February, ’23] 
BRUES: FOOD CHOICE AND INSECT ABUNDANCE 
49 
is well known to every one present, the larvas of this moth have two 
very favored food-plants, maize and cotton, several less favored ones 
such as tomato and tobacco and a number of others to which they will 
quite readily transfer their attention with practically no persuasion. 
Maize is undoubtedly the most favored food, but no strains have been 
developed preferring maize or cotton respectively and this is undoubtedly 
due to the seasonal distribution of the parts of the plants attacked, 
namely the unexpanded tassels and soft ears of maize and the buds and 
green bolls of cotton which follow one another during the growing 
season and offer a continuous but changing food-supply not only to 
the several broods each summer, but regularly from year to year. 
Species exhibiting such plasticity in their behavior tend to become 
extremely abundant where their several food-plants are associated, and the 
species just cited has been favored by an unusually happy combination 
of circumstances. If we apply such a principle to another insect like 
the cabbage maggot ( Pegomyia ) it is evident that this species should be 
able in the ordinary truck garden where cabbages and a succession of 
radishes are grown, to avail itself of a continuous supply of succulent 
food. In connection with this species, I am not aware, however, that 
any investigations have been made to ascertain how readily the flies 
shift from one food-plant to another in successive generations, and the 
studies of the English entomologist Cameron on related species suggest 
that the cabbage maggot may have phytophagic varieties or strains, 
which tend to remain from generation to generation on the same food- 
plant. So far as oligophagous forms are concerned, it is evident that 
aside from the mere existence of several acceptable food-plants, the 
numerical abundance of each species is influenced not only by the prox¬ 
imity of the several food-plants, but by the ease with which a shift is 
made from one favored food-plant to another; and furthermore that all 
insects do not react similarly when the opportunity for a change of food- 
plants is presented to them. 
The Oligophagous habit passes by close intergrades to the monoph- 
agous type of feeding. Frequently the difference is only apparent 
and due to incomplete knowledge as has been often demonstrated. 
Again it is easily conceivable that the areas occupied by the several 
food-plants may be separated geographically, in which case the strains 
feeding on one plant will never have opportunity to pass to another 
and may become so wedded to this food that they will refuse to leave it. 
On the other hand as is well known from the behavior of certain introduced 
insects a sudden taste may be shown for a strange, though usually 
