The monograph treats 29 species of leaf-mining pygmy moths (Insecta, Lepidoptera, Nepticulidae) discovered in the northern Andean bush and grass páramo and the central Andean puna at altitudes above 3700 m. They represent the world's highest-altitudinal Nepticulidae fauna known. The height record belongs to Stigmella nivea sp. nov. from Peru collected at an elevation of 4700 m. Except for one species, all belong to Stigmella Schrank. Twenty-two of the species recorded are new and are named and described in the current paper: Stigmella paramica Diškus & Stonis, sp. nov.; S. lachemillae Diškus & Stonis, sp. nov.; S. gynoxyphaga Diškus & Stonis, sp. nov.; S. calceolariae Diškus & Stonis, sp. nov.; S. rigida Diškus & Stonis, sp. nov.; S. altiplanica Diškus & Stonis, sp. nov.; S. robusta Remeikis & Stonis, sp. nov.; S. pseudorobusta Remeikis & Stonis, sp. nov.; S. auriargentata Remeikis & Stonis, sp. nov.; S. altimontana Remeikis & Stonis, sp. nov.; S. pandora Remeikis & Stonis, sp. nov.; S. ampla Diškus & Stonis, sp. nov.; S. evanida Diškus & Stonis, sp. nov.; S. mustelina Remeikis & Stonis, sp. nov.; S. angusta Diškus & Stonis, sp. nov.; S. alticosma Remeikis & Stonis, sp. nov.; S. nivea Remeikis & Stonis, sp. nov.; S. kristenseni Diškus & Stonis, sp. nov.; S. lobata Remeikis & Stonis, sp. nov.; S. ageratinae Diškus & Stonis, sp. nov.; S. clinopodiella Diškus & Stonis, sp. nov.; and S. calceolarifoliae Diškus & Stonis, sp. nov. Some of these species are leaf-miners on Asteraceae (Pentacalia, Baccharis, Gynoxys, and Ageratina plants), Calceolariaceae (Calceolaria), Lamiaceae (Clinopodium), and Rosaceae (Lachemilla). Twenty species are known only from adults with no data on their biology and host-plants. In addition, we present data and discuss recently discovered nepticulid taxa associated with Polylepis forests that is the natural vegetation in much of the High Andes. All High-Andean Stigmella species treated are illustrated with photographs of the adults and genitalia, distribution maps, including some with photographs of the leaf-mines and habitats.

Seven new species of Tischeriidae are described from the Neotropics: Astrotischeria jociui Diškus & Stonis, sp. nov. (feeding on Wissadula excelsior (Cav.) C. Presl., Malvaceae), A. atlantica Diškus & Stonis, sp. nov. (feeding on Baccharis spicata (Lam.) Baill., Asteraceae), A. cornuata Diškus & Stonis, sp. nov. (host plant unknown), Paratischeria guarani Diškus & Stonis, sp. nov. (feeding on Elephantopus mollis Kunth, Asteraceae), P. mesoamericana Diškus & Stonis, sp. nov. (feeding on Montanoa hibiscifolia Benth., Asteraceae), P. suprafasciata Diškus & Stonis, sp. nov. (feeding on Allophyllus edulis (A. St.-Hil., A. Juss. & Cambess.) Hieron. ex Niederl., Sapindaceae), and P. braziliensis Diškus & Stonis, sp. nov. (host plant unknown). Additionally, an updated distribution map of Paratischeria neotropicana (Diškus & Stonis, 2015), which currently has the broadest distribution range among the Neotropical Tischeriidae is provided along with new host-plant data, a list of all recorded host plants in the Neotropics, and a brief discussion on trophic relationships of Tischeriidae. It is hypothesized that host-plant distribution ranges can provide clues to potential distribution ranges of these specialized, monophagous or oligophagous, leaf miners. All new taxa are illustrated with photographs of the adults, their genitalia, and, if available, leaf mines.

We describe one new genus (Brachinepticula Stonis & Diškus, gen. nov.) with two new species (B. plurilobata Diškus & Stonis, sp. nov., B. elongata Remeikis & Stonis, sp. nov.), and one species with uncertain taxonomic position (Johanssoniella bina Remeikis & Stonis, sp. nov.). We also provide diagnostic characters and an updated annotated catalogue of the following related genera: newly restored Johanssoniella Koçak, Brachinepticula gen. nov., Enteucha Meyrick (s. str.) and Manoneura Davis. In the Annotated Catalogue, we provide five new combinations and new data on morphology, biology, and distribution of some species, including the first photographic documentation of Manoneura basidactyla Davis discovered in the Amazon rainforest, results of re-examination of the male genitalia of the European Johanssonia acetosae (Stt.), also the first documentation of the male genitalia, host plant and leaf mines of the little known Johanssoniella diplocosma (Meyrick) from the Himalayas. All new taxa treated in the paper are illustrated with drawings and (or) photographs of the adults and genitalia; photographs of the leaf mines of Brachinepticula plurilobata Diškus & Stonis, sp. nov. and Johanssoniella diplocosma (Meyrick) are also provided.

