Blood sucking arthropods are disease vectors worldwide. Despite the role of arthropod-blood feeding on pathogen acquisiton and spread, the molecular mechanisms by which a blood meal is handled by such organisms remain unknown. Rhodnius prolixus, the vector of  Chagas disease, ingests a huge amount of blood. The effect of one blood meal component, linoleic acid on the activation of intracellular signaling pathways is under investigation in our laboratory. We first evaluated mitogen activated protein kinase (MAPK) pathway. Our results show that gut strech itself is solely able to induce the expression of MAPK, as probed by ERK antibodies detected using a polyclonal antibody raised against the C-terminal portion of rat origin. Furthermore, the phosphorylation of ERK was demonstrated by monoclonal antibodies against the phosphorylated Tyr-204 of ERK of human origin. Curiously, when the blood meal included 200 mM of linoleic acid, a higher level of phosphorylation was noticed. However, when calcium or heme were included in the meal, in presence of linoleic acid, the phosphorylation but not the expression of ERK was abolished. The role of calcium and heme-mediated linoleic acid peroxidation (quasi-lipoxygenase activity) was next tested. Inclusion of linoleic acid, calcium and heme restored ERK phosphorylation. This result suggest that a product of quasi-lipoxygenase activity counteracts calcium and heme-mediated suppression of ERK phosphorylation. Identification of such molecule and its presence on a complete blood meal, as well as the mapping of intracellular proteins phosphorylated by such pathway, will be next evaluated.