Weekword=Yellow

I love the opportunity to think about colors, in particular how pigments originate, their history of use, their biochemical properties, functions in nature, and thinking about how lovely they make our visual world.

Here's just a few little random jabberings about yellow:


Yellow is considered one of the warning colorations in biological organisms called aposematic coloration. Organisms use these warning colors to communicate that they are poisonous, sting, are toxic, or are in some other sense "dangerous". Bees, wasps, and other members of the hymenopteran family of insects are well known for using these colors to warn potential predators not to mess with them. If you've noticed that several types of bees and wasps, for example, look similar to each other, this is a form of mimicry called Mullerian mimicry.Other insects however that do not have a stinger also use this coloration to fool potential predators into thinking that they too are nasty characters-this is called Batesian mimicry.

Hover fly-an example of Batesian mimicry, they are not dangerous, and can be recognized as  from bees because they only have one pair of wings. They are excellent flower pollinators!

blister beetle-secrete a blistering agent called cantharadin as  a defense mechanism

Poison dart frog from from Central America-use a lipophilic alkaloid toxin as chemical defense. 

Leopard Lacewing Butterfly caterpillar from Singapore using warning coloration to warn of their foul taste.

Biological yellow pigments are produced from carotenoids, separated into two main types xanthophylls and carotenes. Most animals are incapable of synthesizing these pigments, relying on their diet to obtain them, however there is an aphid that has been able to replicate a form of these pigments from a fungus through horizontal gene transfer. Xanthophylls, typically yellow in color, are responsible for the yellow in egg yolks and are primarily in green leaves (xantho- greek for yellow and phyll - greek for leaf).

Yellow ochre (hydrated iron (III) oxide is one of the oldest mineral pigments in the world, derived from natural clays containing mineral oxides, and used on papyrus from Egypt dated from around 1550 BC.

Indian yellow is said to have originally derived from dried urine of cows who've eaten mango leaves. It is synthetically produced these days and is known as magnesium euxanthate.

The ancient Mayans associated the color yellow with South. The glyph also means precious or ripe.

Hope everyone has a wonderful rest of the weekend and hopefully I'm not too terribly late :) Please visit Erika at Hub 52 for more Weekwording folks posts.