Classification Hierarchy

Class:  Insecta  (insects)
  Order:  Lepidoptera (butterflies and moths; insects with scaly wings)
    Superfamily:  Papilionoidea  (true butterflies)
      Family:  Nymphalidae  ("brush-footed butterflies")
        Subfamily:  Danainae ("Milkweed butterflies;"  157 species worldwide)
          Genus (plural:  Genera; adjective:  Generic):  Danausplexippus
              Author and year species was described:  (Linneaus, 1758)

Aposematism (adj.: aposematic): "warning coloration" of an inedible insect, like the monarch, to "advertise" this fact to potential predators; after the first unpleasant experience (see "Emetic Unit") the predator learns to avoid this and other similar appearing prey (see "mimicry").

Asclepias: One of the genera of milkweeds, with about 108 species in North America; 15 species are described for California; foodplant of the monarch caterpillar.

Asclepiadaceae: scientific name of the milkweed plant family.

Autumnal Site (or "Roost"): formerly "temporary site," a site that does not persist through the winter, usually characterized by its small size. It is often not used each year and may or may not have a long history of use. The terminology was changed from "temporary" as the latter often means used once and not again, while "autumnal" implies use each autumn.

Bivouac: a temporary Roost (q.v.) of adult monarchs en route to an "Autumnal" or "Permanent" Overwintering Site (q.v.)

Butterfly Tree: common term for monarch roosting trees in California Overwintering Sites (q.v.)

Cardenolides: bitter, distasteful heart-poison compounds (cardiac glycosides) found in many but not all species of milkweed; causes predators, such as birds, that eat insects containing cardenolides to retch and vomit, otherwise capable of causing death. See "Sequestration" and "Emetic Units."

Danaus plexippus (always underlined or italicized, with a capital "D" and small "p"): scientific name of the monarch butterfly.

Emetic Unit: an amount of Cardenolide (q.v.) sufficient to cause one Bluejay to vomit.

Fingerprinting: chemical analysis to characterize the relative composition and concentrations of various Cardenolides (q.v.) unique to a given species of milkweed and/or to a monarch butterfly whose larva sequestered (q.v.) these compounds from that species of plant. A technique to track monarch migration: "fingerprinting" an adult monarch can indicate where that individual originated, particularly if its larva fed on a species of milkweed of limited geographic distribution (e.g., a monarch found in Minnesota may have developed on a species of milkweed found only in Louisiana, hence it must have flown from Louisiana to Minnesota).

Hair Pencils, Hair Brushes: paired eversible (protrudable) scent-distribution brushes, usually concealed in the abdomen; can be inserted into the "Scent Pouch" to pick up chemicals ("Pheromones" q.v.) manufactured or stored there.

Life Cycle: as in a vast majority of insects, the monarch undergoes "complete metamorphosis" (development), consisting of four distinct stages: Egg, Larva (or Caterpillar), Pupa (or Chrysalis), and Adult. Monarch larvae feed on the leaves (and sometimes flowers and seed pods) of milkweed plants, while adult monarchs feed by sucking nectar through their coiled Proboscis (or Tongue). Transformation from the Larva to the Adult takes place in the Pupa. There are several generations of monarchs each year.

Mass Movement: large number of individuals traveling in one direction, a common phenomenon in insects (e.g., Painted Lady butterflies "migrate" through southern California about once a decade; "Migratory" Locusts. Frequently called "Migration" (q.v.).

Migration: loosely, the movement of individuals from one place to another (see "Mass Movement"); strictly, the back-and-forth movement of individuals on a regular basis (e.g., many northern hemisphere birds migrate south in the fall and north in the spring). The monarch butterfly is thought to be the only "true" migratory insect, in that most individuals of at least one generation undertake an annual back-and-forth flight (from eastern North America to Mexico, or from western North American to the California coast and Baja). The return flight to or toward the birthplace is often called "Remigration."

Milkweed: a plant of the Milkweed Family ("Asclepiadaceae"); most have a milky sap and are frequently but not always loaded with toxic and bitter chemical compounds ("Cardenolides," q.v.) that repels insects and other herbivores that would otherwise feed on the plant; the monarch is one of a handful of insects and other animals that have evolved the physiological means to overcome this potent defense (see "sequestration').

Milkweed Butterflies: the subfamily Danainae of the family Nymphalidae; 157 species worldwide, in 11 genera, of which the monarch butterfly is one species. There are two milkweed butterfly species in the U.S.; the second is the Queen, Danaus gilippus. They may feed on plants in the Milkweed family, hence their common name.

