The process of excitation energy migration (EEM) in conjugated polymers, which is relevant both for light emitting diodes and laser applications, is probed by doping the blue light emitting methyl-substituted ladder-type poly(para-phenylene) with small concentrations of a highly fluorescent pi-conjugated macromolecule. The experimentally attained temperature and concentration dependence of the steady state photoluminescence is modeled and discussed by means of a two-step EEM process: (1) a thermally activated migration within the host and (2) transfer from the host to the guest. In particular we show that a Forster-type mechanism alone cannot account for the experimental facts in such a guest host system.