The harlequin ladybird (Harmonia axyridis) was introduced in numerous countries around the world as a biological control agent but nowadays it is considered as a pest itself. It is a highly invasive species that has negative impacts on native biodiversity, may affect some crops, and causes a nuisance to humans. Despite its relevance worldwide, the invasion by H. axyridis in South America has received little attention. Here we used a citizen science approach to study the distribution of H. axyridis in Argentina where the species was intentionally introduced in 1986. We also informally tested and evaluated the preferences for different methods for reporting records: iNaturalist website, Google form, email, WhatsApp, and Facebook. Most records were reported through WhatsApp and iNaturalist. We found that H. axyridis is widely distributed in Argentina but there are large gaps, particularly in arid regions. The invasion seems to be recent in the south of the country. Citizen science is a valuable tool for mapping invasive alien species in a large country like Argentina, and will help to monitor the continuous expansion of H. axyridis.

丑角瓢虫（Harmonia axyridis）作为生物防治剂被引入世界许多国家，但如今它被认为是一种有害生物。它是一种高度入侵的物种，会对本地生物多样性产生负面影响，可能会影响某些作物，并对人类造成滋扰。尽管它在世界范围内具有重要意义，但在南美洲，木槿H. axyridis的入侵却鲜有受到关注。在这里，我们使用了一种公民科学方法来研究轴心菌的分布在1986年有意引入该物种的阿根廷。我们还非正式地测试和评估了各种报告记录方法的偏好：iNaturalist网站，Google表单，电子邮件，WhatsApp和Facebook。大多数记录是通过WhatsApp和iNaturalist报告的。我们发现，轴心线虫在阿根廷分布广泛，但差距很大，尤其是在干旱地区。入侵似乎是该国南部最近的事。公民科学是在阿根廷这样的大国中绘制外来入侵物种图谱的宝贵工具，并将有助于监测木虱的持续扩张。