A common classification of theLepidoptera involves their differentiation intobutterflies andmoths. Butterflies are a naturalmonophyletic group, historically treated as the suborderRhopalocera, which includesPapilionoidea (true butterflies),Hesperiidae (skippers), andHedylidae (butterfly moths). In this taxonomic scheme, moths formed the suborderHeterocera. Other taxonomic schemes have been proposed, the most common putting the butterflies into the suborderDitrysia and then the "superfamily"Papilionoidea and ignoring a classification for moths.
While the butterflies form amonophyletic group, the moths, which comprise the rest of the Lepidoptera, do not. Many attempts have been made to group the superfamilies of the Lepidoptera into natural groups, most of which fail because one of the two groups is not monophyletic: Microlepidoptera and Macrolepidoptera, Heterocera and Rhopalocera, Jugatae and Frenatae, Monotrysia and Ditrysia.[1]
Although the rules for distinguishing these groups are not absolute, one very good guiding principle is that butterflies have thin antennae and (with one exception) have small balls or clubs at the end of their antennae. Moth antennae can be quite varied in appearance, but in particular lack the club end. The divisions are named by this principle: "club-antennae" (Rhopalocera) or "varied-antennae" (Heterocera).
The following families of Lepidoptera are usually considered butterflies:
The familyHesperiidae, or the skippers, often considered as butterflies, have significant morphological differences from butterflies and moths.
The other families of the Lepidoptera are considered moths.
The most obvious difference is in the feelers, orantennae. Most butterflies have thin slender filamentous antennae which are club shaped at the end. Moths, on the other hand, often have comb-like or feathery antennae, or filamentous and unclubbed.[2][3] This distinction is the basis for the earliest taxonomic divisions in the Lepidoptera: theRhopalocera ("clubbed horn", the butterflies) and theHeterocera ("varied horn", the moths).
There are, however, exceptions to this rule and a few moths (the familiesCastniidae,Uraniidae,Apoprogonidae,Sematuridae,[4] and some members ofSphingidae) have clubbed antennae. Some butterflies, likePseudopontia paradoxa from the forests of centralAfrica, lack the club ends. Thehesperiids often have an angle to the tip of the antenna, with the clubs hooked backwards like acrochet hook.
Many moths have afrenulum which is a filament arising from the hindwing and coupling (matching up) with barbs on the forewing. The frenulum can be observed only when a specimen is in hand. There is only one known species of butterfly with a frenulum, which is the male regent skipperEuschemon rafflesia.[5] Some moths have a lobe on the forewing called a jugum that helps in coupling with the hindwing. Butterflies lack these structures.
Most mothcaterpillars spin acocoon made of silk within which theymetamorphose into thepupal stage. Most butterfly caterpillars, on the other hand, form an exposed pupa made from a hardened protein, also termed achrysalis.
There are many exceptions to this rule, however. For example, thehawk moths form an exposed pupa which is underground.Spongy moths sometimes form butterfly-style pupae, hanging on twigs or tree bark, although usually they create flimsy cocoons out of silk webbing and leaf bits, leaving the pupa exposed. The plume winged moths of the familyPterophoridae also pupates without a cocoon and the pupa resembles the chrysalis of thepierid butterfly. A few skipper butterfly larvae also make crude cocoons in which they pupate, exposing the pupa a bit. TheParnassius butterfly larvae make a flimsy cocoon for pupation and they pupate near the ground surface between debris.
Most butterflies have bright colours on their wings. Nocturnal moths on the other hand are usually plain brown, grey, white or black and often with obscuring patterns of zigzags or swirls which helpcamouflage them from predators as they rest during the day. However, many day-flying moths are brightly coloured, particularly if they aretoxic. Thesediurnal species evolved to locate their mates visually and not primarily bypheromone as their drab nocturnal cousins.[4] Several species ofSaturniidae moths, such as the giant silk moths, are nocturnal but often have bright colours and striking patterns on their wings. A few butterflies are also plain-coloured, like thecabbage white butterfly or thebaron butterfly.
Moths tend to have stout and hairy or furry-looking bodies, while butterflies have slender and smoother abdomens. Moths have larger scales on their wings which makes them look more dense and fluffy. Butterflies on the other hand possess fine scales. This difference is possibly due to the need for moths to conserve heat during the cooler nights, or to confoundecholocation by bats, whereas butterflies are able to absorbsunlight.
Despite appearances, butterflies and moths have different types ofcompound eyes. Though not universal, moths very commonly havesuperposition eyes, while butterflies equally commonly favourapposition eyes. This is due to the superposition eye's adaptations for low light environments suiting the nocturnal moths, and the apposition eye's superior resolution and potential for colour vision benefiting the more diurnal butterflies.[6]
There are several exceptions to this rule, such as with the diurnalZygaenidae and Sytomidae families of moths, both of which have apposition eyes, or theHedyloidea family of butterflies, which are nocturnal and feature superposition eyes.[7] In most cases where one species is found to be using the opposite type of eye than expected, it is because they are active during the opposite time of day than is normal for other butterflies or moths.
Most moths arenocturnal orcrepuscular while most butterflies arediurnal. There are however exceptions, including the spectacularUraniidae or sunset moths. A few species, such as the male European/North Americanspongy moth, fly during both day and night in search of the females, which are flightless.
Moths usually rest with their wings spread out to their sides. Butterflies frequently fold their wings above their backs when they are perched although they will occasionally "bask" with their wings spread for short periods (several types ofSwallowtail butterflies tend to frequently rest with their wings spread when in sunlight). However, some butterflies, like theskippers, may hold their wings either flat, or folded, or even in-between (the so-called "jet plane" position) when perched.
Most moths also occasionally fold their wings above their backs when there is no room to fully spread their wings.
A sometimes confusing family can be theGeometridae (such as thewinter moth) because the adults often rest with their wings folded vertically. These moths have thin bodies and large wings like many butterflies but may be distinguished easily by structural differences in their antennae (e.g.bipectinate).
