To give a concrete aspect of structure, topography and function of the different nervous systems of the Triatominae, we begin this study with a description of the senso-motor system. As the first part we choose the study of the brain and its nerves. The external form of the brain is conditioned by the anatomy and morphology of the head. The brain is situated in the posterior part of the head beneath and behind the ocelli. Is caracterized by the reduction of its longitudinal extension and, by this, the connectives between Syncerebrum and Gnathocerebrum are extremely short, but large, and the third commissure is included in the mass of the mandibular segment of the Gnatocerebrum. The optical masses are of the typical form, also the optical commissure. The Central Corps is volumous and is directly linked with the majority of the centres of the Protocerebrum and Deutocerebrum. The Pedunculated Corps has only one glomerulus that looks like a pedunculated mushroom without any signal of the formation of o calyx, found in ants and other more evoluated insects. Beneeth the central Corps, the extremities of the pedunculus disintegrate and form a number of claviform annexes like in the primitive Machilidae. The Deutocerebrum is caracterized by volumous antennal centre, composed by nummerous little glomerulus in peripherical situation. The Tritocerebrum is very reduced and has in its anterior part two very short frontal connectives and, by this, the frontal ganglion lies near the Tritocerebrum. The compact mass of the Gnathocerebrum shows its composition by three pairs of ganglions only by observation of series of preparations. With exception of the Lobi optici, 8 pair nerves and 3 impair nerves come from the brain: From the Protocerebrum: the nerves of the ocelli and the nerve of the corpus allatum. From the Deutocerebrum: the nerves of the antennae and those of the pharynx. From the Tritocerebrum: the nerves of the labrum and, by the frontal ganglion, the Nervus recurrens and the nerve of pharyngeal muscles. From the Gnathocerebrum: the nerves of the amndibulae, maxillae, labium and of the salivary glands.