He also painted them as trainee artists with sketchbooks beside a classical goddess Flora's statue at around 1763 to 1764. The painting was an illusion to landscape, nature, and flowers and a deity for the girls. In this painting, that is in the future, there is an enlightenment sense of discovery and curiosity, of two kids moving forward into a globe of knowledge of nature. The kids are emerging from dark wood, and they are quite different in character. Margaret, on the left, is about to seize a butterfly that is perhaps an emblem of the evanescence and fragility of life. She can't, but still, try to grab it. It is childhood nature to rush into the future, the heedless of danger.
On the right is Mary, the elder girl, who is edging towards maturity. She possesses a wisely, a poise, a coolness maturely sense of restraint. She is more eager, considered to see and study the butterfly as Margaret lunges impulsively towards the butterfly, which is settling on the thistle. That simply shows that life is like a thistle, which will require to be grasped. Also, Mary and Margaret holding hands in gold and silver dresses resemble the butterfly silken’s wings. This picture is also full of Thomas's thrill in the natural world – the air itself, clouds, and leaves. It has that summer evening light and intense enjoyment of childhood itself.
It is almost unbearably lyrical and touching - you can practically feel how Thomas's heart goes out to his daughters in their wonderfully contrived predicament. This great portrait is now at the National Gallery in London. Mary and Margaret had challenging lives. As girls of a fashionable and great painter, they had access to the court and all other high society places. However, they were never going to be welcomed by it. As Mary and Margaret grew up, society regarded them as unmarriageable. Mary got married, but it did not last. The two girls later lived together though Mary descended into mental illness.