NORTH AMERICAN ACRIDUDJE. 23 



are so exactly intermediate that they can be referred to neither 

 species with certainty. If intergradation prove to be the case, the 

 increased amount of pigmentation in the southern form is noteworthy, 

 paralleled as it is in other genera. Additional material in series, 

 and, if practicable, experimentation, is needed to determine the 

 relation of these forms and the possible effect of climatic conditions. 

 Other topics connected with the biological study of this group 

 of insects, such as coloration and stridulation, were given little 

 attention, owing to the limited time for observation in the field. 

 It is sufficient to say that many of the Oedipodinae collected (espe- 

 cially Trimerotropis > Scirtetica, Hippiscus, Psinidia, and Spharagemori) 

 exhibited in a high degree their customary phases of coloration 

 for concealment when at rest (see PI. 8, Fig. 2) and for display (recog- 

 nition or sexual coloration) when on the wing, in the latter case 

 accompanied by a crepitating flight which in itself attracts attention. 



SPECIES OF ECONOMIC IMPORTANCE. 



The only species met with in sufficient numbers to be of 

 economic importance were Schistocerca americana, Stenobothrus curti- 

 pennis, Melanoplus differentialis, M. atlanis, M. amplectens, and possibly 

 Chortophaga viridifasciata. But three localities were found where 

 any of these were abundant enough to cause considerable damage. 

 Schistocerca americana occurs throughout the entire region visited, 

 from the seashore to the tops of the highest mountains, but was 

 found in numbers only near Chattanooga, Tenn., where it was 

 accompanied by M. differentialis. M. atlanis also was observed nearly 

 everywhere and is perhaps the most dangerous, potentially, of any 

 species inhabiting the region. It was excessively plentiful at lyin- 

 ville, N. C., where its numbers threaten serious injury if they con- 

 tinue to increase. In the high grassy coves of Roan Valley, on the 

 south side of Roan Mountain, the fields were alive with adults and 

 young of M. amplectens (blatchleyi) a species which is capable of doing 

 much damage locally, but, being short-winged, is unable to extend 

 its ravages far. Stenobothrus curtipennis also was very plentiful at 

 lyinvilie and Roan Valley. 



Inquiries made as to damage by locusts elicited little definite 

 information. A few complaints were received of injuries to tobacco 

 leaves occasionally, and to young crops in the spring. From the 

 description furnished and the life history of the species it is suspected 

 that Chortophaga viridifasciata may be the culprit in the latter case. 

 Any locust outbreak occurring is likely to be of rather local char- 

 acter and probably could be suppressed promptly at small expense. 



