12 SIXTH ANNUAL REPORT 



dency to which I have before alluded, toward a change of habit from 

 year to year, as the insect changes and extends its habitat: 



I found the Doryphora 10-lineata Say, at Port Austin, Michigan, 

 on June 19, 1872, feeding sparingly on young grass (too immature to 

 determine its species), on which the insect had deposited its eggs. 

 This was generally, though not always, in potato fields or their vicinity. 

 On July 20 (about a month later) I found the insect at Fort Gratiot, 

 Michigan, in large numbers, both larva and perfect states, in the vi- 

 cinity of potato fields which it had almost destroyed, devouring the 

 younger leaves and flower-buds of the common thistle {Clrsiura lan- 

 ceolaturii Scop.), which it was rapidly stripping. In the same neigh- 

 borhood I saw it on Pigweed {Aniarantus retroilexus L.), Hedge mus- 

 tard {Slsimhrimn oMcinale Scop.), the cultivated Oat, Smartweed ( Po- 

 ligonum hi/dropiper L), and the Ked Currant and Tomato of the gar- 

 dens, as well as the common Nightshade {Solaiiiuti nigrum L) ; of 

 which, with the exception of the Nightshade, iis more legitimate food, 

 it ate only the young leaves, and of them very sparingly. Two or 

 three weeks later 1 found the thistles devoured by it even to the thick 

 stems, so that all the leaves were stripped off", and the entire tops of 

 the plants hung down, almost severed. About the same time 1 saw 

 the insect feeding on the maple-leaved Goosefoot {Chen.opodium hy- 

 oridum L ), Lamb's quarter ( C. album L,), and Thoroughwort {Eupato- 

 rium pcrfoliatum L ), and on August 8, 1872, 1 found it, in both Ihe 

 larva and perfect states, voraciously eating the Black Henbane {Hy- 

 osciavins n\ger L.), on which was also to be seen an abundance of the 

 eggs. As tiie last mentioned plant is not native, having been intro- 

 duced from Europe, the beetle's fondness for it is more noteworthy. 



This growing ability to adapt itself to a greater variety of food- 

 plants will render its extermination and control all the more difficult. 



Several instances came under my notice where the beetles, in 

 early spring, entered hot-beds in great numbers and devoured tender 

 tomato and egg-plants. 



ITS PROGRESS K AST WARD 



Has continued during the year, and the avant cotiriers of the vast 

 army have pushed to the extreme eastern limit of ^^q^^ York* and into 

 the District of Columbia. f Mr. M. B. Bateham describes, in the OMo 

 Farmer^ how the waters along the shore of Lake Erie, in the extreme 

 N.E. corner of Ohio,were literally swarming with them ; and the Paines- 

 ville (Ohio) Tdegraph thus chronicles the passage over that town of 

 " clouds of Colorado Potato bugs, bound toward the setting sun" — 

 these " clouds," however, as 1 have been informed on good authority, 

 not being so dense that more than a few dozen could be seen at any 

 one time by a single person : 



*A c'oiTospoiulcnt (T. L. S.) of the Country Gentleman found it arouiul Delhi, in Dehnviire 

 Co., in the S. E part of New York; the specimens being pronounced afeniiine hy the editor of that jour- 

 n;d to wlioni they were sent. 



+ See monthlj' Rep. I)ep. Agr. for Aug. and Sept. , 1S73. 



