Colias is a genus of butterflies in the familyPieridae. They are often called clouded yellows in the Palearctic and sulphurs (a name also used for other coliadine genera) in North America. The closest living relative is the genus Zerene,[4] which is sometimes included in Colias.
Wing venation
This genus occurs throughout the Holarctic, including the arctic regions. They are also found in South America, Africa, China and India. Their caterpillars feed on certain Fabaceae, for example vetches (Vicia). The adults forage for nectar.[5] most are thus beneficial by keeping weeds at bay, some occasionally become nuisance pests on crops like alfalfa. In some species, the wings of males have brilliant ultraviolet reflection, while those of females do not.[6][7] Adults of both sexes have various colour forms. Males are particularly conservative based off of their genitalia structures. These structures are difficult to identify making it difficult to classify the Colias.[8]
Most if not all species of this genus, as usual for Coliadinae, do not sequester toxins or other noxious compounds from their food plants. They are therefore a well-loved prey item of insectivores as compared to Pieris of the related Pierinae. They make up this disadvantage by being more nimble and better able to evade attacks by would-be predators.[9]
Hybridization runs rampant in these polytypic and clinal[10] butterflies, confounding molecular phylogenetics studies. In general, cladistic analyses of only one type of data (particularly mtDNAsequences) cannot be considered reliable. Regardless, the evolutionary distance within some "species" is so large that cryptic speciation rather than (or in addition to) interbreeding seems to be the cause. For example, the Beringian populations traditionally assigned to the northern clouded yellow (C. hecla) could warrant recognition as a species; hybridization between North American and Asian populations seems to have played a role in their evolution, but as a whole they appear to be a rather old and distinct lineage.[11]
Thermoregulation
Colias are behavioral thermoregulators. They will move their habitats in order to regulate their body temperature. This leads to them having specific and narrow temperature ranges that they could live in. This leaves the Colias to be extremely vulnerable to climate change.[12] The degree of melanism on their wings and fur thickness are major parts of their thermoregulation. The wing absorption/melanization is determined by the proportions of their coloration. They are in a class of pollinators that require minimum fuel due to their small size.[13] When they need pollen they are attracted to flower patterns in the ultraviolet, similar to themselves.
Flight
Colias spend most of their time in active flight and are very strong flyers. Flying is essential for them mate as well as pollinate. But they are very susceptible to temperature and have flight restrictions based on their body temperature. Flight activity is restricted between 27-40 degrees Celsius. Their flight performance is best once at 33-38 degrees Celsius. In order to maintain these temperatures the Colias will use a lateral basking posture. When they reach a temperature outside of the flight activity zone, Colias will find a shaded area under plants in order to cool down.[14]
Species
The genus Colias has approximately 90 different species. It is often difficult to find differences between the species, since they are mostly identified through their wing structure and pattern.[15]
Colias are usually some shade of yellow, orange or white. Their uppersides feature black borders (usually solid in males, often with pale spots in females). They always perch with wings closed, but upperside pattern may be seen faintly through the wing, or glimpsed in flight.[17]
^Bjorn Petersen, 1963. The male genitalia of some Colias species.Journal of Research on the Lepidoptera 1: 135-156.[1]Archived 2017-06-03 at the Wayback Machine
^Lucien A Berger, 1986 Systématique du genre Colias F: Lepidoptera-Pieridae Bruxelles: Imprimerie des Sciences, 1986.
^Paul C. Hammond, 1990 Patterns of geographic variation and evolution in polytypic butterflies Journal of Research on the Lepidoptera 29(1-2):54-76.
[2]Archived 2013-12-03 at the Wayback Machine
^Brock, J.P. & Kaufman, K. Kaufman Field Guide to Butterflies of North America. Houghton Mifflin, 2003, p. 60.
Further reading
Vladimir Lukhtanov & Alexander G. Lukhtanov, 1994 Die Tagfalter Nordwestasiens: (Lepidoptera, Diurna) V. Eitschberger ISBN9783923807024
Joseph T. Verhulst (English translation R. Leestmans, editing E. Benton and R. Leestmans), 2000 Les Colias du Globe translation Monograph of the genus Colias Keltern, Germany: Goecke & Evers ISBN9783931374150
Glassberg, Jeffrey Butterflies through Binoculars, The West (2001)
Guppy, Crispin S. and Shepard, Jon H. Butterflies of British Columbia (2001)
James, David G. and Nunnallee, David Life Histories of Cascadia Butterflies (2011)
Pelham, Jonathan Catalogue of the Butterflies of the United States and Canada (2008)
Pyle, Robert Michael The Butterflies of Cascadia (2002)
Colias [fr] "Le genre Colias" provides distribution information in French.
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