Glossary of Butterfly Terms

This page contains a list of butterfly related terms and their definitions.


The breeding, final, and most conspicuous stage of the Lepidoptera multistage life cycle. Sometimes called the “imago”. The lifespan of adult butterflies ranges from a few weeks to several months, depending on species and environment.


Any one of a number of alternative forms of a gene. For examples, in Colias sulphur butterflies, a certain gene codes for the wing color, and most of the alleles in population for that trait code for orange or yellow wings. However, another allele of that gene codes for white wings instead, although it is exclusively expressed in females. In humans, blood types (A, B, AB, O, etc) are determined by different alleles of the same gene.


The separation of populations or taxa by geographic distance.  Allopatry is suggested to be the primary means of evolutionary radiation through adaptations to differing conditions or habitats in different areas.  Compare to “Sympatric” below.


The second stage of Lepidoptera metamorphosis.  The primary activity in this stage is eating, eating, and eating.  In fact, it is only the larval stage of a butterfly or moth that grows and “runt” adults can result from a poor diet as a caterpillar.


A vegetation type characterized by dense, generally evergreen shrubs that usually experience hot dry summers and cool, wet winters.  The lower elevations of many California mountain ranges are covered in chaparral, especially on more exposed, south-facing slopes.


The third stage in Lepidoptera metamorphosis (also called the pupa).  The body tissues and organs of the caterpillar are broken down and re-arranged to develop the adult.  The chrysalis is the most vulnerable stage because the individual does not have any ability to move if threatened by enemies or adverse environmental conditions.


A taxon that periodically establishes breeding populations in a region but are not usually permanent breeding residents (although they have the potential to if conditions are suitable).

Convergent evolution

When two or more unrelated taxa independently develop similar morphologies or other traits, usually through similar selection pressures. Traits that develop in this manner are called “homoplasies”. An example is the independent development of wings in insects, birds, pterosaurs (flying dinosaurs), and bats.


Primarily active in twilight hours, either in the early morning or early evening.


Markings on the body of an animal that allow it blend in with aspects of their environment and make it difficult to observe. Also commonly known as camouflage.

Cryptic species

Taxa that upon initial observation are not obviously different from each other and only are found to have important differences in morphology, genotype, or life history after detailed inspection.


An extended resting period, or torpor, where an organism remains relatively inactive and metabolic activities are largely reduced to survive periods when conditions are too harsh to survive normally.


A trait that displays two distinct forms.


A roughly circular region on Lepidoptera wings located near a patch completely enclosed by certain wing veins.  The discal area is located on the front edge of the center of forewings, and near the body in the center of the hindwing.


The “upperside” of an insect’s body. In butterflies, the dorsal surface is visible when the wings are held open. In humans, this is equivalent to the “back” side of our bodies.


The field of biology that studies the interactions between organisms and aspects of their environment.


An “ecological race” of an organism that is distinct from other related taxa because of different ecological or environmental associations, though it may not be taxonomically named (i.e. named). An example from this research is the Anise Swallowtail.


The first stage in the metamorphosis of insects. Eggs are normally placed by female Lepidoptera on suitable plants that can provide nutrition for the developing larvae to eat, although chemical cues can be misinterpreted and eggs are sometimes placed on inappropriate substrates.


Inactivity by an organism during the warm summer months.

Evolutionary Radiation

The divergence through time of morphological, genetic, or ecological characters; often leading to speciation.


When an organism that had been formerly been present at a site is presumed to be completely absent. If the organism is no longer found anywhere, it is “globally extinct”.


A ringed pattern present on the wings or bodies of some animals, such as the Buckeye butterfly and most satyr butterflies.


Optional (e.g. diapause in multi-brooded species); usually cued by environmental conditions.


The nested rank between order and genus in the Linnaean system.  Six butterfly families are present in western North America: Hesperiidae (skippers), Papilionidae (swallowtails and parnassians), Pieridae (whites and sulfurs), Lycaenidae (coppers, hairstreaks, and blues; a.k.a. the gossamer-wings), Riodinidae (metalmarks; placed within Lycaenidae by some authors), and Nymphalidae (brushfoots, including fritillaries, checkerspots, crescents, admirals, satyrs, and monarchs).


The front pair of wings on an insect (closer to the head). The forewings provide structural support and are the primary mechanisms of lift for flight. Species with pointier forewings are generally faster, more direct fliers, while those with rounded forewings are usually slower and more maneuverable.


The collection of all genes and non-coding DNA in an organism.


The unique composition of an individual’s genetic makeup, especially relating to its different alleles, either within genes or across genes.


The nested rank between family and species in the Linnaean system.


A rock roughly equivalent to granite, which is formed deep within the earth at high temperatures and pressures. It is a common rock type in the higher elevations of the Sierra Nevada and becomes crumbly as it erodes.


