BRANCH ARTHROPODA ; CLASS IN SECT A : THE INSECTS 163 



of the head to the base of the abdomen. By steady 

 swelling and contracting and slight wriggling, lasting for 

 half an hour to three-fourths of an hour, the old skin is 

 completely shed, and the wings spread out. In an hour 

 the wings are dry and the new chitinized exoskeleton 

 firm enough for flying, or crawling about, and in another 

 hour the locust begins to eat. 



The red-legged locust does considerable damage to 

 cultivated crops, but its injuries are insignificant compared 

 with the tremendous losses occasioned by a near relative, 

 the Rocky Mountain Locust (Melanoplus spretus}. This 

 locust has its breeding-grounds on the high plateaus of 

 the Rocky Mountain region, but it sometimes migrates in 

 countless numbers southeast over the plains and into the 

 great grain-fields of the Mississippi valley. Such migra- 

 tions occurred in 1866, 1867, 1874 (in this year eighteen 

 hundred and forty two families in Kansas were reduced 

 to destitution by the utter wiping out of their crops by 

 the locusts) and 1876. With the settling-up of the 

 regions injvvhich the Rocky Mountain locust breeds, there 

 seems to have come a change of conditions, so that no 

 great migrations have occurred since 1876. 



THE GREAT WATER-SCAVENGER BEETLE (Hydrophilus sp.) 



TECHNICAL NOTE. The great water-scavenger beetles are 

 large, black, elliptical insects common in quiet pools where they 

 may be found swimming through the water, or crawling among the 

 plants growing on the bottom. They are an inch and a half long 

 and are readily distinguishable from all other water insects except 

 the predaceous diving beetles (Dytictts). The antennae of Hydro- 

 philus, however, are thickened (clavate) at the tip, while those of 

 Dyticus are thread-like for their whole length. The beetles may 

 be readily collected with a water-net, and kept alive in glass jars 

 or aquaria in water containing decaying vegetation. 



External structure (fig. 39). Is the body of the water- 

 beetle composed of segments ? Can you make out three 

 body-regions, head, thorax and abdomen / As in the 

 locust the metathorax is fused with the first abdominal 



