36 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



zones; and shells have occasionally been studied from this standpoint. 

 Yet particularly within certain areas insects are of great assistance in 

 indicating zone limits, and the only data available for study are faunal 

 lists, in which too often the exact localities of capture and the eleva- 

 tion are unrecorded. We generally even lack a knowledge which 

 zone a given insect particularly belongs to. 



Of course, many insects are so hardy and have such powers of flight 

 that they cannot be taken into consideration as evidence. Many 

 others, however, provide us with important information if we only 

 know how to use it. 



It may seem almost outside the realm of entomology or at least 

 economic entomology to be concerned with distribution except in the 

 most general way, and it is true that in a number of states — perhaps 

 a great many — all kinds of insects present at all are liable to be found 

 anywhere in the state where their necessarj^ food occurs. In many 

 other states, however, this is far from being the case and the determina- 

 tion of the zonal limits in those states as indicated by the insects and 

 supported by other animals and b}^ plants, can lead to modifications 

 in the crops raised, with direct benefit to agriculture. 



To illustrate this by the conditions found in Massachusetts: This 

 state is general!}^ considered as being mainly in the Transition Zone, 

 barely touched at one or two points on the south by the upper Austral 

 and on the north by the Boreal. A study of distribution shows, how- 

 ever, that the entire southeastern portion of the state, the Connecticut 

 Valley and two other inlets from the south are inhabited by upper 

 Austral forms to a greater or less degree, while quite an area in the 

 western end of the state and spots near its northern boundary have 

 many Boreal forms. 



Knowledge of this of itself, meant but little at first. But when the 

 elm-leaf beetle had become well established, it was finally discovered 

 that while it was a serious pest in the upper Austral sections and fre- 

 quently of some importance in the Transition Zone, it was never suf- 

 ficiently destructive in the Boreal areas to make treatment necessary. 



The elms of Massachusetts are one of her chief attractions, shading 

 her streets by their high arches, and growing to perfection. Their 

 value has in some cases been fixed at five hundred dollars per tree, and 

 nearly every town has thousands of them. Spraying for the elm-leaf 

 beetle is almost universal in the state and an expenditure of from five 

 hundred to twenty-five hundred dollars for this purpose each year is 

 anticipated as a part of almost every town financial budget. Accord- 

 ingly, when it was discovered that elms growing in the Boreal region 

 need not be sprayed, thus saving that much expenditure to the towns 

 concerned, the value of a knowledge of the zonal areas at once as- 

 sumed an economic importance heretofore unrecognized. 



