Generalized phylogeny of Rhopalosomatidae showing currently confirmed host associations. The tree topology is based on Brothers (1999), Guidotti (1999), and unpublished molecular data (Blaschke et al., unpublished results). The information on the parasitoid-host-associations are based on Hood (1913), Gurney (1953), and Miller et al. (2019) for Rhopalosoma cf. nearcticum, Townes (1977) and Lohrmann et al. (2014) for O. banksii, Perkins (1908) for O. australiae, and the herein presented data for O. cf. testaceum. Townes (1977) mentioned Cycloptilum trigonipalpum (Mogoplistidae) as the potential host of O. testaceum, however, this association is not included here since the association is based only on the size of the wasp larva and the fact that no other Olixon species was known from Honduras at that time. Symbols: § Information on the biogeographic regions of the parasitoids are based on Lohrmann et al. (2020; table 1) and Bulbol et al. (2021) for Liosphex, Krogmann et al. (2009), Lohrmann et al. (2012), Lohrmann et al. (2020), and Bulbol et al. (2023) for Olixon, Lohrmann (2011) and Lohrmann et al. (2020; table 1) for Paniscomima, Townes (1977), Miller et al. (2019), and Lohrmann et al. (2019) for Rhopalosoma, and Lohrmann et al. (2020) for Cretolixon and Eorhopalosoma. # The classification of the hosts follows Cigliano et al. (2023). * The herein published data suggests at least six species in the O. testaceum species group. **Miller et al. (2019) discovered that the nearctic species R. nearcticum actually consists of at least two distinct genetic lineages, i.e., R. ? nearcticum 1 and R. ? nearcticum 2.