Before Linnaeus published the Systema Naturae, in which introduced the modern species concept, a huge amount of information on ecology, behaviour and diversity of many animals had been accumulated. This information, often extremely detailed, suffers from the lack of the assignation of the studied organisms to their modern specific names. Here, we examine in detail the works of Antonio Vallisneri (1661-1730), one of the most important figures of early experimental entomology in Italy. We analyse the ecological and ethological contributions of Vallisneri, as well as those that Diacinto Cestoni (1637-1718), another Italian naturalist, sent to Vallisneri, to the knowledge of parasitoid, predatory and gall-making wasps (Hymenoptera), by studying the Saggio de' Dialoghi sopra la curiosa origine di molti Insetti and the Quaderni di Osservazioni I-III, trying to assign current taxonomy to the observed insects based on eco-ethological and morphological descriptions. Valuable data have been found in the analysed works on taxonomically diverse ecological webs involving wasps. Information regarded a variety of hymenopteran parasitoids of other Hymenoptera, dipteran parasitoids of Hymenoptera, coleopteran parasitoids of Hymenoptera, and hymenopteran parasitoids associated with non-hymenopteran hosts. Overall, about 20 wasp genera could have been objects of Vallisneri and Cestoni observations, which include the first detailed ecological and ethological data on many of them. Detailed re-examinations of ancient studies may contribute to our knowledge on biodiversity by providing historical distribution data as well as unveiling trophic interactions that may have been modified due to biodiversity loss in the last century.