49 



Mekmoplm femur-rubrum DeG. — Throughout the region in cultivated districts. 



Melanoplus plurribeus Dodge. — At Haigler, Nebr., on weeds and other rank vege- 

 tation. 



Melanoplus lakinus Scudd. — Western Kansas and Nebraska and eastern Colorado, 

 on Russian thistle and lamb's-quarters. 



Melanoplus occidentalis Thorn. — On the open prairie, west of the one hundredth 

 meridian, in all four States in which work was done during the summer. 



Melanoplus aUanis Riley. — Cultivated grounds generally, but less numerous than 

 M. femur-rubrum. 



Melanoplus bivittatus Say. — In nearly every locality where locust depredations were 

 reported, and especially in cultivated districts. 



Melanoplus differentialis Filler. — Possibly the most abundant of all the species of 

 locusts mentioned in this paper, and present in all localities except those in the 

 extreme northwestern corner of Nebraska and central Wyoming. The chief insect 

 in alfalfa districts. 



Of these the following species seem to be confined more or less closely to special 

 food plants, and are therefore somewhat restricted in their distribution: 



Hesperotettix praterms Scudd. — On Solidago graminifolw. or S. caroliniana. 



Hespcrotetfix viridis Thorn. — On Haplopappus spinvlosus. 



Hesperotettix speciosus Scudd. — On Helianthus, several species. 



Moloplus lurnbullii Thorn. — On Russian thistle and lamb's-quarters. 



Melanoplus bowditchi Scudd. — On Artemesia longifolia. 



Melanoplus lakinus Scudd. — On Russian thistle and lamb's-quarters. 



Those which are especially noticeable as enemies of cultivated crops are Melanoplus 

 differentialis, M. bivittatus, M. femur-rubrum and M. aUanis, along with M. packardii. 

 The remainder are chiefly grass eaters or feed upon various uncultivated plants. 



WHY LOCUSTS INCREASE ABNORMALLY. 



After having carefully .scrutinized the notes relating to the locust 

 problem in the region embraced in the investigations chronicled on 

 the preceding pages, together with all other available information on 

 the subject in general, the writer has come to the following conclusions 

 as to why grasshoppers increase abnormally: 



(1) The growing of alfalfa without regularly disking the ground each spring. 



(2) The abandoning of once cultivated fields, and permitting thereon the growth 

 of weeds and other rank herbage. 



(3) The very general carelessness of allowing weeds and other rank growths to 

 flourish along roadsides, irrigating ditches, and railway tracks. 



(4) The presence in great abundance of the Russian thistle in portions of the 

 country year after year. 



(5) The non-burning of prairies over wide areas for a number of years in succession. 



(6) The undue destruction of game and other insectivorous birds over wide areas. 



(7) The recurrence of unusually wet years after several abnormally dry ones. 



B The absence of insect enemies and diseases brought about by various causes, 

 chiefly climatic. 



It is but just to state here that lack of space prevents a very elab- 

 orate discussion of these various reasons for locust increase. 

 8258— No. 38—02 -i 



