Riodinidae

Distinguished from the closely related Lycaenidae by several morphological features: male forelegs with coxae that extend beyond the joint with the trochanter (versus flush meeting in Lycaenidae); presence of a humeral vein in the hindwing and thickened costa (absent in most Lycaenidae); and a wider head with antennal bases more distant from the eyes. The reduced male forelegs are shared with Lycaenidae but differ in detail: Riodinidae forelegs are markedly shorter and have differently constructed coxal projections. Female Riodinidae possess sensory hairs on the foreleg tarsi arranged in paired groups, a feature shared with other Papilionoidea but with distinct arrangement. The absence of posterior apophyses in female genitalia is problematic as this occurs in some Poritiinae (Lycaenidae) as well. Chromosome numbers are exceptionally variable (9–110), unlike the relatively stable numbers in related families.

Primarily tropical rainforest habitats, with greatest diversity in the Neotropics. Many species occupy restricted geographic ranges. Some lineages extend into temperate zones including sagebrush habitats in western North America. Specific habitat associations vary: some species linked to particular host plant communities, others to ant-tended environments. The family shows a unique distribution focus in South American tropical rainforests, with species of genus Charis used to reconstruct historical Amazon forest fragmentation patterns.

Predominantly Neotropical, with the highest diversity in Central and South America. Also represented in the Nearctic (including western North America), Palearctic, Australasian (genus Dicallaneura), Afrotropic (genera Afriodinia, Saribia), and Indomalayan realms. Distribution records from GBIF include Denmark and Sweden, indicating limited Palearctic presence.

Larvae feed on plants from more than 40 families, with records including Araceae, Asteraceae, Bromeliaceae, Bombacaceae, Cecropiaceae, Clusiaceae, Dilleniaceae, Euphorbiaceae, Fabaceae, Lecythidaceae, Loranthaceae, Malpighiaceae, Marantaceae, Melastomataceae, Myrtaceae, Orchidaceae, Rubiaceae, Sapindaceae, and Zingiberaceae, as well as bryophytes and lichens. Feeding typically targets young leaves or flowers; rarely on fallen dead leaves or lichen. Larvae of Setabis lagus are predatory, feeding on treehopper larvae (Membracidae) and scale insects (Coccidae). Adult feeding records from Ecuador indicate rotting fish and carrion as the most frequently used food source for males, with flowers and damp sand also visited.

• Plants from >40 families - larval hostPrimary feeding on young leaves and flowers
• Membracidae (treehoppers) - preyPredatory larval feeding in Setabis lagus
• Coccidae (scale insects) - preyPredatory larval feeding in Setabis lagus and Alesa amesis
• Ants (~280 species) - mutualismMyrmecophily with larvae tended and protected by ants; tentacle nectary organs secrete fluids consumed by ants

Eggs are round and flattened, dome-shaped, or turban-shaped, similar to Lycaenidae eggs. Caterpillars are typically hairy and plump, usually longer than Lycaenidae caterpillars except in myrmecophilous species. The caterpillar is the common overwintering stage. Pupae are hairy and attached with silk to host plants or ground debris; no cocoon is formed. Developmental timing from a laboratory study of Hyphilaria thasus: third instar to pupation in 3 days, adult emergence 16 days after pupation. Gregarious caterpillars occur in Euselasiinae (Euselasia), Riodinini (Melanis), and Emesini (Emesis), with some species showing processionary behavior.

Extensive myrmecophily: larvae of many species possess tentacle nectary organs on the eighth abdominal segment that secrete fluids consumed by attending ants, and tentacle organs on the third thoracic segment that emit allomones influencing ant behavior. Caterpillar acoustic signals appear to enhance ant symbioses. Batesian mimicry is exceptionally common, with many species mimicking toxic moths or nymphalid butterflies; this has caused closely related species to evolve divergent wing patterns. Adult males frequently visit rotting fish and carrion. Some larvae are gregarious with processionary behavior.

Herbivores in diverse plant communities, with some species acting as predators on other insects. Myrmecophilous species engage in mutualisms with ants, contributing to complex food web interactions. Mimicry complexes influence community structure and predator learning. Some species serve as hosts for parasitoids including tachinid flies (Lespesia archippivora recorded from Hyphilaria thasus). A few species are minor agricultural pests on cultivated bromeliads, orchids, or Myrtaceae.

Generally of low economic importance. Some Euselasiinae species feed on economically important Myrtaceae such as guava. A few Riodininae are reported as pests of cultivated Bromeliaceae or Orchidaceae. Primarily of scientific interest for studies on mimicry, myrmecophily, and biogeography. Some species used as indicators for historical habitat reconstruction (e.g., Charis species for Amazon forest history).

• LycaenidaeSister family with shared reduced male forelegs and myrmecophily; distinguished by male foreleg coxal structure, hindwing venation, head proportions, and antennal length
• SatyrinaeSome Riodinidae species resemble satyrs in wing shape and coloration; distinguished by metallic spotting (when present) and morphological features of legs and wing venation
• ColiadinaeSome bright yellow Riodinidae species reminiscent of sulphurs; distinguished by structural coloration and leg morphology
• PapilionidaeTailed species in genera Barbicornis, Rhetus arcius, Helicopis, and Chorinea resemble swallowtails; distinguished by smaller size, metallic markings, and leg structure

• butterflies
• metalmarks
• myrmecophily
• mimicry
• Neotropical
• Lepidoptera

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• La Reserva Ecologica Costanera Sur | Beetles In The Bush
• Ant bodyguards here and there: Odorous house ants, Tapinoma sessile, and carpenter ants, Camponotus — Bug of the Week
• A rare opportunity to do fall insect collecting in western North America | Beetles In The Bush
• First record of Aricoris campestris (Bates, 1868) Lepidoptera: Riodinidae in pitaya in northeastern Brazil
• Descriptions of four new Mexican riodinids (Lepidoptera: Riodinidae)
• Observaciones biológicas de Hyphilaria thasus (Stoll) (Lepidoptera, Riodinidae) y su parasitoide en Panamá
• A new Mexican Mesene (Lepidoptera, Riodinidae)
• A new species of Pheles Herrich–Schaeffer from Northeast Brazil (Lepidoptera, Riodinidae)
• Four new symmachiine taxa from the eastern Andes of Peru and Ecuador  (Lepidoptera: Riodinidae)