As a result of monitoring of Hymenoptera species on the territory of the Republic of Moldova using artificial shelters (Fabre's nest with dry hollow stems of Phragmites and Reynoutria) and hand-collecting methods during 2024–2025, new data on the distribution of two alien species were obtained. A rare species has been discovered in the central part of the country - Isodontia mexicana de Saussure, 1867 (Hymenoptera: Sphecidae) in cardboard artificial shelters placed in an apple orchard and on an aromatic plant plantation. A detailed morphological description of the species is provided, including diagnostic characters of the adult, as well as data on life cycle, ecology and potential role as a pollinator and regulator of orthopteran populations. Furthermore, the current status of Tremex fuscicornis, Fabricius, 1787 (Hymenoptera: Siricidae) is clarified, with a female specimen collected by hand in a forest shelterbelt in the central region of the country. A detailed morphological description of the female is presented, including the structure of the head, thorax, abdomen, ovipositor and wings. The distribution of the species in Europe, its biology, trophic relationships with the symbiotic fungus Cerrena unicolor and host species (deciduous trees) were analyzed. It is shown that climate change (increasing average annual temperatures, increased drought frequency) creates favorable conditions for the naturalization and potential outbreak of T. fuscicornis as a secondary pest of weakened tree stands. Measures for monitoring and protecting plants have been proposed, including sanitary felling and the conservation of natural parasitoids – wasps of the genus Megarhyssa, Ashmead, 1858 and Ibalia, Latreille, 1802. Species of Isodontia mexicana has potential as a biological control agent against orthopteran pests and as a pollinator, whereas Tremex fuscicornis is a secondary forest pest causing damage to tree stands and timber.