Maternal care thwarts parasitoids in the invasive brown widow spider ().

Maternal care can maximize offspring survival and may contribute to the establishment success of invasive species. The brown widow spider, , is a successful invader worldwide. Here, we investigated the role of maternal care in enhancing its success. We compared the defence mechanisms of the invasive with those of another widow spider native to the Negev desert, , against an egg sac parasitoid wasp. Both spider species exhibited guarding behaviours following exposure to wasps; however, only efficiently evaded and successfully killed the parasitoid. Accordingly, its egg sacs were parasitized less frequently than those of . Next, we evaluated the defensive role of the silk spike-like structures on egg sacs. When spikes were removed from half of the egg sac surface, the wasps laid more eggs on the spike-free side. In an additional experiment, females increased spike density on subsequent egg sacs after exposure to the parasitoid. We showed that employs both behavioural defences and modifications to the egg sac structure to protect against the parasitoid. These defences may provide with an advantage over native species in its invasive range, potentially contributing to its invasion success.