Palearctic, Nearctic, Oriental, Neotropical, Australian, Oceanic Islands:
Danaus plexippus ranges from North
and South America and the Caribbean to Australia, New Zealand, the
oceanic islands of the Pacific, Mauritius, the Canary Islands of the
Atlantic, and, most recently, Western Europe.
Physical characteristics: Adults
of both sexes are bright orange with black borders and veins.
Food habits: The larva feed on a
wide range of milkweeds of the genus Asclepias. From these plants
they acquire and store cardiac glycosides, secondary plant compounds
that protect them from predation. The adults of the species forage
for flower nectar.
Reproduction: The mating period occurs
in the spring, just prior to migration from the overwintering sites.
The courtship of D. plexippus is fairly simple and less dependent
on chemical pheromones in comparison with other species in its genus.
Courtship is composed of two distinct stages, the aerial phase and
the ground phase. During the aerial phase, the male pursues, nudges,
and eventually takes down the female. Copulation occurs during the
ground phase and involves the transfer of a spermatophore from the
male to female. Along with sperm, the spermatophore is thought to
provide the female with energy resources that aid her in carrying
out reproduction and remigration. Once they reach their breeding grounds,
the females lay their eggs on milkweed host plants. The egg and larval
period is temperature dependent and lasts about 2 weeks. At the end
of this period, the larva enter a period of pupation, and after 9
to15 days an adult butterfly emerges.
Behavior: Like birds, D. plexippus
follows a pattern of seasonal migration. There are two distinct populations
in the North America, those that breed in the East and those that
breed in the West. Each autumn millions of these butterflies leave
their breeding grounds and fly to overwintering sites. The Eastern
population overwinters in the volcanic mountains of eastern Michoacan
in central Mexico. The Western breeders spend their winters along
the California coast. Similar migratory behavior has been observed
in Costa Rican and Australian populations.
Habitat: D. plexippus is a predominantly
open country, frost intolerant species whose range of breeding habitats
is greatly dependent upon the presence of asclepiad flora (milkweeds).
The monarch requires dense tree cover for overwintering, and the majority
of the present sites in California are associated with Eucalyptus
trees, specifically the blue gum, Eucalyptus globulus. These trees
were introduced from Australia and have filled the role of native
species that have been been reduced by logging.
Biomes: temperate forest & rainforest,
temperate grassland, chaparral, tropical rainforest, tropical deciduous
forest, tropical scrub forest, tropical savanna & grasslands,
Status: special concern
The annual monarch migration is considered a "threatened phenomena"
by the International Union for Conservation of Nature and Natural
Resources. Steps have been taken by both the United States and Mexican
governments aloge with numerous private individuals and organizations
to protect the overwintering sites of these butterflies.