42 



THE AMERICAN ENTOMOLOGIST. 



and the south-west corner of Michigan ; and final- 

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

 wliich lies nearl.v in the centre of that State, as 

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

 of that city; and the agricultural papers have 

 since recorded its appearance in Marion county, 

 which lies in the geographical centre of the 

 State. Thus it appears that its average annual 

 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 any 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 entii-ely distinct, but very closely 

 allied species, the Bogus Colorado Potato-bug 

 (^Doryphora juncia, Germar), and the True 

 Colorado Potato-bug {Dorypliora W-h'neata, 

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

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

 cently ascertained, through the kindness of Mrs. 

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

 feeds there in the larva state upon the horse- 

 nettle (Solanum caroUnense, Linn.), a wild 

 species of potato, which grows, according to 

 Dr. Asa Gray, "from Connecticut to Illinois 

 and southward."* The latter species, as has 

 been already stated, only 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 Rocky Mountain region. Again, the 

 former species 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 yeai-s, without ever having been known to 

 attack this plant, which has been growing all 



• In 1803 Mr . Glover stated that he "had found an insect 

 similar to the Tea-striped Spearman [or true Colorado Po- 

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

 Department Rep . , p. 57!)). In 1867 he assured us that this 

 insect, found hy him on the horse-nettle in Georgia foiu' 

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

 and that ' * a Ttli". Walter had also found it feeding upon tlie 

 Egg-plant in Montgomery, Alabama." We om-selves dis- 

 covered this same species in Kentucky in lS(i4, feeding in 

 conjunction with its larvae upon a plant, which we are now 

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

 and in 1S6S we have met with it In Missouri in great nimi- 

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

 larvx; and in one instance the larvic of both the true and 

 tile bogu.s species occurred in comi)auy. Thus it appears to 

 iuhabitat least five southerly regions, namely South Illinois, 

 Missouri, Kentucky, Georgia and Alabama. 



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

 probable that it will do so at any futui'e time. 

 The latter species, on the other hand, acquired 

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

 the Eocky Mountains, when for the first time 

 the potato was introduced there, some twenty 

 j'ears ago ; and from that region the potato-feed- 

 ing race of tliis iHsect has since been spreading 

 further and further every year towards the east. 

 Finally the bogus Colorado Potato-bug is more 

 peculiai-ly a southern species, occurring in the 

 more southerly portion of Illinois, and in Mis- 

 souri, Kentucky, Georgia, and probably Ala- 

 bama, while 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; while 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 indefinitely long 

 time in the country that lies to the east of the 

 Mississippi river, or whether it is not the bogus 

 Colorado Potato-bug that has there been mis- 

 taken for it, wliile the true Colorado Potato-bug 

 has iu reality emigrated into that country from 

 the Rooky Mountainregionwithinthe 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 tliis 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 the great potato-growing 

 State of Michigan, and finally pass eastwards 

 into Pennsylvania, New York, and New Eng- 

 land. "We make no apology, therefore, to our 

 readers for presenting them with the complete 

 history of these two insects, copiously illustrated 

 by figures, and for pointing out the minute but 

 invariable characters winch distinguish them, 

 both iu the larva and in the perfect beetle state. 

 Tliis 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. 



The Trae ami tlio Itogiis Colorado Potato-l)iig. 



Figure 3;1 b, b, b, gives a view of the larva of 



the true Colorado Potato-bug, in various posi- 



