The study of the material collected along the Pacific Coast of Mexico in 2008 has resulted in the discovery of six new species of Nepticulidae. Three species are described and named Stigmella racemifera Šimkevičiūtė & Stonis, sp. n., Acalyptris paradividua Šimkevičiūtė & Stonis, sp. n. and A. terrificus Šimkevičiūtė & Stonis, sp. n., and the other three species belonging to Stigmella and Acalyptris are documented, but not named pending the availability of additional material. The taxonomic checklist of the Mexican fauna of Nepticulidae is provided for the first time. Illustrations of adults and male genitalia of all species reported in the checklist are given together with a distribution map.

The world’s smallest moths in Lepidoptera (Insecta) and the complexity in making such a determination are examined and discussed. The forewing length and wingspan of 650 species were measured and the same data were retrieved from published papers to determine which species and family have the smallest moths in the world. The minimal recorded forewing length was found to be around 1.2–1.3 mm and the wingspan around 2.6–2.8 mm in two families, the Gracillariidae and Nepticulidae. Among Lepidoptera, the following species have the smallest moths globally: the European Johanssoniella acetosae (Stainton), the Peruvian Simplimorpha kailai Stonis & Diškus, the Mexican Stigmella maya Remeikis & Stonis, the Mediterranean S. diniensis (Klimesh), the Mediterranean Parafomoria liguricella (Klimesh) (Nepticulidae), the South East Asian Porphyrosela alternata Kumata, and the Central African P. desmodivora De Prins (Gracillariidae). Additionally, in the Nepticulidae, we provide a measurement update for Stigmella maya Remeikis & Stonis, one of the tiniest species with a forewing length of 1.3 mm and wingspan of 2.8 mm, and describe a new species, Stigmella incaica Diškus & Stonis, sp. nov., with a forewing length of 1.75 to 1.95 mm and a wingspan of 3.8 to 4.3 mm.

For the first time, genera of leaf mining Tischeriidae of the global fauna are reviewed and four new genera are described: Coptotrichoides Diškus & Stonis, gen. nov., trophically associated with Sapindaceae from Central and South America; Rytietia Diškus, Xu & Dai, gen. nov., trophically associated with Annonaceae from East and South East Asia; Pafazaria Diškus & Stonis, gen. nov., trophically associated with Fabaceae and Malvaceae from East and South East Asia; and Gnathitischeria Diškus, gen. nov., trophically associated with Malvaceae and Asteraceae from Central America. In addition to the descriptions of new genera, all previously described genera (Coptotriche Walsingham, 1890; Dishkeya Stonis, 2020; Tischeria Zeller, 1839; Manitischeria Diškus & Stonis, 2021; Neotischeria Diškus & Stonis, 2021; Paratischeria Diškus & Stonis, 2017; and Astrotischeria Puplesis & Diškus, 2003) are characterized and a pictorial identification key for all 11 genera is provided. Morphological and biological characteristics of all genera are supplemented with some molecular data. We described 12 new species: South East Asian Coptotriche sapaensis Diškus & Stonis, sp. nov.; Central American Coptotrichoides sapindoidum Diškus & Stonis, sp. nov. and Tischeria neokristenseni Diškus & Stonis, sp. nov.; South East Asian Rytietia uncinata Diškus, Xu & Dai, sp. nov., East Asian R. chongyiensis Xu & Dai, sp. nov.; South East Asian Pafazaria capitata Diškus & Stonis, sp. nov. and P. faboidica Diškus & Stonis, sp. nov.; Central American Neotischeria antigua Diškus & Remeikis, sp. nov. and N. subantigua Diškus & Remeikis, sp. nov.; South American Astrotischeria incae Diškus & Stonis, sp. nov.; and Central American Gnathitischeria atitlani Diškus & Stonis, sp. nov. and G. arcana Diškus & Stonis, sp. nov. The taxonomic rank of the East Asian subspecies Tischeria decidua siorkionla Kozlov, 1986 is elevated to species rank: T. siorkionla Kozlov (stat. nov.). The male genitalia of holotypes, paratypes, lectotypes or paralectotypes, or non-type specimens of some little-known species are examined for the first time. We provide the first morphological documentation for the following: Tischeria ceanothi lectotype and paralectotype; T. immaculata (stat. restored) paratype; Coptotrichoides deliquescens (Meyrick) lectotype and paralectotype; lectotypes of Coptotriche aenea (Frey & Boll), Astrotischeria plagifera (Meyrick), A. helianthi (Frey & Boll), and A. ephaptis (Meyrick); Coptotriche berberella (De Prins) paratype; and the first photographic documentation of Tischeria lvoskyi Kozlov holotype. Some non-type specimens deposited at NHMUK, including a few previously neglected species, are also examined and documented, including the American Astrotischeria solidagonifoliella (Clemens) and A. omissa (Braun). Nine new combinations are provided: Coptotrichoides deliquescens (Meyrick, 1915), comb. nov.; C. singularis (Stonis & Diškus) comb. nov.; C. suprafasciata (Diškus & Stonis) comb. nov., C. serjaniphaga (Remeikis & Stonis) comb. nov.; C. braziliensis (Diškus & Stonis) comb. nov.; Pafazaria jingdongensis (Xu & Dai), comb. nov.; Neotischeria explosa (Braun) comb. nov.; N. pallidipennella (Braun) comb. nov.; and Astrotischeria heteroterae (Frey & Boll) comb. nov. The synonymization of Tischeria longeciliata Frey & Boll, 1878 with Astrotischeria helianthi (Frey & Boll, 1878) is confirmed. One new species group, the Tischeria ceanothi group, is established. We also report a new distribution record of T. dodonaea Stainton from the Caucasus, Armenia. Three tables and 569 figures of adult external morphology, male and female genitalia, leaf mines, and cladograms based on molecular characters are provided.

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.

The article describes three new species of Coptotriche Walsingham, 1890 from China and adjacent northern Vietnam: C. camptotheca Xu & Dai, sp. nov. feeding on Camptotheca acuminata Decne. (Nyssaceae); C. turpinia Xu & Dai, sp. nov. feeding on Turpinia arguta (Lindl.) Seem. (Staphyleaceae); and C. asiana Diškus & Stonis, sp. nov. The latter appeared to be a narrow oligophagous species feeding on various Symplocos Jacq.: S. sumuntia Buch.-Ham. ex D. Don, S. poilanei Guill., and Symplocos glauca (Thunb.) Koidz. (Symplocaceae). Nyssaceae and Staphyleaceae are novel host-plant families of Tischeriidae. The new species are illustrated with photographs of adults, male and female genitalia, and leaf mines. The article also briefly discusses about the proportion of monophagous and oligophagous species of Tischeriidae.

This study identifies the number of named and described species of three monotrysian, plant-mining lepidopteran families worldwide: Nepticulidae and Opostegidae (Nepticuloidea), and Tischeriidae (Tischerioidea). At the end of 2021, we estimated that a total of 1000 Nepticulidae species, 197 Opostegidae species, and 170 Tischeriidae species have been described since the taxonomic practice of describing species began in the 18th century. We examine and discuss the history of descriptions and authorship of species worldwide for each of the three families. We found that the total (accumulative) number of species described increased with each time period delineated. About five new species were described per year on average, or about 22 new species were described per year in the 21st century. We recognize researchers with the most number of described species in these three taxa.