Ribosome-inactivating proteins (RIPs) are rRNA N-glycosylases (EC 3.2.2.22) that depurinate an adenine residue from the conserved alpha-sarcin/ricin loop in rRNA, blocking protein synthesis. In previous research, we demonstrated that whiteflies from the Aleyrodidae family (e.g., Bemisia tabaci), mosquitoes from the Culicinae subfamily (e.g., Aedes aegypti), and flies of Sciaroidea superfamily (e.g., Contarinia nasturtii) acquired these genes via three independent horizontal gene transfer events. The temporal expression profiles analyzed in mosquitoes and flies are consistent with the expected for immune effector molecules of insects. Notably, in A. aegypti, we found that these genes contribute to immunity. In whiteflies, codon analysis suggests that RIP genes have evolved under the influence of natural selection. Public transcriptomic experiments have shown that these genes are expressed in the adult stage of B. tabaci. Despite computational findings supporting RIP genes functionality in whiteflies, no experimental studies have been conducted. Furthermore, there is currently no publicly available RNA-seq data evaluating gene expression throughout ontogeny in the Aleyrodidae family. In this work, we experimentally demonstrated the presence of these foreign genes in the genome of Trialeurodes vaporariorum. We quantified their expression across the life cycle stages of this species and analyzed their untranslated regions. The results obtained contribute to a deeper understanding of the biological roles that these ribotoxin encoding genes may play in whiteflies and other insects.