352 GENERAL BIOLOGY 



every green crop and weed as they go. During cold or damp weather 

 and at night they collect under rubbish, in stools of grass, etc., and at 

 such times almost seem to have disappeared; but a few hours of sun- 

 shine brings them forth as voracious as ever. When, on account of the 

 immense numbers assembled together, it becomes impossible for all to 

 obtain green food, the unfortunate ones first clean out the underbrush 

 and then feed upon the dead leaves and bark of timber lands, and have 

 often been known to gnaw fences and frame buildings. Stories of their 



Fig. 229. Long and Short Horned Grasshoppers. 



A. Order Orthoptera. Katydid, Microcentrum 

 retinerve. (From Sedgwick's Zoology, after Riley. ) 



B. Red-legged grasshopper (Melanoplus femur- 

 rubrum) : Ab, abdomen ; Ant, antennae ; E, eye ; M, 

 mouth ; T, thorax ; S, spiracles. 



incredible appetites are legion; a friend informs me that he still pos- 

 sesses a rawhide whip which they quite noticeably gnawed in a single 

 night. 



"By mathematical computation it has been shown that such a swarm 

 could not reach a point over thirty miles from its birthplace, and as a 

 matter of fact they have never been known to proceed over ten miles." 



There are other species and genera which do not migrate from their 

 native haunts at all. Many ingenious ways have been used to extermi- 

 nate them. Certain fungus growths on plants which the grasshopper 

 uses for food are fatal to him. So, too, is the little tachina fly already 

 mentioned. Such fungus growth and flies are sometimes developed to 

 assist in controlling injurious insects. 



The effect of a difference of temperature on insects is well illustrated 

 by the fact that there is only one annual generation of grasshoppers in 

 New England, while there are two in Missouri. 



Ditches are often dug in which the animals fall, or kerosene emulsion 

 is poured on water standing about, or placed in simple trough-like 

 wooden movable ditches. Even if the grasshopper crawls out of the oil 

 it dies shortly after. 



For the control of grasshoppers, see any of the books mentioned on 

 Economic Entomology, at the end of Chapter XXIV. 



