Recently, biological systematic studies have contributed for understanding of evolutionary histories of living organisms. In this talk, I present how evolutionary histories are inferred from the phylogenetic relationships. Two case studies in the Cimicomorpha (Heteroptera) are presented: 1. Inferring ancestral character states of the plant bugs (Heteroptera: Miridae); 2. Revealing evolutionary history of the Cimicoidea based on correlated evolution between habitat selection and morphological characters (Heteroptera: Cimiciformes). Case I: The first comprehensive cladistic analysis of Miridae, the plant bugs, is presented based on analysis of 3935 base pairs of mitochondrial (16S, COI) and nuclear (18S, 28SD3) DNA for 91 taxa in seven subfamilies. Data were analyzed using maximum likelihood (ML), parsimony, and Bayesian inference (BI) phylogenetic frameworks. Divergence time estimates indicate that the radiation of the Miridae began in the Permian; most genus-level radiations within subfamilies began in the late Cretaceous, probably in response to the angiosperm radiation. Ancestral feeding state reconstructions based on Bayesian and parsimony inference were largely congruent and both reconstructed phytophagy as the ancestral state of the Miridae. Furthermore, the feeding habits of the common ancestors of Mirinae + Deraeocorinae, Bryocorinae + Cylapinae + Isometopinae + Orthotylinae, and the remaining taxa excluding Phylinae, were inferred as phytophagous. Therefore, at least three shifts from phytophagy or polyphagy to predation occurred within the Miridae. Case II: The diverse habitat types and discrete morphological characters of cimicoid species provide a unique opportunity to study correlated evolution. Phylogenetic relationships within Cimicoidea were determined using Bayesian analyses of molecular data, allowing the generation of testable hypotheses of correlated evolution. An investigation of the correlation between habitat selection and morphological characters revealed that a dead plant habitat was correlated with the filiform antennal type. Furthermore, molecular dating analysis was used to examine divergence times within the Cimicoidea. Transitions to live plants from dead plants for most cimicoid clades started right after the mid–Cretaceous, coinciding with the radiation of the angiosperms. Using contingency analyses, I determined that evolutionary changes in morphological characters were dependent on habitat selection. Based on these results, I propose evolutionary historical hypotheses for the Cimicoidea.