This study is the first to investigate the ingestion of microplastics (MPs), plasticizers, additives, and particles of micro-litter Simulium equinum and Simulium ornatum, were collected in two rivers in Central Italy, the Mignone and the Treja. Small microplastics (SMPs, 90%. Differences in the abundances of the SMPs and APFs ingested by the two species under exam were statistically significant. Additives and plasticizers can be specific to a particular polymer; thus, these compounds can be proxies for the presence of plastic polymers in the environment.