Abstract
Chalcidoidea are incredibly speciose and biologically diverse, which reflects the vast range of hosts, habitats and conditions they experience. The diversity of habitats in which hosts are located may be just as important as host diversity as a driver of diversification. Females attack hosts in both exposed and concealed situations, including within leafmines, galls, soil, wood cavities, and inside other hosts, and even under water, as just a few examples. This chapter explores their broad diversity of behaviors and attempts to synthesize information that crosses the families' boundaries within Chalcidoidea in an integrated look into the intricate world of these tiny wasps.