Multiple foundresses and multiple hosts: The influences of kinship and host quality on group reproduction in a quasi‐social parasitoid

For most foraging parasitoids, it is disadvantageous to share a host. In the genus Sclerodermus females can benefit from being among groups of foundresses, which cooperate in brood production over several weeks, but intra‐group conflicts also arise. We provided groups of females, with varying degrees of relatedness, with two hosts, in varying host size combinations, and observed behaviours and performance. Foundress death, likely caused by host defensive behaviour, was common during the initial phase, especially when foundresses were closer kin. At least one host was always oviposited on and in 60% of cases both were. When host size differed and only one was oviposited on, there was no preference for larger hosts. Oviposition was most rapid when both hosts were large and females were non‐siblings. Offspring production was greatest when broods developed on two large hosts and was not influenced by foundress kinship. Aggregation of foundresses across hosts may be promoted by variation in host size and by kinship. Foundresses were most commonly observed alone on a host but also shared hosts; all females on a single host was uncommon. Foundresses commonly moved between the hosts, most frequently when both hosts were large. Movement was not, overall, influenced by kinship. Overall, the behavioural repertoire of Sclerodermus indicates that they are able to assess and exploit locally available alternative reproductive opportunities and may attune some of their decisions according to inter‐group relatedness.