fig. 116), =kindred of the grasshoppers=, are household pests that have migrated almost everywhere that ships go. The _praying mantis_ (Fig. 117), or _devil’s horse_, also belongs to this order. It is beneficial, since it destroys other insects. Which of its legs are specialized? The _walking stick_ (Fig. 121) and _cricket_ (Fig. 118), like most members of the order, are vegetarian. [Illustration: FIG. 121.--FOUR WALKING STICK INSECTS.] Are grasshoppers more common in fields and meadows, or in wooded places? How many different colors have you seen on grasshoppers? Which colors are most common? Grasshoppers are very scarce in Europe as they love dry, warm countries. Why do locusts migrate? Give an instance in ancient times. How long do most grasshoppers live? Does a grasshopper spread its wings before it flies? Does it jump and fly together? Can it select the place for alighting? NOTE TO TEACHER.--=Field work in Zoology= should be systematic. Every trip has a definite region and definite line of study in view, but every animal seen should be noted. The habitat, adaptation by structure and habits to the environment, relations to other animals, classification of animals seen, should be some of the ideas guiding the study. The excursions may be divided somewhat as follows, according as opportunities offer: Upland woods, lowland woods, upland pastures, fields, swamps, a fresh-water lake, a pond, lower sea beach, higher sea beach, sand hills along shore, roadside, garden, haunts of birds, insect visits to flowers, ground insects, insects in logs.