Delayed identification of long-overlooked Aedes (Aedimorphus) vexans in Tahiti Island, French Polynesia

Aedes (Aedimorphus) vexans (Meigen, 1830) is a globally distributed mosquito species commonly associated with temporary flooded habitats, including those in the South Pacific region. While its presence has been documented in several Pacific archipelagos, its occurrence on Tahiti island had remained unconfirmed. A retrospective examination of historical mosquito collections held at the Institut de Recherche pour le Developpement (IRD, France) and the Institut Louis Malarde (ILM, Tahiti) revealed evidence of Ae. vexans on Tahiti dating back as early as 1993. This historical detection was corroborated by targeted field surveys conducted between 2023 and 2025, which confirmed the species presence at multiple sites, particularly in the southern part of the island. To support these observations, COI gene sequences from newly collected specimens were analyzed alongside reference Ae. vexans sequences from GenBank. The Tahitian specimens fall unambiguously within the Pacific clade of Ae. vexans and show no genetic divergence that would support their assignment to Ae. nocturnus or Ae. nipponii. Similarly, sequences published under these names in GenBank do not form distinct lineages within Ae. vexans. This study provides the first confirmed record of Ae. vexans on Tahiti, based on both morphological identification and molecular evidence. The findings underscore the need to integrate molecular tools into entomological monitoring to improve species detection and prevent misidentifications in island environments where vector diversity is often underestimated.