15 



iiiid vvhic'li nijiy, coiiscMiiiciiUy, Ik; |)r;u-iicully i-^tiorcd by tiu; r;ii-iri(!r an 

 insi^iiiCicuiit. 



J liavo tli()Ufi;lil it host tlial Uw, first <^v<m\) should In; iriad(! as sinall as 

 is reaKona})le and safe, and liavo phiMul no spccicis in it, vvhicli tli(!ro was 

 not positive reason 1o consider as a destructive! corn p(!st. 'I'lie second 

 group, on the oth(!r liand, 1 liave made to include all oi" the otlnsr species 

 which are known to liave any tangible economic significance whatever. 



The first grou|) may be said to contain those s|)(!ci(;s (U)iicerning 

 which every practictal corn farmer should know the (wsJMitial facts; th(! 

 second group, those additional species which should be f;iniili;i,rly known 

 to the economic entomologist; and the third group, thos(! which iire of 

 interest cliiefiy to the general entomologist — thestudcsnt, of (iiitomological 

 ecology — who wishes an exhaustive; knowledge of the (nitomology of l,h(! 

 corn ])lant. 



Notwithstanding this distiiKaion, it should Ik; r(!m(;mberod that n(!ga- 

 tive knowledge is sometimes little less valuable; than positive; tJiat it 

 may sometimes be as irdx;resting, and even as im[)ortant, for a farmer to 

 know that a s[)eci(!S appearing for the first time in hi^ fields is not defi- 

 nitely injurious as it is to recogniz(! it at on(;e as an ins(!ct enemy. TIk; 

 more he (;an learn, consecjuently, of the great asso(;iation of corn insects 

 treated in this r(!|)ort, t,h(; IxstJcr prepared Ik; will be to handk; his crop 

 intellig(!ntly utid(!r all conditjons. 



Jt nuist, of course, be admitted that the dividing lines b(;tween these 

 groups are more or less arbitrary, and at best but poorly (Ujfined, the 

 division between the first and second being especially hard to es1,ablish. 

 An insect may be highly important to corn cult\n-e at som(! times and in 

 some parts of tli(; country, and of little or no importance elsewh(!re and 

 ordinarily, and dilTcienccjs of judgment will miavoidably arise as to the 

 group in which a giv(!n species should be placed. The history of economic 

 entomology makes it also virtually sure that certain sp(!ci(!S now prop- 

 erly placed in one of the less important groiifjs will n;((uire li(;r(!aft(!r t,o b(! 

 transferred to a more important one, and the group division Iksh; pro- 

 posed may, on this jiccoiuit, become; more; or less ina(;cin'at,(; in course of 

 time. 



TIk; reverse i)roposition is, liowever, nuich less lik(;ly to be true. It 

 will rarely occur tliat a species once recognized as serious'y destructive 

 to (torn will dro[j to an inferior place on the list. It sometimes hap[)ens, 

 indeed, that an ali(;n ins(;ct species is much more numerous and d(;struc- 

 tiv(; for a iaw y(;ars following upon its first a|)pearance in the country 

 than it ever is again, but, as a matt(;r of fact, no single corn ins(!ct of 

 any consid(;rabl(; im[)ortance is such an alien species — has conu; into 

 the country, thai, is t,o say, sitice corn became an im[)ortant Am(;ri(;an 

 crop. 



