In her thirties, she published two books of engravings of moths, butterflies, and their caterpillars, with accompanying descriptions. Then, in her fifties, she traveled with her daughter to Dutch Suriname to study insects there, in 1705 publishing "Metamorphosis insectorum surinamensium," a collection of 60 engravings, each showing a tropical insect in its full life cycle along with the native plant on which it lived. The work is widely regarded as her masterpiece.
All along the way, Merian racked up a series of remarkable firsts. She was the first European naturalist – male or female – to undertake an independently financed expedition to the New World. She was arguably the first naturalist trained in the fine arts to study a specific type of organism for a sustained period, and one of the first to depict tropical species in their natural colors.
As Gettysburg College biologist Kay Etheridge argues in a 2011 article, she may have been the world's first ecologist, that is, the first person to document the interactions between different species, emphasizing what we would today call the food chain. You could even make the case that she was the first female biologist of the modern era.
Indeed, Merian was a member of one of the first generations in the West to take seriously the concept of empirical observation. It was only during her lifetime that a consensus among scholars began forming around the concepts of experimentation, repeatability, and peer review. As Los Angeles Times art critic Holly Myers noted in a 2008 review of a Merian exhibition at the Getty Museum, her era was one of upheaval "which saw science, religion and art locked in a state of muddled and sometimes violent agitation."