Inactivity by an organism during the cold winter months.


The behavior of some insect species to concentrate on or patrol around the summits of mountains or ridges.  Males are more likely than females to engage in this “King of the Mountain” behavior, but females do seek out these high points in order to mate.  In our fauna, classic hilltoppers include the Western White and Anise Swallowtail.  Hilltopping is one of several “epigamic” behaviors: behaviors that serve to bring the sexes together.


The rear pair of wings on an insect. The hindwings primarily are used for stability and increased surface area in flight. When butterflies land with their wings closed (and most do), the ventral hindwings is the primary wing surface observed. Some species have complex color patterns and designs on this wing surface, including eyespots and tails that may draw the attention of predators away from more “critical” areas of the body like the head and forewings. These patterns also can serve as important means of species recognition in courtship (demonstrably so in the Lycaeides blues). In others, like Ceryconis wood nymphs, ventral hindwings are cryptic and serve as camouflage.


Organisms whose geographic ranges span both North America and Eurasia.

Host plant

The species or set of species of plants that caterpillars must eat to develop properly. Host plant specificity can vary greatly across butterfly species, ranging from only 1 plant species to dozens of suitable plant species. Host plant specificity can promote speciation between two or more groups of closely related through reproductive isolation. Prime examples of this are Euphilotes blue butterflies and some Apodemia metalmarks that almost exclusively use different species or varieties buckwheats (Eriogonum) as larval hosts. A similar situation has been demonstrated in Mitoura hairstreaks that feed on trees in the family Cupressaceae (junipers, incense-cedar, cypresses).


When two taxa are able to interbreed to produce viable offspring (although the offspring are not necessarily fertile themselves, as in a mule).


The stage between molts in the life of larvae. Butterflies belong to the Phylum Arthropoda (which includes other animals like crustaceans, spiders, millipedes, as well as all other insects), and all Arthropods must molt their external skeleton (a.k.a. exoskeleton) because it does not grow continuously like the internal skeleton (a.k.a. endoskeleton) of vertebrates. Most butterfly larvae molt their exoskeleton about 5 times and therefore have 6 instars, but environmental conditions can alter the number.

International Code of Zoological Nomenclature

The set of formalized rules for describing species and other taxa; the judicial body that makes decisions on taxonomic conflicts based on the Code and is called the International Commission on Zoological Nomenclature.


A species or other taxon that is transported or disperses, accidentally or intentionally, to a new locality, where it may be come naturalized or weedy. For instance, most of the dominant plants in the Central Valley of California are actually endemic to the Mediterranean region of southern Europe and north Africa where seasonal patterns of dry and wet, hot and cold, conditions are extremely similar. Many of these species arrived in California in the late 19th and early 20th centuries through human related activities. Interestingly, many butterflies in lowland California are now dependent to some degree on these introduced plants.


The concentration of males into a small area for the purposes of collectively displaying to females as potential mates. Females are allowed to “choose” the strongest, flashiest, sexiest, etc., male in the group, and as a result, only a handful of males usually mate. Hilltops are one place where such behavior occurs.


The order of insects containing all butterflies and moths under the Linnaean system. It is the second largest order of animals on earth with about 180,000 described species worldwide, although only 10-15% of the Lepidoptera are butterflies. Only the beetles (order Coleoptera) are more speciose with at least 350,000 species (and perhaps 1,000,000!). Lepidoptera translates from ancient Greek as “scaly-wing" (lepido-pteron), referring to the small scales that cover their wings and bodies. Almost all Lepidoptera feed on plants (with varying degrees of specificity) in the larval stage, but a few have become specialist predators on aphids and ant larvae.

Life History

The who, what, when, where, and how of an organism. Life history information relies on detailed observations of the activities and happenings of organisms under “natural” conditions and can be extremely laborious to gather, but is absolutely essential in environmental studies and especially conservation biology.

Linnaean system

The generally accepted, rank-based, system of classifying organisms and giving them scientific names, formalized by the Swedish biologist Carolus Linnaeus in the 18th Century.


When populations of an organism are found only in small patches, even though those populations may be very abundant or the overall geographic range of the organism is vast. For example, populations of the Arctic Skipper are found in very small areas but the species has a circumboreal distribution.


The physical location of a particular genetic sequence (a gene or a non-coding section of DNA) in the genome, especially on the chromosomes. Often used loosely as a synonym of “gene”.


The transformation of an organism into different looking forms as it develops. Insects like butterflies and moths, and bees, wasps and ants (order Hymenoptera), beetles (order Coleoptera), and flies (order Diptera) undergo “complete” metamorphosis (a.k.a. holometabolism). In this 4-stage process, adults lay eggs, from which larvae hatch, develop into the chrysalis in the pupal stage, and then transform into and emerge as the adult. Other insect orders, including dragonflies and damselflies (order Odonata) and the true bugs (order Hemiptera) develop through “incomplete” metamorphosis (a.k.a. hemimetabolism) in which eggs hatch into nymphs which gradually transform into adults in successive instars.


