Infections were carried out in the laboratory to determine the host range, specificity, and virulence of Steinernema rarum, S. feltiae, and Heterorhabditis bacteriophora that were isolated from different regions of Argentina. All insect orders showed a remarkable susceptibility to the three nematode species, showing mortality values higher than 66%, except for Anoplura. The mortality of the insects of agronomic interest was more than 90%. As for insects of sanitary importance, S. feltiae and S. rarum caused 60% of mortality, whereas H. bacteriophora caused 80%. The results fluctuated when considering the buccal apparatus function of the insects. Nematodes completed their cycle in anoplurans, orthopterans, lepidopterans, and hymenopterans, while the development varied in coleopterans, homopterans, hemipterans, and dipterans. S. rarum developed completely both in immature and adult, while S. feltiae and H. bacteriophora developed preferably in immature. The three isolates are capable of parasitizing a wide host range under laboratory conditions; H. bacteriophora is more virulent than the evaluated Steinernema spp. against Galleria mellonella larvae; the pathogenicity and specificity depend on the bioecological characteristics of nematodes and hosts.

La sensibilite du pou de tete, Pediculus humanus capitis, aux nematodes entomoparasites Steinernema rara, S. feltiae, Heterorhabditis bacteriophora (souches Oliva et Rio Negro) a ete evaluee. Tous ces nematodes (a l'exception de S. feltiae) tuent les adultes et les nymphes, mais non les oeufs. La souche Rio Negro de H. bacteriophora et S. rara se montrent bien plus agressives envers les adultes et les nymphes que les autres nematodes. H. bacteriophora souche Oliva est plus agressif envers les adultes. La penetration des larves infestantes a lieu apparemment par les spiracles et le diametre du corps des larves infestantes constituerait un facteur limitant. Le parasitisme du pou de tete par des nematodes entomoparasites est relate pour la premiere fois.

The effects of temperature and inoculum density on the biocontrol efficacy of Heterorhabditis bacteriophora were studied. Efficacy of infective juveniles from hermaphroditic females and amphimictic females were compared using Galleria mellonella as hosts. The infective juveniles were placed in contact with insects at concentrations of 2, 4, 8, 16 and 32 individuals per host. Temperatures varied between 12 degrees C and 36 degrees C at intervals of 2 degrees C. Temperature, concentration of infective juveniles and origin of juveniles had significant influences (p less than or equal to 0.01) on host mortality. Highest mortality was recorded at 26 degrees C. Infective juveniles of the hermaphrodites killed more G. mellonella than did those of the amphimictic females.