An infected bovine-baited trap was utilised in summer 1994 to catch possible intermediate hosts of S. labiatopapillosa in northeastern Italy. Collections were made for 21 nights from 8.00 p.m. to 6.00 a.m. every 2 h and, after 12 September, every 30 min. Among the 16,159 mosquitoes sampled, 11,052 were freshly blood-fed. Most of the unfed females and a representative sample of those which had fed were identified as follows: Culex pipiens, Aedes caspius, A. vexans, Culiseta annulata, Anopheles maculipennis s.l., A. claviger and Coquillettidia richiardii. In spite of having the highest relative density, C. pipiens is the species which fed the least frequently and showed lower susceptibility and efficiency. The 2 Aedes species appear to act as vectors, particularly A. caspius, which proved to be the most efficient vector (K.I. = 0.8). A. claviger and A. maculipennis contribute to S. labiatopapillosa transmission, but their scarce presence reduces their epidemiological relevance. The other species identified showed a complete refractoriness to the infection. The risks for veterinary and medical health are discussed.