Mimicry: concept that an edible species of insect (the "Mimic") is avoided by predators because it can not distinguished from another similar-appearing but inedible species (the "Model") of insect; classic case involves the inedible Monarch model and its edible Viceroy mimic (See "Aposematism"),

Batesia n Mimicry: a predator learns to avoid both species only after attacking the model; this system is supposed to work because the model s are more abundant than the mimics, but this point is currently being debated. The"classic" example of the Monarch-Viceroy Batesian Mimicry is apparently NOT the case. It has been recently discovered that the Viceroy is also inedible, thus making the Monarch-Viceroy an example of Mllerian mimicry.

Mullerian Mimicry: different species, sometimes quite unrelated to each other, are all mimics to each other; the theory is that a predator learning to avoid any of the species simultaneously learns to avoid all others that look like it.

Automimicry: ("auto" prefix = "self"; also called Browerian Mimicry): concept that even though some individual monarchs are edible (their larva fed on a species of milkweed lacking Cardenolides [q.v.]), they are nevertheless prot ected from predators because they mimic the usually more abundant inedible model monarchs whose larvae did feed on Cardenolide containing milkweed.

Another form of automimicry is where a freshly emerged adult monarch is inedible and serves as a model but loses its toxicity through time and becomes a mimic to other younger fresher adults.

Oyamel: common name of the fir trees (Abies religosa) which serve as the principal roosting tree for monarchs in Mexico.

Permanent Site (or "Roost"): a site that persists through the winter; it is typically a large site that is used year after year.

Pheromones: chemicals released by an insect to influence the behavior of other individuals of the same species. Pheromones derived from pyrrolizidine alkaloids (q.v.), or PA's, are used by at least some male milkweed butterflies (but not the monarchs, an exception) as an aphrodisiac during courtship; see "Hair Pencils," "Pyrrolizidine Alkaloids," and "Scent Pouch."

Pyrrolizidine Alkaloids (Pas): bitter and toxic compounds, odorless to humans, found in many plants, but not in milkweeds. Adult butterflies and moths (especially danaines, ithomiines, and ctenuchine or arctiid moths) seek out and ingest these compounds; they serve as precursors for the biosynthesis of male pheromones (q.v.) and/or as an additional (or only) source of chemical protection from predators.

Rape: describes the mating behavior of monarchs; lacking the pheromone (q.v.) aphrodisiacs of other milkweed butterflies, monarchs forego the more subtle courtship behavior of other species.

Remigration: the return flight from an overwintering site to/toward the summer breeding grounds. See "Migration."

Recovery: (a) recapture of a "Tagged" (see Tagging q.v.) monarch; (b) the rehabilitation of a degraded habitat to a more original, "natural" condition; (c) restoration of a threatened or endangered species to a level of health and abundance so that rigorous protection measures are no longer required.

Roost: a communal aggregation of adult monarchs; may be short or medium term ("Autumnal Site" or "Bivouac" q.v.) or long term ("Permanent Site"). See also "Overwintering Site."

Scent Pouch: a pocket (a type of Alar Organ") on a vein (vein Cu2) of male (only) monarchs (and thus an easy method of distinguishing the sex of an individual); contains specialized scales whose function is not yet clear for the monarch, although most likely somehow involved in chemical defense and/or the production/dissemination of Pheromones (q.v.), as in related milkweed butterflies.

Sequestration: the internal process whereby a caterpillar feeding on a toxic plant is able to shunt the poisons out of the normal metabolic pathways, and "sequester," or store them in the body (as opposed to excreting the poisons or converting the poisons to non-toxic forms). Monarch larvae sequester cardenolides, which are subsequently incorporated into the body of an adult monarch.

Tagging: placing a numbered adhesive label on the leading edge of the forewing of an adult monarch, then releasing the "tagged" individual; the place and date where this is done is recorded. by knowing the place and time of any subsequent "recapture," scientists can determine the minimum distance, minimum time, and most direct compass direction flown, thus learning more about both migratory and sedentary behavior. Analogous to "bird banding" (a numbered or colored ring on the leg), for the same purpose.

Sometimes the tags are placed on the underside of the hind wings so that the tags can more readily be seen when the monarchs are roosting in the trees.

Temporary Site: (now referred to as an "Autumnal Site" q.v.)