Worldwide Web: High Venom Potency and Ability to Optimize Venom Usage Make the Globally Invasive Noble False Widow Spider (Thorell, 1875) (Theridiidae) Highly Competitive against Native European Spiders Sharing the Same Habitats.

Venom compositions include complex mixtures of toxic proteins that evolved to immobilize/dissuade organisms by disrupting biological functions. Venom production is metabolically expensive, and parsimonious use is expected, as suggested by the venom optimisation hypothesis. The decision-making capacity to regulate venom usage has never been demonstrated for the globally invasive Noble false widow (Thorell, 1875) (Theridiidae). Here, we investigated variations of venom quantities available in a wild population of and prey choice depending on venom availability. To partially determine their competitiveness, we compared their attack rate success, median effective dose (ED) and lethal dose (LD), with four sympatric synanthropic species: the lace webbed spider , the giant house spider , the missing sector orb-weaver , and the cellar spider . We show that regulates its venom usage based on availability, and its venom is up to 230-fold (0.56 mg/kg) more potent than native spiders. The high potency of venom and its ability to optimize its usage make this species highly competitive against native European spiders sharing the same habitats.