COLORADO POTATO-BEETLE. 163 



their increase by devouring their eggs. Bat there have been reports, 

 from many localities, of a diminution in the numbers and destructive- 

 ness of these insects beyond what these agencies would account for. 

 It was a common remark, after the season was somewhat advanced, 

 that the Potato-bugs were not nearly so bad this year as they were the 

 last. In the Agricultural Reports for July were such items as the fol- 

 lowing : 



"Lapeer county, Michigan. — The potato crop looks fair. The old 

 bugs have nearly disappeared ; the young ones may yet do some dam- 

 age." 



"Green Lake county, Wisconsin. — Bugs leaving. They have left a 

 few eggs and some young bugs, but the latter are doing no harm. The 

 crop looks well." 



"Howard county, Indiana. — The Colorado-bug has almost disap- 

 peared." 



"Benton county, Minnesota. — Colorado-bug disappearing. Old ones 

 have about all gone ; the young ones do not seem to thrive as in pre- 

 vious years." 



Now, these may have been exceptional cases, or rather exceptionally 

 strong cases ; but taken together and in connection with other obser- 

 vations, which we have not here space to record, they seem to intimate 

 pretty clearly that the Colorado-beetle is not exempt from the opera- 

 tion of those general and imperfectly known laws or conditions which 

 are known to affect other insects, and which cause them to be compara- 

 tively rare one year and abundant another. A curious paralellism may 

 be traced between the inroads of noxious insects and the prevalence of 

 epidemic diseases, both being much more virulent and destructive in 

 the earlier than in the later periods of their prevalence. 



If this view is correct, it gives us reason to hope that though this 

 destructive insect may not become wholly exterminated, it may never- 

 theless cease, in a few years, to be the terrible scourge that it has been 

 for the live or six years last past. 



As the Colorado-beetle originated from the far West, and has been 

 steadily progressing eastward, the question has been anxiously asked 

 by agriculturists, whether, in proportion as these insects overrun new 

 territory, they will subside in the sections first attacked. The experi- 

 ences of the past year go far to answer this question in the affirmative. 

 Whilst the most disastrous reports have come from the more recently 

 invaded States of Indiana and Michigan, the State of Iowa, which these 

 insects ravaged for a year or two before they crossed the Mississippi 



