In the family Miridae (Hemiptera), females and males attract each other by means of sex pheromones. Among insects, these pheromones are characterized by a variety of chemical structures, including saturated and unsaturated, long- and short-chain esters, as well as unsaturated ketoaldehydes. The aim of this study was to assess the chemical emissions in Eccritotarsus catarinensis (Carvalho) and Eccritotarsus eichhorniae Henry to determine their similarity and their possible role in reproductive isolation mechanisms that led to speciation. Chemicals emitted by adults inserted in air-entrainment chambers were collected in absorbent tubes and were analyzed using gas chromatography–mass spectrometry (GC-MS). Results from the GC-MS library indicate that E. catarinensis females and E. eichhorniae males have chemical emissions that their conspecific and the same sex of the other species lack. Also, E. catarinensis males lack benzenebutanoic that the other sexes have, while E. eichhorniae males have 1,2,3,4-tetrahydro-6-(phenyl methyl) that other sexes lack. Further analysis using statistical approaches (e.g., cluster analysis, multidimensional scaling plot, and principal component ordination) indicated that cross-breeding pairs have similar chemical emissions in that E. eichhorniae females had similar chemical emissions to those of E. catarinensis males, while E. catarinensis females had similar chemical emissions to those of E. eichhorniae males. These unique differences in chemical emissions could be caused by the recently identified differences in the metathoracic scent glands and the antennae of the two Eccritotarsus species, and they may serve as a basis in explaining the interbreeding and mating incompatibilities reported in these two Eccritotarsus species.

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