A rock type that is composed of formerly small-sized particles (“sedimentary”, like the grains of sands on lakeshores) that are then exposed to high pressures and temperatures and become compacted into solid stone and are altered chemically.


The long-distance dispersal of individual organisms from one locality to another, usually to optimize reproductive and feeding success. In true migration (like in many birds), the same individual will make a roundtrip. For most butterflies, “migration” is one-way only. In our fauna, the most famous migratory species are the Monarch, Painted Lady, and California Tortoiseshell.


The resemblance of two or more unrelated organisms to each other, usually because at least one is toxic, distasteful, or dangerous and the “mimics” are able to gain protection from enemies by resembling them. In “Batesian mimicry”, there is one nasty model and at least one benign mimic, while in “Müllerian mimicry”, there are multiple nasty models that all look alike. In our butterfly fauna, the Pipevine Swallowtail acquires dangerous chemicals from its hostplant and is unpalatable and has no mimics in California, but near the center of its historic range around the southeastern U.S. (as inferred from genetic studies), it is mimicked by several unrelated butterfly species. Also see “Crypsis” above.


Pertaining to the mountains, especially in between about 3000’ and 7000’ in the Sierra Nevada where conifer forests dominate.


The study of the physical structures of living organisms and the organization of those structures.


A taxon whose description is based solely on morphological data, without the support of genetic or ecological information.


The process of establishment of non-native species into a region as permanent, wild, and naturally regenerating. These species may become invasive exotics that can alter ecosystem dynamics if they out-compete or displace native species.


A very young individual that is particularly vulnerable to environmental dangers.


A term used to denote that the scientific name of the taxon being discussed is the same at the species and subspecies level.


The rank nested between class and family in the Linnaean system. All butterflies and moths are in the order Lepidoptera.

Overwintering stage

The stage (egg, larva, pupa, or adult) in which butterflies hibernate through the winter months. Different species hibernate in different stages, and this affects the timing of activity by adults during the warmer months.


The placement of an egg on a substrate by a female.


An organism that persists in the same place for more than one year (at least), especially pertaining to plants that do not sprout, grow, mature, reproduce, and die within one year.


The study of patterns of biological activity through seasons. From a butterfly perspective, this often entails the timing of development through metamorphosis and adult flight periods and breeding through the year. The phenology of a species is heavily affected by host plant development and weather conditions.


What a particular trait looks like or how it is expressed physically through the interactions between genes and environmental effects. Examples are height and eye color in humans, or the patterns of differently colored scales on the wings of butterflies.


A branching, tree-like description of the evolutionary relationships between several taxa based on shared, derived characteristics. It is hoped that this explanation accurately depicts the pattern of evolutionary divergence between taxa. However, information is always at least somewhat incomplete, and resolving the “best” phylogeny employs several complex fields of probability theory and must be viewed as “educated guesses”.


The period of time (“epoch”) between about 1.8 million and 11,500 years ago, during which the last major Ice Age occurred. The distribution of many North American butterflies (indeed, many butterflies globally) appears to have been dramatically affected by the massive glaciers that covered the higher latitudes of the Northern hemisphere (and parts of the Southern hemisphere as well). Many plants and animals have relictual distributions as a result, with hundreds or even thousands of miles between populations.


A trait that displays two or more distinct forms.


The tube-like organ on the head of butterflies and moths that they use to drink fluids, like flower nectar. Lepidoptera do not have chewing mouthparts as adults and consequently do not consume solid food or grow as adults, but they definitely do as larvae!


The attraction, and usually concentration, of individual butterflies at wet, muddy spots to drink water and salts. For the most part, only males mudpuddle because they need salts to facilitate sperm production.


The period of time between about 1.8 million years ago (the beginning of the Pleistocene epoch) and the present, merging the Pleistocene and the Holocene or “Recent”.


An organism or population that is geographically isolated from other conspecifics or closely related taxa, often by a very long distance and the result of isolation by changes in climate.


The maintenance of year-round, breeding populations by a species at any given locality.


Occurring along creeks, rivers, or other bodies of fresh water. These wetter habitats are usually characterized by different flora and fauna than their adjacent upland habitats. The Pipevine Swallowtail and Lorquin’s Admiral are characteristic riparian butterflies.


Very small, flattened modified hairs that cover the wings and bodies of butterflies and moths. In butterflies, scales are usually arranged like overlapping shingles on a roof. The different colors and arrangements of these scales are what give butterfly and moth wings their different patterns. Colors are produced through chemical pigments, iridescence, or both.

