118 COACTION: THE INTERRELATIONS OF ORGANISMS 



life histories were known, a compilation of food habits was made from 

 this monograph. Eleven species were thrown out because of restricted 

 catches of new species, or because the host plant was unknown, etc. 

 The percentages of the 240 species considered are shown below: 



Per Cent 



A. On food plants belonging to more than 10 genera 2 



B. On food plants belonging to 2 to 10 genera 31 



C. Only genus named — several species implied 30 



D. Genus and one or more species cited 10 



E. On a single species 27 



100 



The food plants of some of these in the last category are known 

 only in Illinois, and thus the percentage in the last item may be very 

 materially reduced with further study throughout their range. In gen- 

 eral, there is a considerable number of coactors that are confined to a 

 single genus or even species of host plant, though the general flexibility 

 of food relations suggests that all supposed instances of such restric- 

 tion demand especially careful and thorough investigation. 



Seeds and fruits are particularly subject to attack by many species 

 of birds and some small mammals and numerous insects, by reason 

 of the relatively large amounts of food stored in them, but roots, 

 subterrene shoots, stems, leaves, and flowers are each the object of a 

 host of coactions, especially on the part of insects and a few birds. 

 Further distinctions may arise from the nature of the tissue con- 

 cerned, as in woody or herbaceous stems, the pith of a sunflower, or a 

 stone, seed, or pulp of a fleshy fruit. Finally, either living or dead 

 parts of tissues may be utilized, and sometimes this difference in con- 

 dition is immaterial to the coactor. 



In addition to the central coaction of eating, there are a number of 

 related processes such as collecting, harvesting, storing, and planting. 

 These may be simple and general in character, as with most of the 

 animals concerned, or they may be highly specialized, as with the 

 harvester ants and the fungus cultivators. So far as these are perti- 

 nent to the present treatment, they will be considered under the 

 respective groups. 



RELATIONS OF FOOD COACTIONS TO THE COMMUNITY 



A proper ecological approach to the study of food coactions is one 

 that brings out the community interactions. The investigator first 

 learns what foods are present and the quantity of each in the com- 

 munity or communities which the coactor frequents, and then pro- 



