The closer the better: Sensory tools and host-association in blood-sucking insects

[Display omitted] •Chemo-sensilla are the most abundant on the antennae of lice, bed bugs, kissing bugs and mosquitoes.•ORs, IRs, GRs, OBPs and CSPs are more abundant than TRPs and PPKs in kissing bugs and mosquitoes.•High degrees of association with hosts are correlated with smaller numbers of sensilla and genes.•Blood feeders with a lower degree of association with the host present higher diversity of sensilla. Many hematophagous insects acquire medical and veterinary relevance because they transmit disease causing pathogens to humans. Hematophagy is only fulfilled once a blood feeder successfully locates a vertebrate host by means of fine sensory systems. In nature, blood-sucking insects can exploit environments with differential association with their hosts. Given the relevance of the sensory systems during host searching, we review the current state of knowledge of the sensory machinery of four blood-sucking insects: human lice, bed bugs, kissing bugs and mosquitoes. Each one is representative of highly anthropophilic behaviours and a different degree of association with human hosts. We compare the number, arrangement and functional type of cuticular sensory structures dispersed on the main sensory organs. We also compare the genetic machinery potentially involved in the detection of host stimuli. Finally, we discuss the sensory diversity of the insects studied here.