Municipal wastewater effluents (MWWEs) contain antimicrobials and other contaminants that can alter the microbiomes of exposed aquatic animals, potentially negatively impacting host health. Contaminants and nutrients from MWWEs may be transferred across the aquatic - riparian boundary by aquatic insects, potentially altering the microbiomes of both prey and consumers. We evaluated host microbiome compositions of several taxa of freshwater larval and adult insects, and riparian spiders at sites upstream and downstream of three wastewater treatment plants. Host microbiome compositions were analyzed by sequencing the 16S rRNA gene and MWWE exposure was assessed using stable carbon (δ