Monarchs are easily distinguished from all other butterflies in BC, through a combination of their unique colour pattern and their large size. Males have a black sex patch on each hindwing; females do not.
Eggs are conical, with ridges down the side, and are green white or cream. Mature larvae are ringed with alternate black, yellow, and white stripes. On the 3rd and 12th segments are two long, black, fleshy tendril-like horns. The prolegs are black and there is a large white spot at the base of each one. The pupa is cylindrical and bright green, with an oval gold spot on each side of the antennae. A row of 11 gold spots circles the lower part of the pupa; there is a second row of gold spots above it, with a black line along the top of the row (Saunders 1869c). A line drawing of the pupa with terminology for spots is provided by Urquhart and Tang (1971).
None. The type locality of the species is "Pennsylvania."
The name Danaus is linked to the Danai, the name Linnaeus gave to a group of butterflies primarily composed of present-day Pieridae and Satyrinae. Danaus was the name of the king of Argos, after whom the Argives and often the Greeks as a whole were called Danai ("children of Danaus") by Homer (Emmet 1991). The common name "royals" is used here for the first time, because there is no existing generic common name.
Three royals are found in the USA and Canada: the Monarch, the Queen, and the Soldier. All are large orange brown butterflies with black markings. Only one species, the Monarch, occurs in BC.
Monarchs are multivoltine in southern North America, and migrate north into low-elevation areas of southern BC each summer. The Monarch's larval foodplant in BC, showy milkweed (Asclepias speciosa), is the only milkweed native to BC and occurs in the dry areas of the Southern Interior of BC. When fourth instar larvae collected on showy milkweed near Keremeos in late June were reared, adults emerged in mid-July (CSG). Many species of milkweed have been recorded as larval foodplants outside BC, as summarized by Malcolm and Brower (1987).
Monarchs lay eggs on the milkweed and at least one generation matures successfully each summer in BC. The number of adult Monarchs in BC varies from year to year, but the species is generally uncommon. In the late summer and fall, BC Monarchs presumably migrate south to California to hibernate. More than 200 hibernation sites have been recorded along the California coast and Baja California, south from San Francisco. Monarchs now hibernate in stands of introduced Australian eucalyptus trees, as a result of the cutting of the native stands of Monterey pine (Pinus radiata) and Monterey cypress (Cupressus macrocarpa). The hibernation sites in California have little legal protection against destruction, and real estate developments threaten most of them (Crolla and Lafontaine 1996).
Some Monarchs fly further west than normal when migrating north, and end up on the west coast, with the most western record being from Tofino (AGG). Similarly, the eastern North American populations are regularly blown long distances out to sea by strong westerly winds during their southward migration in the fall (Urquhart and Urquhart 1979), resulting in migration from North America to Great Britain (Williams 1949b). Milkweed is not native to the west coast of BC, so normally migrants to that area cannot breed successfully. Monarchs, however, are good at finding very isolated patches of milkweed and using them as larval foodplants (Shapiro 1982d). They move constantly between areas, instead of staying in a patch of milkweed once they find it (Zalucki and Kitching 1985), which increases the probability of finding new patches of milkweed. This occurs regularly on Vancouver Island, where milkweed is grown in many gardens and where gardeners look forward to watching maturing Monarch larvae.
Monarch larvae accumulate and concentrate cardiac glycosides (heart poisons) in their bodies from the milkweed they eat. The poisons are retained in the bodies of the adults, making them toxic to most bird and mammalian predators. Some milkweeds do not contain cardiac glycosides, and the adults are therefore palatable. Some predators can also eat Monarchs without being affected by the cardiac glycosides. The Viceroy is also unpalatable to predators, and both butterflies benefit from its mimicry of the Monarch.
Monarchs are frequently seen in the dry Southern Interior of BC, and infrequently in the Lower Fraser Valley, on Vancouver Island, and in the Rocky Mountain Trench. We have determined that the two map records for northeastern BC in Layberry et al. (1998) are data errors, and are actually Painted Lady records. Monarchs are frequently reared in captivity on potted or garden milkweed plants, and are then released into the wild in areas that normally have few Monarchs. This makes it difficult to determine whether a sighting or capture of a Monarch in an unusual area is that of a migrant or just of a reared butterfly. Monarchs in the Kootenays may be the eastern North American population; those in the rest of the province are part of the western North American population.
The Monarchs in BC are of Special Concern because of destruction of their hibernation sites in California as a result of urban development. In addition, milkweed is considered a noxious weed by the agricultural industry in many provinces, and is sometimes deliberately eliminated (Crolla and Lafontaine 1996). Milkweed is still abundant in the Southern Interior of BC, but may become less common in the future as more land is cleared or as range weed control programs eliminate it.
Monarchs are found in many tropical and subtropical areas of the world. In North America the migratory populations hibernate in CA (western populations) and MEX (eastern populations). They migrate north to central CAN. Monarchs colonized New Zealand about 1840, Australia in 1870, and the Canary Islands in 1880, following the introduction of weedy asclepiads upon which the larvae could feed (Higgins and Riley 1970).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
22/11/2019 1:04:58 PM]
The information contained in an
E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section.
This information is scientifically based. E-Fauna BC also acts as a
portal to other sites via deep links. As always, users should refer to
the original sources for complete information. E-Fauna BC is not
responsible for the accuracy or completeness of the original information.