Tag Archives: Bonn

An iridescent pendant made with beetle’s elytra

By Adriana E. MarvaldiCONICET/División Entomología del Museo de La Plata, Argentina

The beetles, insects of the Order Coleoptera, are distinguished by the presence of elytra. This is the fundamental feature that defines the largest and most diverse group of animals on Earth (Lawrence and Newton 1982). The elytra (singular, elytron) are the hardened, sclerotized fore wings, evolutionarily modified as a protective case that covers the hind wings (those used to fly) and dorsum of the abdomen when at rest. The beetles and their elytra come in all sorts of shapes, sizes, textures, and colors. Many species of beetles, from several different families, look like jewels because of their iridescent structural colors, a visual phenomenon resulting from the interaction of light with the nanostructures of the integument that changes color according to the viewing angle (Seago et al. 2009; Saranathan et al. 2015). No wonder that in so many cultures, of all times and all around the world, iridescent beetles and their parts are integrated into ornaments full of beauty and symbolism.

For an entomologist, with a special interest in beetles, a set of dozens of sparkling, green elytra assembled into a strip immediately catches the eye. An object like this was noticed, rather unexpectedly, leaning on a shelf of the archaeological-ethnographic collection of the Americas at BASA-Museum of Bonn. The cultural and natural environments from which it comes were intriguing and to figure them out would require some research. At first sight, it had no tag attached, but a closer look revealed the inventory information written in the underside of one elytron (BASA Inv.-No. 5724). In the Museum´s inventory Book the number led to a succinct description of the object: “Ketteanhänger aus Insekten Panzern mit Federn (rot/gelb) am Ende” [Chain pendant made of insect armor with feathers (red/yellow) at the end]. In the last column, the object is attributed, with doubts, to the collection “Jankausky (?)”.

Located on another shelf, a few steps away from the drawer holding the pendant made of beetle’s elytra, there it was an entire beetle exemplar, exhibited as an object with an inventory tag attached to one of its legs (BASA Inv. –No. Hm35). A giant insect of more than 60 mm long and 25 mm wide, with iridescent integument showing hues from green to purple particularly in the elytra. Its shape and general aspect indicated with certainty its membership to the Buprestids, a family of Coleoptera which are commonly called “jewel beetles”. Observation of additional details suggests it is the species Euchroma gigantean (Linnaeus), a wood borer beetle inhabiting the Neotropical rain forests, and considered the largest buprestid of South America. Without further collection data, a direct link of this “object” with the previous one could not be established. But it was tempting to do an association because, as it will be explained later, beetles of this species are among the main sources of the gleaming elements that people from the Amazonian lowlands use to create ornaments.

The characteristics observed in object No. 5724 indicate it is one of the typical ear pendants made by the Jivaroan people (e.g., Shuar and Achuar) from the Amazon lowlands between Ecuador and Peru (Rivers 2003; AMNH 2017). People from the Amazon Basin are known for their variety of personal ornaments that they wear for special occasions, made with materials taken from their natural environment, like colorful bird feathers, little stones, seeds, plant fibers, and iridescent beetle elytra. The wing covers (elytra) of two different beetles have been documented to be used in the elaboration of their ornaments: Euchroma gigantean (Linnaeus) from the family Buprestidae and Chrysophora chysochlora (Latreille) from the Scarabaeidae. In object No. 5724 from BASA, the elytra from its upper part are longitudinally striate, greenish shimmering purple and gold, and longer and more flat than the elytra strung on the rest of the pendant, which are shorter, apically more curved, and strikingly sparkling green colored with a thickly punctuated texture. The former elytra are most likely from buprestids, and the latter, from scarabs.

This was a short story about a lucky day for a coleopterist visiting an ethnographic collection. In the end, it looks like the elytra are meant to provide beauty and protection, not only to the beetles.

References

AMNH. 2017. Beetle-Wing Body Art: Shuar Ear Ornaments. https://www.amnh.org/explore/news-blogs/from-the-collections-posts/beetle-wing-body-art-shuar-ear-ornaments.

Lawrence, J F & Newton, Jr. AF. 1982. Evolution and Classification of Beetles. Annual Review of Ecology and Systematics, 13 (1): 261-290.

Rivers, VZ. 2003. Emeralds on wings: Jewel beetles in textiles and adornment. Pp. 163-174. In Motte-Florace, E. and Thomas, J. M. C. (Eds.) Les ‘insectes’ dans la tradition orale/ Insects in oral literature and traditions. Paris: Peeters.

Saranathan V, Seago AE, Sandy A, Narayanan S, Mochrie SGJ, Dufresne ER, Cao H, Osuji CO, Prum RO. 2015. Structural diversity of arthropod biophotonic nanostructures spans amphiphilic phase-space. Nano Lett. 15, 3735-3742 (doi:10.1021/acs.nanolett.5b00201).

Seago AE, Brady P, Vigneron J-P, Schultz TD. 2009. Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera). J. R. Soc. Interface 6, S165-S184 (doi:10.1098/rsif.2008.0354.focus).