316 



PSYCHE. 



[February iSgg. 



a field of any particular character it is 

 possible to predict with a high degree 

 of certainty what species of locusts will 

 be found therein. 



This susceptibility to local physical 

 conditions is a very important attribute 

 of the group in this connection. Most 

 cultivated crops and many wild plants 

 are equally susceptible to the same con- 

 ditions, — a fact especially noticeable 

 in parts of California where exposure 

 to sea-wind or direct sun-rays produces 

 a marked difference in the amount and 

 character of the vegetation on contiguous 

 hill-slopes, and also in parts of New 

 England, where fields a few acres in 

 extent are seldom homogeneous in char- 

 acter. 



Now the successful cultivation of 

 crops by the individual agriculturist is 

 dependent on the factor here involved : 

 a close adaptation of a particular species 

 or variety to its environment, — the en- 

 vironment being constituted by condi- 

 tions, as has been said, often extremely 

 local in character. For this reason it 

 seems probable that close stud}- of the 

 distribution of this group of animals 

 would prove of exceptional value in 

 delimiting the smaller details of life 

 zones, especially in the more valuable 

 narrow extensions of such areas, whose 

 importance has been indicated by Dr. 

 Merriam. 



It is perhaps worth while to point 

 out in this connection that species be- 

 longing to a southern zone and adapted 

 to a sandy soil may find their northern 

 limit considerably higher up, both lati- 

 tudinally and vertically, than other spe- 



cies equally characteristic of the same 

 zone but restricted to a damp and heavy 

 soil. More rarely the reverse arrange- 

 ment would occur. Consequently, that 

 the final limit of a given zone would 

 vary according to the species selected 

 to delimit it and the adaptation of these 

 species to the physical conditions of the 

 locality in question. 



So much by way of preface and in 

 regard to details. It remains to be seen 

 whether the distribution of the group is 

 of value in determining the broader 

 features of life zones. For this purpose 

 let us turn our attention to a district 

 sufficiently well-known to allow a com- 

 parison to be made. Such a district 

 we have in New England, whose locust- 

 fauna, with the exception of northern 

 and eastern Maine and western Ver- 

 mont, is as well known as that of any 

 part of the Union of equal extent and 

 whose faunal areas also have been the 

 subject. of study. While it is true that 

 a great deal remains to be done in 

 working out the details there is suffi- 

 cient available to enable a close ap- 

 proximation to the truth to be secured. 



Geograpliically considered the locusts 

 of New England fall into three groups : 

 — 1st, species believed to be distributed 

 over practically the entire district ; 2nd, 

 species known to be distributed over but 

 a part of the district ; 3rd, species whose 

 distribution — either from local char- 

 acter or positive rarity — is insufficiently 

 known. Of these groups the first is of 

 interest in showing the relation of New 

 England to the rest of the country ; the 

 third may be ignored for the present ; 



