Interspecific competition was hypothesized to exist as a result of foraging byMonochamus titillatorFabricius in the sub-cortical region of loblolly pines attacked byDendroctonus frontalisZimmerman. The existence of the interaction was demonstrated experimentally; first by defining the distributional pattern ofD. frontalisprogeny adults in samples of bark in whichM. titillatorforaging was absent. Next, using data in which foraging occurred the observed number ofD. frontalisinside the foraged area was compared with the expected number if no foraging were present. The observed and expected values were demonstrated to come from different distributions which substantiated the existence of competition.The specifications for developing mathematical models of the competitive process included consideration of the extent and distribution ofM. titillatorforaging over the entire bole of the tree andD. frontalisdensity in the infested portion of the tree bole. The form of the data used in model development was appraised from the standpoint of providing the most realistic account of the process under consideration and the results of the use of unmanipulated data were compared with 2 separate types of manipulations commonly employed in the analysis of bark beetle populations.A series of nonlinear mathematical models based on unmanipulated data was developed which provides the expression of mortality resulting toD. frontalisas a consequence ofM. titillatorforaging as well as a survivorship model. These models include a definition of the following components: the relationship between the expected number ofD. frontalisin the area foraged byM. titillator[E(SPB¯1)] and the normalized tree bole (obtained by dividing the sample height, S.H., by the infested bole height, I.B.H.); the difference between observed number ofD. frontalisin the foraged area (SPB¯1) and E(SPB¯1)=∆(SPB¯1) and S.H./I.B.H.; the relationship between the area foraged byM. titillatorA¯1and S.H./I.B.H.; the relationship between ∆SPB¯1andA¯1, which is the mortality expression; and the relationship between (SPB¯1)/E(SPB¯1) andA¯1, which is the survivorship expression.The object of competition between the 2 species is the limited area of inner-bark necessary for development of both species. The form of the competitive process contains elements of both interference and exploitation.