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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
closely related plant. Some recent experiments of my own with the 
Colorado potato beetle show this type of behavior very clearly. This 
insect will feed upon various species of Solanum belonging to two of the 
five sections into which the genus is divided; at least several of the species 
referred to the section that includes the original food-plant (5. rostratum) 
are readily accepted, as well as our common bittersweet (5. dulcamara) 
which falls in another section, that to which the potato belongs. The 
bittersweet and a large spiny African plant (5. marginatum) attract 
the beetles even when planted in close proximity to the potato. The 
ordinarily monophagous habit of the potato-beetle is thus clearly due 
to the composition of the flora and any significant change in the latter 
must have its effect upon the numerical abundance of the beetles, 
particularly on the population living at the expense of its economic 
food-plant the potato, which is planted from year to year without 
reference to the abundance of the beetle, while the supply of its un¬ 
cultivated food-plants varies inversely with the prevalence of beetles. 
Just as the supply of the food-plant necessarily limits - the abundance 
of the insects dependent upon it, so the number of insects competing 
for subsistence upon a single kind of plant influence one another greatly. 
Such competition does not however, lead to such a strict “survival of 
the fittest” and “elimination of the unfit” as theoretical considerations 
might lead us to believe. Several entomologists who have during re¬ 
cent years compiled lists of the insect faunae of dominant species or 
genera of plants under both natural and agricultural conditions, have 
been able to find long series of insects affecting almost any plant which 
they care to investigate. In more or less circumscribed areas these 
series of insects come into direct competition with one another when 
they depend upon the same part of the plant, such as the foliage, although 
indirectly all interfere with one another; even such diverse kinds as 
Aphids, defoliators, leaf-miners, stem and root-borers, etc. Under 
prevailing non-agricultural conditions, this competition is so much less 
keen than that between host and parasite that a phytophagous insect 
appears rarely or never to be actually threatened with extinction or 
even decimation by any failure of the food supply resulting from the 
ravages of competing species. It must be understood fully however, 
that I should by no means wish to imply that such competition extending 
over long periods of time might not readily lead to vast changes in both 
fauna and flora. Just as an extensive outbreak of some phytophagous 
insect like the American tent-caterpillar with its accompanying epidemic 
of parasites and other enemies may lead to the complete local ex- 
