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NINTH ANNUAL REPORT 



abound in wet springs preceded by one or more very dry years. They 

 are preyed upon by numerous enemies, which so effectually check 

 their increase, whenever they unusually abound, that the second 

 brood, when it occurs, is seldom noticed ; and two great Army Worm 

 years have never followed each other, and are not likely to do so. 

 They may be prevented from invading a field by judicious ditching ;. 

 and the burning over of a field, in Winter or early Spring, effectually 

 prevents their hatching in such field. 



THE WHEAT-HEAD ARMY WORM.- 



Guen. 



■Leucania alhilinea* 



[Fig. 14.] 



There can be no more tangible evidence, in present time, of the- 

 truth of evolution, and of the constant modification in habit, and con- 



sectaneous modification in structural and col- 

 orational characteristics among animals, espe- 

 cially among the lower classes, than the fre- 

 quent appearance, as destroyers of our crops,, 

 of insects that were never reported as injurious 

 before. When entomologists speak of a new 

 insect enemy, they are not to be understood as 

 ^ implying a new creation. In a great majority 

 of instances the species has long before been 

 known to them, and has simply, for one reason 

 and another, become unduly multiplied so as 

 to force itself upon the attention of the com- 

 mon observer. In other cases it is new only 

 to a particular locality to which, from some 

 other region, it has been introduced. Yet in. 

 the most restricted and well worked-up locali- 

 ties, speaking either zoologically or botan- 

 ically, new forms appear, and old forms some- 

 times disappear, in a manner which can scarce- 

 ly be explained, except by the extinction of the 

 one and birth of the other through modifica- 

 ^^^J^a^\^'i''-,^^i^s-ZiJ'^zr-,^^^'^- Few naturalists at this day doubt that 

 iiarifi'.*"'' ^''^ "''^^'''^'^"new forms have thus originated in the past. 



*As will be shown at the close of this article, tliis insect is quite variable ami has recencd another 

 name. I employ the above name simply because it is appropriate and be.'ause llie insect lullv agrees 

 withGuenee's published description. To say alhilinea Huebn, carriesno such dciiuite idea, and Tia/rei/i 

 Grote is in my opinion but a variety. There is and always must be doubt as to wlitit alhilinea Jiuebn. 

 virtually is, since it is lounded mainly on a ligure ; and where there is such indecision it is, in niy judg- 

 ment, and in that of many others, best to discard Hubuer. It is lor this reason that I consider Guenee s 

 description original, as applying to the species imder consideration, and that his name should not L»e 

 superceded by any other under which the insect may have been subsequently delintd. 



