A Phenomenon: What Are the Minuscule Grey Moths Abundant in the Dry Season in the Tropical Dry Forests of the Pacific Coast of Honduras?

Simple Summary: Understanding the diversity, distribution, and ecological roles of leaf-mining Lepidoptera across different biomes is both intriguing and important for advancing our knowledge of biodiversity and ecosystem functioning. Despite extensive studies on leaf-mining Nepticulidae in tropical environments, no one had previously explored trapping in completely dry deciduous forests, especially during the peak of the dry season when trees are bare and even grass is dried out. This paper reveals an unexpected and astonishing abundance of minuscule plant-mining Nepticulidae moths in such dry deciduous forests. Our study ecoregion, the tropical dry forests of Honduras, includes the Pacific coastal lowlands and premontane areas extending into low-altitude regions further inland, known for their rich biodiversity and high levels of endemism. In these tropical dry forests, we identified five species of pygmy moths belonging to the genus Acalyptris Meyrick, including three new species. These moths are characterized by their distinctive grey coloration and exceptionally small size, classified as "extremely small". Despite their similarities, they exhibit significant differences in genital structures and molecular profiles, indicating distinct species groups. Our research also uncovered novel atypical morphological traits in Nepticulidae from this ecoregion. These findings highlight the unique and highly specific nature of the Nepticulidae fauna in tropical dry forests. A key question arises regarding the presence of Nepticulidae adults during the dry season: could they be mining plant bark instead of leaves? This paper aims to stimulate further exploration of micromoths in other tropical dry forests, which, despite their limited and fragmented distribution, are found not only in Central America but also in other regions worldwide. Our investigation centered on the tropical dry forests along the Pacific coast of Honduras, aiming to elucidate the presence and abundance of minuscule grey moths during the dry season. Through specimen dissections and the taxonomic identification of the collected material, we have described three new species: Acalyptris podenasi sp. nov., A. palpiformis sp. nov., and A. tortoris sp. nov. Additionally, we documented two species previously known from neighboring countries, A. lascuevella Puplesis & Robinson and A. basicornis Remeikis & Stonis. The females of A. lascuevella were previously unknown and are documented here for the first time. Morphological examinations were complemented by DNA barcoding, particularly highlighting variation in A. lascuevella. The paper's primary significance lies not only in the description of new species but also in uncovering their taxonomic, morphological, and molecular importance. We found that these species are unique and indicative of the previously unstudied dry forests as a distinct ecosystem. Our findings revealed several novel atypical morphological traits within the studied Nepticulidae, including unusually large signum cells in the female genitalia, a dorso-ventrally divided uncus, and asymmetrical valvae in the male genitalia. These discoveries underscore the morphological diversity of Acalyptris Meyrick and their significance in evolutionary biology. Consequently, the paper addresses a previously unknown phenomenon of the occurrence and astonishing abundance of minuscule plant-mining micromoths in dry deciduous forests during the peak of the dry season. We hope that this paper will encourage Lepidoptera taxonomists to explore micromoths in other tropical dry forests, which, while limited in distribution, hold global importance. The paper is extensively illustrated with photographs of Acalyptris adults and their genitalia, along with maps, habitats, and molecular phylogenetic trees. [ABSTRACT FROM AUTHOR]