1910.] PUBLIC DOCUMENT — No. .SI. 75 



allv (loiic in this locnlitv, mid llicii trcntcd with a iiiixini'c of 

 ]*aris oreeii and diisl until a i;i-ccnish cohn- is peiv('])til)k', it will 

 not he eaten hv wire worms. 'Jdiese experiments will he rejH'ated 

 the eoniino- ycai-. 



Witliin the last Iwcntv years Massaehnsetts has heen invaded 

 hy several injurious insects whieh naturally belong farther 

 south. Among these may he mentioned the (dm-leaf beetle, San 

 Jose seale, eommon asparagus beetle and the twelve-spotted 

 asparagus beetle. How far noi-tli these ])ests can s])read and be 

 injurious is as yet unknown, but it is certain that there are 

 limits to this spread, and for at least some of those named it 

 seems quite cei'tain that these limits nuiy prol)ably be found 

 within this State. It is not a particular degree of latitude 

 Avhich marks the barrier to their further s])read northwai-d, but 

 rather climatic conditions, and the^e are modified by elevation. 

 In other words, the limiting lines of distribution appear to be 

 isothennal in their nature, though their exact character is as yet 

 unsettled. It nuiy be the average winter temperature, the mini- 

 mum winter temperature or some other factor which settles 

 whether an insect shall be a pest at any given place near its 

 northern limit. In any case, the determination of this cause, 

 and the resulting conclusion that an insect will or will not 

 become injurious at a given place, will be of much importance. 

 As an example of this it may be stated that such evidence as is 

 now available, though as yet too little to be conclusive, suggests 

 the belief that in ]\Iassaehusetts the elm-leaf beetle will not be 

 likely to be of much importance in those parts of the State 

 which are more than a thousand feet above sea level, exce])t, 

 ])erhaps, near the southern edge of the State, where the altitude 

 is to some extent offset by the more southern latitude. To work 

 out problems of this nature fuller meteorological data are needed, 

 as well as more observations of the disti-ibution of the insects 

 themselves, and studies of this kind have been in progress for 

 several years, and will be continued. 



Parasitism as one of nature's methods for the control of in- 

 jurious forms has long been recognized. It has been utilized 

 in numerous cases by man, who has conveyed parasites from one 

 country to another to attack their hosts, wdiicli have already l)een 

 by accident thus transferred. P( rhaps the most gigantic exi)eri- 



