COMPETITION 159 



striking of these are probably represented by insects and a few birds. 

 In one direction, the beginning of such a rehition is to be seen in cases 

 of trophallaxis where tliere is an actual exploitation of the larvae 

 without an adequate return, as in certain social wasps (Wheeler, 

 1923:83). An advance upon this relation is made by such ant guests 

 as Lomechusa and its relatives, which beg food from their hosts. The 

 step from beggary to thievery is a short one, as is shown by Antenno- 

 phorus in particular {loc. cit., page 226) , as well as by the thief ants 

 and certain mymecophiles {loc. cit., pages 201, 221). When eggs or 

 larvae are stolen, thievery often leads to slavery in varying degree 

 {loc. cit., page 207). 



Crowding brings about disoperation among animals, especially in 

 families or colonies of aquatic organisms, and this may be expressed 

 in terms of growth, reproduction, or survival. Aggregation probably 

 produces these effects chiefly through competition for food or oxygen, 

 but toxic substances in excreta also play a large part, and it is at 

 least possible that volume and space as such may be involved in some 

 instances (Allee, 1931, a: 118). 



There are instances of disoperation of bloodsucking insects which 

 carry fatal diseases and thus destroy their food supply, but all clear 

 cases are associated with human disturbance of natural communities. 

 However, Ricker (1932) has pointed out that, in certain ponds under 

 conditions that might well occur without man's interference, suckers 

 remove submerged vegetation which supports various aquatic inverte- 

 brates and produce a mud bottom in which only bloodworms (chiro- 

 nomid larvae) occur. The suckers thereby decrease the favorite food 

 of trout which pick a considerable part of it from the plants, and the 

 number of trout is decreased. This is a clear example of disoperation, 

 and Ricker points out that at the same time trout and suckers are to 

 some extent in direct competition for the same food (cf, Cahn, 1929) . 



COMPETITION 

 Nature and Correlation. In contrasting competition with other 

 coactions in preceding sections, it has already been defined in brief, 

 but a comprehensive treatment demands that the lines be drawn with 

 more exactness and in greater detail. The process may be defined 

 inclusively as a more or less active demand in excess of the immediate 

 supply of material or condition on the part of two or more organisms. 

 It may concern a particular object or a set of conditions; it may be 

 exhibited by as few as two individuals, by a vast family horde as with 

 many ungulates, and in communities of every possible size and com- 

 plexity. Its most striking manifestations are associated with crowd- 



