Parasite induced changes in host behavior is considered adaptive if it provides a reproductive advantage to the parasite. The entomopathogenic fungi are a fascinating group of arthropod parasites that exhibit enormous diversity in terms of both host choice and reproductive strategy, some of which actively manipulate the behavior of their host as a means to increase reproductive success. Here we focus on anamorphs of the genus Torrubiella, namely Gibellula spp., which are all obligate pathogens of spiders that kill their hosts in locations suspiciously ideal for fungal reproduction and propagation. In a final, eerily purposeful act, hosts reliably spin a thin stratum of web on the under-surface of a leaf to which they secure themselves immediately before death. We provide both theoretical and empirical lines of evidence that this phenomenon represents an extended phenotype of parasite genes analogous to those observed in other taxonomically related parasite-host systems. We argue that observations of spiders killed by Gibellula sp. both in the field (in situ) and the laboratory (in vitro), as well as this species’ close phylogenetic relation to other fungal lineages believed or suspected to influence host behavior, are strong evidence for the presence of adaptive manipulation.