1940] Food Preferences of Colorado Potato Beetle 
39 
States at a much earlier date. Its spread may have followed 
the trails of the early Spanish explorers aided by the bur- 
like fruit which is readily transported on the fur of animals 
or clothing of man. Later this plant became more sparingly 
naturalized further northward and eastward under locally 
arid conditions like those prevailing on waste land or rail- 
road ballast. That this plant may be actually native to the 
drier parts of our southwestern states is quite possible, but 
at any rate it appears to have been the preferred food-plant 
of the potato-beetle during the earlier half of the nineteenth 
century. There is also a native potato in this same region, 
Solanum fendleri Gray, nee Heurck & Muel. (S. tuberosum 
boreale Gray) which extends from Western Texas to Ari- 
zona and Mexico in moist transition areas but there are 
apparently no records that indicate whether or not this wild 
potato has ever served as a food-plant for the beetle. That 
it might do so is very likely since it is very similar to the 
cultivated form, although as the two plants (S. fendleri and 
S. rostratum) do not occur under similar ecological condi- 
tions passage from one to the other could not commonly oc- 
cur. 
Before 1860 the potato-beetle found a highly acceptable 
food-plant in the potatoes that were cultivated in the region 
where it then occurred and it was recognized as early as 
1859 as an established pest in gardens. Thenceforth it 
spread into the eastern and southern states and later to the 
Pacific region. It has continued to prefer the potato to other 
species of the genus Solanum (s. lat.) , although several other 
genera of Solanacese are sometimes attacked in a more spo- 
radic way. Thus it is well known that the larvae are fre- 
quently destructive to egg-plants ( Solanum melongena) in 
gardens and that they appear occasionally on tomatoes 
( Lycopersicum esculentum) , ground cherry ( Physalis spp.) 
and on certain varieties of cultivated tobacco ( Nicotiana ) 
that develop a low nicotine content in the leaves. 
The sporadic occurrence of the beetle on some of its less 
favored food-plants may indicate the presence of separate 
strains or genetically distinct types, especially as it cannot 
always be traced to the absence of the preferred potato food- 
plants in the immediate vicinity. 
With this question in mind a series of 24 species of So- 
