LAUSR

Calcium carbonate minerals are found in many biological systems starting from Proterozoic [1]. Magnesium calcite is rarely found in animal and only have been observed in some corals [2], coccolithophores [1] and sea urchin tooth [3]. The discovery of Mg-calcite and disordered dolomite on the leaf-cutting ants [4] is the first example in the insect. The leaf-cutting ants are a group of ants in the New World tropics and using fresh-cut leaves to cultivate fungus, which functions as their food source [5]. The decomposition of organic material, respiration, and fermentation in the fungus garden generate a large amount of carbon dioxide. Carbon dioxide concentration in the nest can reach up to 6% [6], which is significantly higher than the current atmospheric level at 400 ppm. Therefore, the appearance of Ca-Mg carbonate might have been a response to the combination of biotic and abiotic pressures.