Characterizing Antistrophus gall wasps (Hymenoptera: Cynipoidea: Aulacideini) in crop silflower fields (Asteraceae: Heliantheae: Silphium integrifolium complex)

A large barrier to the development of novel crops is the identification and control of pests. In the case of crop silflower (Asteraceae: Heliantheae: Silphium integrifolium complex), recent studies have indicated the pest potential of gall wasps in the genus Antistrophus Walsh, 1869 (Hymenoptera: Cynipoidea: Aulacideini). After observing high abundance of gall wasps in silflower fields at The Land Institute (Salina, Kansas, USA), we sampled silflower to identify the Antistrophus species present and to improve understanding of secondary plant modifications to their host plants (alterations to the host plant beyond the gall itself). Our survey revealed the presence of four gall wasp species: A. bicolor Gillette, 1891; A. silphii Gillette, 1891; and two additional undescribed species. To enable recognition of these species, we provide descriptions of galls, a key to the adult female Antistrophus species from crop silflower, and initial interpretations of how each species may impact host plant health. Our findings elucidate questions of taxonomy in the genus Silphium L., illustrate the need for further work on their endophytic insect communities, and set the stage for further evaluation of pest potential in Antistrophus.