Hidden in plain sight: discovery of sand flies in Singapore and description of four species new to science.

BACKGROUND: Phlebotomine sand flies (Diptera: Psychodidae) are tiny, blood-sucking insects that are of significant public and veterinary health importance for their role in the transmission of Leishmania parasites, bacteria, and arboviruses. Although sand flies have been documented in most Southeast Asian countries, there are no published records confirming their presence in Singapore. Here, we present this fauna with descriptions of new species. METHODS: Sand fly species identification was confirmed using an integrative taxonomic approach that combines morphological analysis with DNA barcoding of the mitochondrial cytochrome b (cytb) and cytochrome c oxidase subunit I (COI) genes. RESULTS: We identified eight sand fly species, including four newly described species: Phlebotomus seowpohi n. sp., Sergentomyia leechingae n. sp., Sergentomyia gubleri n. sp., and Sergentomyia retrocalcarae n. sp. Phylogenetic analyses suggest that the new Phlebotomus species, belonging to subgenus Euphlebotomus, is closely related to Phlebotomus argentipes, an important vector of Leishmania donovani from the South Asian region. CONCLUSIONS: The potential risk of leishmaniasis in Singapore is compounded by the recent detection of antibodies to Leishmania infantum in local free-roaming dogs. Therefore, continuous monitoring is essential to assess and manage the risk of disease agent transmission, support the development of an early warning system, and enable timely and targeted public health interventions. The findings of this study contribute to the global knowledge on sand flies and enhance our understanding of local fauna diversity and distribution.