The Brahmins of the "upper caste" is easily represented as there are several creatures with the word in their name. Here is the Brahminy Kite:
See the beauty of the Brahminy Skink:
There is also the Brahminy Myna with its very "brahminical" tuft on the head!
Kshatriyas or Warriors: I am reminded of fierce warriors when I see ferocious predators such as the Dragonfly, which pounces on its prey and munches it up.
Here is the Common Picture-wing, another kind of Dragonfly:
Some of these predators are aptly named. Here is the Robberfly:
Another warrior is this Spider Wasp, seen here stunning and dragging a Yellow-thighed Tarantula to her nest, where she will deposit the paralyzed spider, and lay her eggs, ensuring fresh meat for the newly-hatched eggs. She will never see her children, but takes so much trouble for their future.
Vysyas or Traders: Several plants have a "trade" arrangement with insects, and one of the most interesting of them are the Ceropegias, which trap the insect inside the flower when it enters for nectar, and releases it after it is coated with pollen dust ensuring pollination.
Sudras or Scavengers:
The Long-billed Vulture eats (and thus disposes of) carrion and dead meat...a valuable function of waste management.
Here is the scavenger, majestic in flight:
Dung Beetle. In Nature, there is no "s*it"...everything is a nutrient, and the creatures who use it are many! This beetle rolls the dung along with her back legs into a suitable hole in the ground, and then lays her eggs on it, so that there is enough nutrition for the newly-hatched larvae.
Blister Beetle, the Untouchable...because touching it causes it to extrude a secretion that causes blisters on our skin.
So, if we like, we can drag casteism into the rest of the animal kingdom, too! But I'm hoping we will all realize that our wildlife is not "varna, bu "suvarna" or gold...a treasure that we must protect and cherish.