Other eicosanoids released by T. cruzi may also contribute to vertebrate parasite infection. Therefore, the abundance and types of lipids available to T. cruzi during vector infection will affect its ability to synthesize eicosanoids, which can have a direct impact on both the parasite itself and on the vector host. This in turn can affect the outcome of the vector-parasite interaction. In support of this concept, it has recently been shown that the production of eicosanoids during T. cruzi infections of mammalian hosts has an effect on parasite burden, and this may also be true during Euphorbia factor L3 triatomine infections. In humans, dietary preferences and nutritional composition have been shown to influence gut microbial metabolism and, correlatively, health. Similarly, a number of B vitamins, namely nicotinamide, thiamin, pyridoxine, riboflavin, p-aminobenzoic acid and biotin, were shown to be essential to R. prolixus molting and were associated with symbionts. Choline and folic acid are B vitamins that are essential to T. cruzi growth in minimal medium. In contrast, p-aminobenzoic acid, biotin and pyridoxine were not essential to T. cruzi. Folates are conjugated pterines that contain p-aminobenzoic acid and Lglutamates connected to the methyl group at position 6 of the pteridine ring system. The activity of extracellular folic acid is regulated by a folic acid synthase. Many factors may be critical to promoting Salvianolic-acid-B metabolic diversification among triatomine species, as described above. One determinant of the gut chemical composition is the intestinal microbiota. A recent study showed that the chemical composition of mouse feces is highly disturbed by killing the intestinal microbiota. The gut microbiota of triatomines was recently studied by our group. The results showed that the composition of bacterial microbiota varies among triatomine species but is conserved among the individuals of one species, regardless of their geographic origin. In contrast, insect vector competence may vary with geographic location and may affect T. cruzi epidemiology. The relative regularity of microbiota in the triatomine guts regardless of the geographic location of a given vector species is not surprising, because the host determinants were shown to be essential factors of microbiota composition. In addition, the vast majority of the bacterial community was composed of endosymbiotic species as determined by DGGE. In that sense, one should consider bacterial microbiota as a rather constant part of the vector system that may affect T. cruzi in situ. Another potential determinant of the metabolic changes observed here is the digestive process of each triatomine species. Although knowledge of triatomine physiology is fragmented among insect vector species, R. prolixus digestion has been studied for many years, and the activities of several cysteine and/or aspartic proteinases have been identified in the posterior midgut. More recent studies have demonstrated the presence of genes encoding cathepsins B and L in the midgut of R. prolixus and T. infestans, respectively. In addition to differences in digestive enzymes in the gut, in P. megistus, T. infestans and R. prolixus defecation is stimulated by blood ingestion, which immediately induces the discharge of a high amount of feces after feeding. Therefore, differences in the timing and volume of this excretion between triatomine species may affect the metabolic composition of feces. In reality, all of the factors mentioned above will contribute to the chemical composition of the insect gut, and dissecting their individual contributions will be a challenge worth undertaking.