https://www.scientificamerican.com/article/cave-arachnids-modern-range-matches-ancient-glacier-outline/

The modern-day homes of cave-dwelling arachnids called harvestmen trace the long-gone southern limits of glaciers at the peak of the last major ice age, about 22,000 years ago, recent research suggests. “We can now potentially look at the distribution of this species just to reconstruct this glacial maximum,” says Stefano Mammola, an ecologist at the Italian National Research Council's Water Research Institute. Mammola is lead author on the new work, published last August in the Journal of Zoological Systematics and Evolutionary Research.

Harvestmen, sometimes called daddy longlegs, are often mistaken for spiders. Some large-pincer harvestman species live in cold, humid caves in the Pyrenees, the Alps and the Balkan Peninsula, forming a narrow band across Europe. Mammola and his collaborators compared this range with geologists' models of glacier cover during the last ice age and found the band almost exactly matched the maximum southern edges of the glaciers, with only slight variations.