Secondary compounds

Unique chemicals produced by plants that are frequently used as defenses against herbivores and other enemies. These may be poisonous and/or unpalatable. For example, the California pipevine (Aristolochia californica) produce unique chemicals called aristolochic acids that do severe damage to DNA and are extremely distasteful. However, their sole herbivore in California, the Pipevine Swallowtail, stores those acids in its body and uses them for its own defense. Most butterflies select host plants based on secondary chemistry.


A rock type derived from subducted ocean floor material that are characterized by unusually high concentrations of magnesium, chromium, manganese, cobalt, and nickel. Sodium and calcium are in unusually low concentrations. As a result, few plants are able to grow on these soils, and those that can are usually “edaphic endemics” (see above) and exhibit stunted growth patterns. Serpentine habitats also frequently are home to unique animals (for example see the Sleepy Dusky-wing or Muir’s Hairstreak). In this study, large portions of the “Washington” sampling site are serpentine.


The processes through which different populations or groups of organisms become reproductively isolated from each other to form different species. These can arise from genetic changes, ecological or environmental differences, or physical or behavioral isolation, or any combination thereof.


The primary unit of classification below genus under the Linnaean system. For our purposes, groups of interbreeding or potentially interbreeding populations of individuals that share an evolutionary history and ancestry. However, there is significant debate on what exactly constitutes a species and many definitions and concepts have been proposed. The most common of these is the biological species concept, which requires that sets of populations must be able to successfully and regularly interbreed and produce viable, fertile offspring.


Habitats that are characterized by grasses and low shrubs and are dry for most of the year. The Great Basin (between the Sierra Nevada and Rocky Mountains) is largely steppe dominated by sagebrush (Artemisia).


A patch of modified scales (“androconia”) on the wings of males of some butterfly species that release pheromones during courtship with females. The stigma is usually located on the dorsal forewing of many hairstreaks (Family Lycaenidae) and skippers (Family Hesperiidae), but may be located on the hindwings or near the body in other butterfly families.


An organism that is unexpectedly recorded outside of its normal geographic range. In most cases, strays are unable to breed in these new locations because of a lack of suitable food and shelter.


Taxa below species level that are perceived to have at least some degree of consistent differences in morphology, genotype, and/or life history, and are usually geographically or seasonally differentiated (although they often “blend” together in areas of sympatry). There are no formal rules or even general guidelines regarding the use and designation of subspecies names, and consequently subspecies names are often controversial and inconsistent.


When two taxa co-occur in the same place. Compare to “Allopatric” above.


A named grouping of organisms based on some degree of similarity or relationship. Can be applied to any level of taxonomic organization.

Taxon Range

The total area where a taxon maintains resident populations.


The classification of organisms into taxa.


The “defense” or regular patrolling behavior of some organisms (including apparently some butterfly species) of certain location. Territoriality in butterflies appears to be “epigamic” in function; females come to the sites where males are. It often occurs only at specific kinds of sites and times of the day, especially in the late afternoon and near dusk. These can range from the size of a small bush in the sunlight in an otherwise dark forest, or an entire stream system. Most territorial behavior in butterflies is done by males, who will chase at almost anything that flies by (including potential enemies like birds and butterfly scientists!).


A line along which environmental data is collected. In this study, the 10 locations that have been regularly sampled for butterfly diversity is roughly along a transect line paralleling U.S. Interstate 80 from the eastern San Francisco delta through the Sacramento Valley, and up and over the Sierra Nevada mountains.


The thin, rod-like structures in the wings of insects that provide structural support to the wings. The front edge of the forewings contains the strongest and most important vein in the wings since this edge of the wing is responsible for producing the motion needed to create the lift needed for flight. Wing venation patterns can be key means of identifying taxa.


The underside of an insect’s body. In butterflies, the ventral surface is visible when the wings are held closed over the body. In humans, this is equivalent to the “front” side of our bodies.


Rocks and soils that are produced from eruptions or upwelling of molten or super-heated rocks or ash from deep within the earth to the surface (“igneous”). These soils can be found around the large, cone-like volcanoes of the Cascade Mountains of the Pacific Northwest, or in long fissures in the earth like the eastern edge of the Sierra Nevada. In this study, Castle Peak is composed of eroded volcanics and petrified mudflows associated with volcanic eruptions.


The description of how many broods (generations) per year a particular butterfly species produces at any one location. A butterfly with one generation per year is “univoltine”. Butterflies with two generations per year are called “bivoltine” and those with more than two are generally referred to as “multivoltine”.


A general term for organisms that are typically associated with habitats that are disturbed by human activities or are dominated by non-native, invasive plants.


The total distance between the tips of the forewings when the wings are held open with the hind margins at right angles to the long axis of the body.