(ANSA) - Florence, October 9 - Researchers digging for the remains of Leonardo da Vinci's model Lisa Gherardini Del Giocondo, known as Mona Lisa, said Tuesday that one of the most important burdens of proof lies with the insects found in the tomb. "The dirt that has deposited inside the skull could contain a particular insect that colonizes tombs and helps indicate the age of remains," researcher Stefano Vanin said. Known as the sarcophagus flies, the insect's life cycle helps forensic entomologists determine when an individual died, Vanin said. Researchers have been digging in the basement of a former Ursuline convent in central Florence for months where they believe Mona Lisa was buried. La Gioconda - as the Italians call the Mona Lisa because of the surname of her husband, del Giocondo - is believed to have joined the Ursuline nuns in old age.