Some temperate wood-boring cerambycid beetles harbor intracellular gut yeasts believed to augment host nutrition. Thus far, gut yeasts isolated from Neotropical cerambycids do not appear to be vertically transmitted and may be members of an interacting guild. In this project we collected and processed cerambycid larvae, along with frass and wood samples, from branches severed from eight trees (four species) in the Brazil nut family. We used LSU rDNA sequence to assign preliminary identifications to 21 yeast strains from 45 isolates. Most yeasts were represented by one or two isolates, but Pichia guilliermondii and an undescribed species of Candida accounted for 42% of the isolates. Gut yeasts are not a random subset of yeasts in the environment: larval surfaces gave rise primarily to phylloplane species. We have never isolated the same yeast from both larval gut and frass, which suggests that the gut may selectively retain certain yeasts, or frass may be colonized subsequent to deposition. Larvae from branches cut during the dry season appear to host a complex community of gut microbes relative to larvae from branches cut during the rainy season. If gut yeasts do indeed provide nutritional benefits to their hosts, this heterogeneity may influence beetle seasonality.