OF WASHINGTON. 225 



Carolinian and upper Sonoran belt to Colorado, and is again 

 found upon the Pacific slope north to Washington. 



The American locust (ISchistocerca americana} is a tropical 

 and austro-riparian form, which apparently extends with ease 

 through many upper austral regions. It is common throughout 

 the southern States, from the District of Columbia to Texas, and 

 injurious broods have occurred in Illinois, Indiana and southwest 

 Ohio. It has been doubtfully reported from the vicinity of New 

 York city, and specimens have been taken in New Jersey as far 

 north as Newark and New Brunswick. The last number of the 

 Canadian Entomologist records the capture of a single speci 

 men in Canada. The note is by Mr. J. Alston Moffat, who 

 lives at London, in lower Ontario, at the borders of the upper 

 austral, and presumably the specimen was captured in the Cana 

 dian strip of this zone, although the actual locality is not given.* 



This species is one of the forms which would seem to indicate 

 that in a few cases, at least, the winter temperature must have 

 some effect in determining distribution. It is exceptional from 

 the fact that it hibernates in the adult condition, and we can 

 hardly avoid the conclusion that it is limited in its northern range 

 by circumstances which influence successful hibernation. Noth 

 ing is better known than that exceptional freezes may kill off 

 thousands of insects ; there must therefore be species whose suc 

 cessful hibernation is limited by certain degrees of cold. 



There are, then, among these species which we have just con 

 sidered, several enemies to cultivated crops which are apparently 

 unable to follow their food-plants into certain regions into which 

 their cultivation has been successfully carried. They are spe 

 cies which occur to me at first glance over the field, and closer 

 study will doubtless show others. There are, however, scores of 

 species in which no such limitation exists. Such are Leucania 

 unipuncta, Heliothis armiger, Pieris rapce and many others 

 which will readily occur to you. There are many potentially 

 cosmopolitan species. Even in the case of Leucania unipuncta 

 and Heliothis armigera, however, there seems at least a partial 

 end to injurious occurrences at the borders of the transition zone. 



The few facts just mentioned indicate that results of interest as 

 well as of practical importance can be gained from the plotting 

 of the spread and range of crop enemies. The fact that there 

 are limitations not dependent upon food with even a few species, 

 is of great importance, and it is a line of investigation which must 

 be followed up. 



Mr. F. M. Webster in his suggestive paper, " Some insect 



* Mr. Moffat has since written me that the specimen was taken in the 

 immediate vicinity of London. 



