Existence of infective juveniles in the offspring of first- and second-generation adults of Steinernema rarum (OLI strain): evaluation of their virulence.

Descriptions of the life cycle of the genus Steinernema do not consider the production of infective juveniles (IJs) by the first-generation developed within the insect host when more than one generation develops. We demonstrated IJ production by first- and second-generation adults of Steinernema rarum (OLI strain), evaluated their virulence and compared virulence and morphometric characters between the two IJ forms. Our results demonstrated not only the presence of IJs in the offspring of first- and second-generation adults but also a greater virulence of first-generation IJs. Both types of IJs also differed in five morphometric characters. According to our results, a population of IJs emerging from a host cadaver has individuals of two generations with different characteristics; hence, they should not be considered the same. These generational differences may be exploited, for example, for biocontrol purposes, by using a specific generation of IJs for inoculative release.