The trapping capability of Arthrobotrys oligospora and A. conoides (Hyphomycetales) against third stage larvae (L3) of Haemonchus contortus (Trichostrongylidae) was evaluated in an in vitro trial. Arthrobotrys oligospora showed a 35.87% and 25.71% trapping effectiveness against H. contortus infective larvae at 18 and 25°C, respectively; whereas the trapping capability of A. conoides was 92.17% and 90.40% at the same temperatures, respectively. Microscopic examination demonstrated that A. conoides spontaneously developed a large quantity of three-dimensional loops before the nematodes were added. Neither of the two species studied developed three-dimensional adhesive loops at 30°C, consequently no trapped nematode was observed. In a second trial, the trapping capability of A. conoides against H. contortus (L3) and second stage larvae (J2) of Nacobbus aberrans (Pratylenchidae), was evaluated at 25°C. The trapping capability shown by A. conoides was higher than 90% for both kinds of nematode. The possible use of A. conoides to control ovine haemonchosis is discussed.