Ricardo Pérez-de la Fuente was holding up a piece of ancient amber, peering inside at the 40 million year old insect. The fierce-looking larva was a favorite, preserved entirely after being trapped in a sap that hardened over millennia: its image adorned its desktop computer.

"Seems like a bug, almost — full of spikes," said Pérez-de la Fuente. He then added: "They 're going back."

Pérez-de la Fuente, a postdoctoral fellow in Harvard and expert in fossilized insects, stood that late May day in the Northwest Laboratory 's basement, near one of the many cabinets housing the 50,000 to 60,000 fossil insects in the paleoentomology collection of the Museum of Comparative Zoology. He had pulled out a drawer holding hundreds of insects in repayment of a long-forgotten loan to be returned to Germany.
Charles T. Brues, Harvard's instructor on economic entomology, borrowed the specimens from Königsberg University in what was then East Prussia in 1934. Why Brues never handed back the specimens remains a mystery. Less turbid is that the parent amber jewellery collection 's fate has been swept up in World War II's maelstrom and that some of the loaned fossils have been spared devastation while sitting across an ocean in the MCZ specimen cabinets.
The discovery of the loan — and the return of 383 specimens to Göttingen University, which oversees the remnants of the Königsberg Amber Collection — is the fruit of the work of Pérez-de la Fuente over the past four years, and stems from Professor Brian Farrell's convictions. The Harvard biologist believes that the digitization of museum collections is an significant step for researchers around the world to open up science and encourage new work.
Farrell, the faculty curator of the entomology collection and an expert in the dizzying array of beetles around the world, has directed the digitization of the MCZ's larger collection of insects — 7.5 million specimens — since the mid-1990s, when he obtained a grant from the National Science Foundation to picture the collection 's type specimens for some 33,000 species.
The museum went through the tedious process of shooting photographs on slide film as the project began, and then scanning the slides to digitize the pictures. After then the rapid advancement of imaging technology has improved, Farrell said, but progress has been slow, with so many specimens in the collection.
In 2013, Farrell won another NSF grant and took Pérez-de la Fuente to oversee fossilized insect digitization, including 10,000 trapped in amber pearl jewelry. Three years later, Alexander Gehler, curator for the Geoscience Museum at the University of Göttingen, wrote to inquire about the long overdue loan and to ask for the borrowed fossils back.

The specimens are of Baltic amber, formed tens of millions of years ago when vast pine forests full of insects covered Northeastern Europe, some of which became trapped in resin. The sap hardened into a smooth, yellowish block, preserving the insects which collectors and scientists were to discover and examine.
Pérez-de la Fuente said that the layer of Eocene amber reaches into the Baltic Sea. Because amber floats, pieces periodically wash ashore. By the mid-1930s the Königsberg University had acquired some 100,000 pieces of amber Jewellery collection. Before his death in 1955 the specimens that Brues borrowed contributed to many scientific publications.