The discovery published in the international scientific journal Papers in Paleontology states that this method of fossilisation is extremely rare and normally the skeleton of these insects rapidly decomposes since it has a chitinous composition, which is an organic compound.

“The degree of preservation of these bees is so exceptional that we were able to identify not only anatomical details that determine the type of bee, but also their sex and even the supply of monofloral pollen left by the mother when she built the cocoon”, points out Carlos Carvalho's grandson, a paleontologist at Naturtejo Geopark.

Carlos Neto de Carvalho says that the project identified four paleontological sites with a high density of bee cocoon fossils, reaching thousands in a square measuring one meter.

These sites were found between Vila Nova de Milfontes and Odeceixe, on the coast of Odemira (district of Beja).

“With a fossil record of 100 million years of nests and hives attributed to the bee family, the truth is that the fossilization of its user is practically non-existent”, reads the note.

According to the Naturtejo Geopark, these cocoons produced almost 3,000 years ago preserve, like a sarcophagus, the young adults of the Eucera bee that never saw the light of day.

This is one of about 700 species of bees that still exist in mainland Portugal today.

Understanding the ecological reasons that led to the death and mummification of bee populations nearly 3,000 years ago "may help to understand and establish resilience strategies to climate change".

“A sharp decrease in night temperature at the end of winter or a prolonged flooding of the area outside the rainy season could have led to the death, by cold or asphyxiation, and mummification of hundreds of these small bees”, reveals Carlos Neto de Carvalho.

The Naturtejo Geopark of Meseta Meridional, which is part of the UNESCO world network, includes the municipalities of Castelo Branco, Idanha-a-Nova, Oleiros, Penamacor, Proença-a-Nova and Vila Velha de Ródão (in the district of Castelo Branco) and Nisa (Portalegre).