Maternal care thwarts parasitoids in the invasive brown widow spider ( <i>Latrodectus geometricus</i> )

Maternal care can maximize offspring survival and may contribute to the establishment success of invasive species. The brown widow spider, <i>Latrodectus geometricus</i>, 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 <i>L. geometricus</i> with those of another widow spider native to the Negev desert, <i>Latrodectus pallidus</i>, against an egg sac parasitoid wasp. Both spider species exhibited guarding behaviours following exposure to wasps; however, only <i>L. geometricus</i> efficiently evaded and successfully killed the parasitoid. Accordingly, its egg sacs were parasitized less frequently than those of <i>L. pallidus</i>. Next, we evaluated the defensive role of the silk spike-like structures on <i>L. geometricus</i> 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, <i>L. geometricus</i> females increased spike density on subsequent egg sacs after exposure to the parasitoid. We showed that <i>L. geometricus</i> employs both behavioural defences and modifications to the egg sac structure to protect against the parasitoid. These defences may provide <i>L. geometricus</i> with an advantage over native species in its invasive range, potentially contributing to its invasion success.