A Close Look at Caterpillars: Maria Merian’s Metamorphosis Meets Modern Science

The following is a post by Cindy Connelly Ryan, Preservation Science Specialist, Preservation Research and Testing Division, and Jessica Fries-Gaither, a 2024-2025 Albert Einstein Distinguished Educator Fellow, Professional Learning and Outreach Initiatives (PLOI) and Informal Learning Office (ILO).

Would you hold an insect? Raise insects in your kitchen? Travel thousands of miles from home to study them? Pioneering 17^th century natural scientist, artist, and engraver Maria Sibylla Merian did just that.

Born in Germany in 1647 and later moving to the Netherlands, Merian spent her childhood wondering about caterpillars, butterflies, and moths. For years she raised the larvae, determined their preferred food plants, and stayed up all night to watch the adults emerge from their pupal chrysalides and cocoons. Her detailed notes and sketches became the basis for several caterpillar books, the first of which was published in 1679. Her work was not only groundbreaking for its scientific content, but also for her innovations in artistic technique, using counterproof printing to create softer images that more closely resembled her original drawings.

In 1699, the intrepid Merian and her youngest daughter boarded a ship to the remote Dutch colony of Suriname in South America. What was the goal of this self-financed and unaccompanied journey? To study and paint the insects of the New World. Pretty radical for a single mother at the time!

Merian’s time in Suriname was cut short by illness, but she brought many specimens back to Amsterdam and continued her work with the help of her daughters and several well-known engravers. In 1705, she published a new book, Metamorphosis Insectorum Surinamensium (Metamorphosis of Surinamese Insects) with large, vibrantly colored illustrations of exotic species that captivated natural history enthusiasts. Some images, like one depicting a bird-eating spider, even sparked controversy over whether such species could possibly exist. The Library has digitized its first edition of Metamorphosis of Surinamese Insects, so readers can examine these spectacular images in detail.

When Jessica Fries-Gaither, an Einstein fellow in the PLOI and ILO divisions, prepared a post for the Teaching with Primary Sources blog, she visited the Rare Books and Special Collections (RBSCD) reading room and viewed the book. Marveling over the intensity of the colors after 300 years, she wondered what materials Merian might have used to create such a vibrant palette.

Enter the Preservation Research and Testing Division. Eric Monroe, head of the scientific laboratory section, and Cindy Connelly Ryan, a preservation science specialist, enthusiastically agreed to collaborate on an investigation of the volume’s colorants. A trans-disciplinary team from PRTD, PLOI, and RBSCD met to examine the book and discuss research questions and goals.

Cindy and Jessica poured over the volume, ultimately selecting six plates for initial testing. Multi-spectral imaging by Meghan Hill (Preservation Science Specialist) and Chris Bolser (Preservation Science Technician) provided the first steps of analysis and led the team to focus attention on two plates for deeper study.

Cindy followed this with non-invasive point analyses of the colorants, permitting many to be identified. X-ray fluorescence provided elemental “fingerprints” of the materials, and reflectance spectroscopy captured chemical bonds’ visible and near-infrared absorption features. Multi-band microscopy revealed details of the paints’ textures, layering, and application techniques. This data, combined with the spectral imaging results, opens a window into the working practices of the painter who colored this volume.

Whether the Library’s copy of Metamorphosis of Surinamese insects was painted by Merian herself, by one or both of her daughters, or perhaps by another artist hired by the purchaser, remains a mystery (so far!) but the attention to detail is superb. The delicate, curvy lines of the engravings show through thin, transparent layers of vivid watercolors, yielding subtle shading effects with just a few materials. For example, the red cherries, which are about the size of a penny, are rendered with the poisonous pigment vermillion applied in matte and glossy layers to model depth, as the image below shows. The caterpillar hungrily advancing up the branch towards the cherries is rendered in at least eight shades of yellow, gold, orange and red, all made from mixtures of just two pigments.

The colorants we identified in this volume, all typical for the period around 1705, were made with a combination of European and imported raw materials. Merian’s paints blend ingredients from multiple continents, much as Merian’s commentaries on the insects’ life cycles merge European scientific approaches with new-world subject matter. For example, the blue butterflies are painted with thin layers of azurite blue, a mineral mined in Hungary and Germany, while the translucent pink and burgundy tones are made from brazilwood, a South American tree first used by European artists in the early 17^th century.

“Collaborating with PRTD has been a highlight of my fellowship experience so far,” says Jessica. “While Merian’s work already has strong connections to K-12 science curriculum, the use of modern analytical techniques to increase our understanding of the materials themselves is an application of science I hadn’t considered. I’m excited to share this real-world case study with students and broaden their understanding of how science and technology can be used in a variety of careers.”

As with any scientific investigation, answering one question leads to a whole host of others. While visiting the Joseph E. Cullman III Library of Natural History to view an English translation of Metamorphosis of Surinamese Insects, Jessica learned that the Smithsonian Libraries and Archives also have a copy of the 1705 edition. In viewing the Smithsonian’s copy, she noticed several differences in color between the two volumes. Are these differences attributable to color choices made by the person doing the coloring, or do they suggest a different artist? Are the colorants used in the same way in the two volumes, or differently?  Are there observable differences due to aging? Further investigation may provide answers.

Jessica and the PRTD team plan to share their findings with multiple audiences. Jessica is working with the Informal Learning Office team to create a research box for The Source, a new creative research experience for young people opening in about a year, which will present Merian’s work in the context of primary sources from her era. PRTD is finishing a formal scholarly report on the findings and will collaborate with ILO on interactive programming in conjunction with The Source.

“This project represents the best of the Library’s capabilities,” said Patrick Hastings, Education Outreach Specialist for the Rare Book and Special Collections Division. “By combining a teacher’s good questions with the answers that cutting-edge technology can provide in the hands of master scientists, the Library has learned a bit more about a groundbreaking naturalist and the process by which her books were created. Following Jessica’s inquiry over the past few months has been really exciting.”

Subscribe to the blog— it’s free! — learn how the largest library in the world preserves the coolest stuff in the world.

Description of image detail of the tarantula was corrected from plate 28 to plate 18 6/18/2025