Neuropeptides and protein hormones constitute a very important group of signaling molecules, regulating central physiological processes such as reproduction, development, and behavior. Using a bioinformatics approach, we screened the recently sequenced genome of the parasitic wasp, Nasonia vitripennis, for the presence of these signaling molecules and annotated 30 precursor genes encoding 51 different mature neuropeptides or protein hormones. Twenty-four of the predicted mature Nasonia neuropeptides could be experimentally confirmed by mass spectrometry. We also discovered a completely novel neuropeptide gene in Nasonia, coding for peptides containing the C-terminal sequence RYamide. This gene has orthologs in nearly all arthropods with a sequenced genome, and its expression in mosquitoes was confirmed by mass spectrometry. No precursor could be identified for N-terminally extended FMRFamides, even though their putative G protein coupled receptor (GPCR) is present in the Nasonia genome. Neither the precursor nor the putative receptor could be identified for allatostatin-B, capa, the glycoprotein hormones GPA2/GPB5, kinin, proctolin, sex peptide, and sulfakinin, arguing that these signaling systems are truly absent in the wasp. Also, antidiuretic factors, allatotropin, and NPLP-like precursors are missing in Nasonia, but here the receptors have not been identified in any insect, so far. Nasonia (Hymenoptera) has the lowest number of neuropeptide precursor genes compared to Drosophila melanogaster, Aedes aegypti (both Diptera), Bombyx mori (Lepidoptera), Tribolium castaneum (Coleoptera), Apis mellifera (Hymenoptera), and Acyrthosiphon pisum (Hemiptera). This lower number of neuropeptide genes might be related to Nasonia's parasitic life.