42 



THE AMERICAN ENTOMOLOGIST. 



and the soutli-'west corner of Michigan ; and final- 

 ly, in 1868, it has reached Danville, lud., a point 

 which lies nearly in the centre of that State, as 

 Tve learned some time ago from Mr. A. Furnas, 

 . of that city; and tlie agricultural papers have 

 since recorded its apiDcarance in Marion county, 

 which lies in the geographical centre of the 

 State. Tims it appears that its average animal 

 progress towards the east has been about sixty- 

 two miles. At the same rate of progression it 

 will touch the Atlantic ocean in ten years from 

 now, or A. D. 1878. 



"But," it will be asked, "how could am- en- 

 tomologists make the mistake of supposing that 

 the Colorado Potato-bug had always existed in 

 the Northwestern States?" The answer is, that, 

 as was proved three years ago in the article al- 

 ready referred to, they inadvertently confounded 

 together two entirely distinct, but very closely 

 allied s^Decies, the Bogus Colorado Potato-bug 

 {Doryphora juncia, Germar), and the True 

 Colorado Potato-bug {Dorypliora 10-Uneccta, 

 Say) . The former of these has existed in Illi- 

 nois from time immemorial ; and, as we have re- 

 cently ascertained, through the kindness of Mi-s. 

 H. C. Freeman, of Cobden, South Illiuois, 

 feeds there in the larva state upon the horse- 

 nettle {Solanum caroUnense, Linn.), a wild 

 species of potato, wMch grows, according to 

 Dr. Asa Gray, "from Connecticut to Illinois 

 and southward."* The latter species, as has 

 been already stated, orAy emigrated into Illi- 

 nois in 1864, and in its native home, the 

 Eocky Mountains, feeds naturally upon an- 

 other wild species of potato, which is quite 

 distinct from the horse-nettle, and is peculiar 

 to the Eocky Mountain region. Again, the 

 former sjjecies has never yet been known to 

 attack the cultivated potato, and in all likelihood 

 never will do so ; for, as it has existed in Illinois 

 for at least 14 years, and in Georgia for at least 

 44 years, without ever having been known to 

 attack this plant, wMch has been growing all 



* In 18(33 Mr . Glover stated that he ' ' had found an insect 

 similar to tlie Ten-strix^ed Spearman [or true Colorado Po- 

 tato-bug] on the common horse-nettle in Georgia." (,Agr. 

 Department Rep . , p. 579). In 1867 he assured us that this 

 insect, foimd by him on the horse-nettle in Georgia four 

 years before, was the bogus Colorado Potato-bug (Z>. juncta), 

 and that ' ' a Mr. Walter had also found it feeding upon the 

 Egg-plant in Montgomery, Alabama." We ourselves dis- 

 covered this same species iu Kentucky in ISG-t, feeding in 

 con,iunction with its larvce upon a ijlant, "which we are now 

 satisfied could have been nothing else but the horse-nettle ; 

 and in 1868 we hiive met with it in Missom'i in great num- 

 bers, fceiling upon the same plant, in company with its 

 larva;; and iu one instance the larviB of both the true and 

 the bogus species occurred in company. Thus it ajipoars to 

 inhabit at least five southerly regions, namely Soutli Illinois, 

 Missouri, Kcntuclvy, Georgia and Alabama. 



that time in these two States, it is not at all 

 probable that it will do so at any future time. 

 The latter species, on the other hand, acquired 

 tliis habit, as was shown before, in the region of 

 the Eocky Mountains, when for the first time 

 the potato was introduced there, some twenty 

 yeai'S ago ; and from that region the potato-feed- 

 ing race of tliis insect has since been spreading 

 further and further every year towards the east. 

 Finally the bogus Colorado Potato-bug is more 

 peculiarly a southern species, occurring in the 

 more southerly portion of Illinois, and in Mis- 

 souri, Kentucky, Georgia, and probably Ala- 

 bama, wliile the true Colorado Potato-bug is 

 originally an Alpine species, its native home 

 being the canons (kanyons) of the Eocky Moun- 

 tains, and it therefore thrives best and spreads 

 fastest in the more northerly regions, such as 

 Nebraska, Iowa, Minnesota, Wisconsin and 

 North Illinois ; wliile in Southlllinois, Missouri, 

 and Kansas, it neither thrives so well nor spreads 

 so rapidly. 



The question whether the true Colorado 

 Potato-bug has existed for an indfefinitely long 

 time in the country that lies to the east of the 

 MississipiDi river, or whether it is not the bogus 

 Colorado Potato-bug that has there been mis- 

 taken for it, while the true Colorado Potato-bug 

 has in reality emigrated into that country from 

 theEocky Mountain region within the last fouror 

 five years, may seem to some of merely theoretical 

 interest. It is, however, of great practical impor- 

 tance. On the first supposition it is not probable 

 that this bitter enemy of the potato will travel 

 onwards and onwards towards the Atlantic ; on 

 the second supposition it will most likely invade 

 Oliio within a year or two, spread like a devour- 

 ing flame through tlie great potato-growing 

 State of Michigan, and finally pass eastwards 

 into Pennsylvania, New York, and New Eug 

 land. We make no apology, therefore, to our 

 readers for presenting them with the complete 

 liistory of these two insects, copiously illustrated 

 by figures, and for pointing out the minute but 

 invariable characters wMch distinguish them, 

 both in the larva and in the perfect beetle state. 

 Tins is the first time that the larva of the bogus 

 Colorado Potato-bug has ever been figured and 

 scientifically described ; and our readers have to 

 thank Mrs. Freeman for the opportunity of be- 

 coming acquainted with the points in which it 

 differs from the larva of the true Colorado 

 Potato-bug. 



Tlio True and tlio ISogus Colorado Potato-bng. 



Figure S3 b, b, b, gives a view of the lai-va of 

 the true Colorado Potato-bug, in various posi- 



