Abstract: Host searching for Tiphia sp. by T. popilliavora and two geographical strains of T. vernalis were compared by Y olfactometer and field experiment.
It was found that three strains of the 2 Tiphia species could not perceive the existence of host white grub third instar larvae per se, but T. vernalis
was more sensitive to host frass than T. popilliavora and odor collected from host larvae and frass was more attractive to Tiphia spp. than frass odor only. The wasps could not tell host from nonhost larvae within the distance of the sealed channel that was filled with sandy soil, but could orient to their host's box when there were host frass. When larvae odor of host and nonhost coexisted, T. vernalis could locate its host but T. popilliavora hesitated, apparently confused by non-host larvae odor. 67.5% of the test population of T. vernalis geographical strains A-NC dug into under grass channel and find host out, no matter there was a mouth existed in the cage or not, but T. vernalis geographical strains of CH-SD test channel only through the mouth. Frass placed around the mouth could be the clue that attracts wasps to dig into host channel, nevertheless, frass sprinkled randomly on grass lacked the function of host location indicator.