600 EVOLUTION OF ANIMALS Part V 



of grasshoppers were pioneer insects in the warm dampness of the Car- 

 boniferous Period, when primeval forests were being slowly overspread and 

 were turning to coal beds. Their fossils show that since then grasshoppers and 

 cockroaches have changed far less than most insects. 



Grasshopper. Grasshoppers belong to the family Locustidae, the locusts or 

 short-horned grasshoppers with antennae shorter than the body. They include 

 the common red-legged grasshopper (Melanoplus femur-rubrum) , the "Caro- 

 lina locust" (Dissosteira Carolina), the "Rocky Mountain locust" (Melano- 

 plus mexicanus) , and the short-winged lubber grasshopper of the south, often 

 studied in laboratories. The following discussion applies in general to any one 

 of these. 



The names grasshopper and locust are confusingly applied even to the same 

 species. Grasshoppers are permanently resident, solitary species such as the 

 common red-legged one. "Locusts" are migratory grasshoppers, such as the 

 Rocky Mountain locusts that periodically produce enormous populations, com- 

 pletely exhaust the food in their own region and then move from one new 

 feeding ground to another. In 1933 and before and since then, "Rocky Moun- 

 tain locusts" have swarmed over the country from the Rocky Mountains east- 

 ward nearly to the Mississippi River, devastating com and wheat fields and all 

 ground vegetation before them. 



Ecology. Grasshoppers flourish in sunlit fields of grass and grain. The 

 young ones hatch in early spring, by July are usually abundant, and in August 

 sprays of grasshoppers arise wherever long grass is disturbed. 



Food and Relationships. A great element of success in life is the habit of 

 living on common food. The success of the tribes of grasshoppers is due to this 

 habit. No other invertebrates consume grass and grains in such quantities. 



Toads, frogs, owls, meadowlarks, chipmunks, and ground squirrels all feed 

 upon grasshoppers. Parasites also beset them, young hair worms that bore into 

 their bodies, red mites that hang from them like brilliant beads. Enough grass- 

 hoppers to produce a plague would appear every year were it not for the mis- 

 haps that befall the eggs, the attacks of parasites, winter freezing and thawing, 

 spring floods, skunks and ground moles that nose them out of the ground, and 

 their great enemies, the larvae of blister beetles. A nicety in seizing an oppor- 

 tunity is exemplified by certain small wasps (Lepidoscelio) which ride about 

 on the females until they lay their eggs, and then deposit their own eggs be- 

 side them (Fig. 30.9). 



External Structures and Functions. Like other agile animals, grasshoppers 

 are bilaterally symmetrical. The body consists of three divisions, the head, the 

 thorax, the abdomen (Fig. 30.10). 



Head. The head is a hard capsule, composed of immovable plates or 

 sclerites. The eyes and antennae, mandibles, maxillae and labium are believed 

 to represent different segments in the wormlike ancestors. There are two kinds 



