Keep calm and carry on: bites from Trichonephila clavata are unlikely and cause minimal discomfort.

Arachnophobia is a widespread phenomenon, despite the fact that the vast majority of spiders pose no meaningful threat to people. The introduction and spread of an invasive spider (Trichonephila clavata L. Koch, 1878) to the United States has prompted questions about whether it should be considered dangerous. These questions are particularly relevant because the spider is large, builds webs on and near human structures, and has been documented to consume small vertebrate prey. To understand the realistic threat this species represents, we examined spider-human interactions in the field with escalating levels of contact intensity. During these interactions, spiders primarily moved to avoid human contact, and bites were incredibly rare, mainly occurring when spiders were forcibly restrained. To assess the medical significance of a bite by T. clavata, we conducted what we believe to be the first controlled study of spider bites. Spiders were induced to bite volunteers under controlled laboratory conditions while supervised by medical staff. Subjects who were bitten reported reliably low levels of pain and only localized physical symptoms (eg redness and swelling) that attenuated quickly. It is clear that this spider is unlikely to bite someone who encounters it in nature, and the symptoms are minor and fleeting in the event of a bite. Although T. clavata is spreading quickly in the United States, the risk of its bite or resulting symptoms should not be cause for fear.