Resource exploitation and competitive interactions

The degree of exploitation of a resource may depend on a variety of traits of the resource as well as those of the insect exploiter. 

Individuals that participate in large aggregations per unit of resource may lower their individual fitness owing to local resource exhaustion or deterioration. Under crowded conditions, an individual may exercise one of three options stay put and attempt to obtain sufficient resource from the present unit, enter diapause, or attempt to locate other resource units and risk mortality during dispersal. 

The portion of the population which remains in an overcrowded habitat may necessarily engage in competition, that is, the active demand by two or more individuals for a common resource (Wilson 1975). Competition has been broadly classifled into two processes interference and exploitation (Park, 1954). 

Interference competition embraces any activity which directly or indirectly limits a competitor s access to a resource (Miller, 1967). Indirect interference invariably involves a form of chemical communication, or signal, which is effective in the owner s absence. Direct interference includes a range of interactions such as territoriality, dominance, physiological or physical suppression, and cannibalism. Exploitation is the joint utilization of a limited resource once access has been gained (Miller, 1967). Thus, rather than deal with other individuals, an exploiter deals exclusively with available resources and is successful only through competitive ability. Nicholson (1954) proposed a comparable, but not identical, distinction between modes of competition by designating contest and scramble competition, terms which relate to interference and exploitation competition, respectively. 

Well-documented studies of interference competition exist. Elimination of supernumerary larval parasitoids by physical attack of conspecifics is a dramatic case of direct interference by a competitor (Salt, 1961). Other examples include physical defense of territories by Pogonomyrmex harvester ants and Trigona bee species, and cannibalism in Tribolium beetles (Young, 1970) (see Section 11.5). Examples of indirect interference competition via chemical mediators have been found increasingly over the past decade (Prokopy, 1981a see also Section 11.5). 

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