We describe seven new Neotropical species of Tischeriidae: Astrotischeria dondavisi Stonis & Diškus, sp. nov., A. bacchariphaga Diškus & Stonis, sp. nov., A. guatemalica Diškus & Stonis, sp. nov., A. sanjosei Stonis & Diškus, sp. nov., A. truncata Diškus & Stonis, sp. nov., Coptotriche parvisacculata Diškus & Stonis, sp. nov. and C. carmencita Stonis & Diškus, sp. nov. We report the discovery of Coptotriche Walsingham in South America and provide the following new host-plant records for the Neotropical Tischeriidae: Terminalia australis Cambess. (Combretaceae), Baccharis latifolia (Ruiz & Pav.) Pers., and B. emarginata (Ruiz & Pav.) Pers. (Asteraceae). We update the biology of Astrotischeria ochrimaculosa Diškus, Stonis & Vargas with the discovery that Wissadula (Malvaceae) is a new, verified host plant. The new species are illustrated with photographs of the adults, male and, if available, female genitalia, and the leaf mines. We expect broader distributions of tisheriid species in South America inferred from known host-plant distributions.

We report on fourteen species and four genera of Tischeriidae recorded from Las Cuevas, a single tropical forest locality in Belize, Central America. This is the highest number of species of Tischeriidae recorded from a single locality worldwide, exceeding the species and generic diversity of the entire Tischeriidae fauna of Europe and accounting for about 9% of the documented global fauna for this family. We describe and name six new species: Astrotischeria papilloma Diškus & Stonis sp. nov., mining on Lasianthaea fruticosa (L.) K.M.Becker (Asteraceae); A. scutifera Diškus & Stonis sp. nov., mining on Sida glabra Mill. (Malvaceae); A. basilobata Remeikis & Stonis sp. nov., mining on Lasianthaea fruticosa; Paratischeria robinsoni Diškus & Stonis sp. nov., mining on Otopappus verbesinoides Benth. (Asteraceae); P. tubifex Diškus & Stonis sp. nov., mining on Lasianthaea fruticosa; and P. belizensis Remeikis & Stonis sp. nov. (host plant unknown). Additionally, we review eight previously described species from the same period of collecting at Las Cuevas in 1997–1998: A. selvica Diškus, Carvalho-Filho & Stonis, 2018, mining on Sphagneticola trilobata (L.) Pruski and Synedrella nodiflora (L.) Gaertn. (Asteraceae); A. casila Diškus & Stonis, 2018, mining on Montanoa atriplicifolia (Pers.) Sch.Bip. (Asteraceae); A. furcata Diškus & Stonis, 2018 (host plant unknown); Paratischeria neotropicana (Diškus & Stonis, 2015), mining on Sida L. (Malvaceae), including S. rhombifolia L.; Dishkeya gouaniae (Stonis & Diškus, 2007), mining on Gouania polygama (Jacq.) Urb. (Rhamnaceae); Coptotriche pulverea (Walsingham, 1897), mining on Terminalia amazonia (J.F.Gmel.) Exell (Combretaceae); C. forsteroniae Stonis & Diškus, 2008, mining on Forsteronia myriantha Donn Sm. (Apocynaceae); and C. singularis Stonis & Diškus, 2008 (host plant unknown). All taxa, except for C. singularis, are illustrated with photographs of the adults and their genitalia. We also briefly discuss the discovery of some novel characters for Astrotischeria Puplesis & Diškus, 2003 and Paratischeria Diškus & Stonis, 2017, Tischeriidae, and provide the first photographic documentation of Coptotriche pulverea and C. forsteroniae.

We review forty-five species of Nepticulidae (Lepidoptera) based on an analysis of samples collected in the central Andean region of Peru and Bolivia. Thirteen of these species are new to science, and are named and described here: Stigmella paracosma Remeikis & Stonis, sp. nov., S. expressa Remeikis & Stonis, sp. nov., S. acalyphae Diškus & Stonis, sp. nov., S. lepida Diškus & Stonis, sp. nov., S. misera Diškus & Stonis, sp. nov., S. inca Diškus & Stonis, sp. nov., S. eiffeli Diškus & Stonis, sp. nov., S. arequipica Remeikis & Stonis, sp. nov., S. coronaria Diškus & Stonis, sp. nov., S. azulella Diškus & Stonis, sp. nov., S. sparsella Diškus & Stonis, sp. nov., Manoneura forcipis Diškus & Stonis, sp. nov., and Acalyptris murex Diškus & Stonis, sp. nov. Some of the central Andean species are recorded here as leaf-miners on Euphorbiaceae (Acalypha), Fabaceae (Collaea), Rosaceae (Polylepis), Malvaceae (Sida), Calceolariaceae (Calceolaria), Lamiaceae (Clinopodium), and Asteraceae (Ageratina and Trixis). We create eleven new species groups based on morphological characters designated in Stigmella and one in Acalyptris. A pictorial key to the species groups and distribution maps are provided. All new species are illustrated with 150 photographs and drawings of the adults and genitalia, and, where known and/or available, photographs of host-plants and leaf-mines.

We record the first Nepticulidae species found to feed on Baccharis L. (Asteraceae). Despite the high species richness of Baccharis in the Western Hemisphere, no nepticulid has ever been recorded feeding on Baccharis. In this paper we describe six new Stigmella Schrank species feeding on Baccharis: S. emarginatae Diškus& Stonis, sp. nov., S. bipartita Diškus & Stonis, sp. nov., S. tripartita Diškus & Stonis, sp. nov., S. latifoliae Remeikis, Diškus & Stonis, sp. nov., S. baccharicola Diškus & Stonis, sp. nov., and S. confertae Diškus & Stonis, sp. nov. The remaining two taxa are left unnamed. All taxa are illustrated with photographs of adults, their genitalia, and their leaf-mines. Additionally, leaf-mines on Baccharis salicifolia are documented.

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