Foster Care
Introduction
The large blue butterfly, Maculinea arion, knows how to fool ants into raising their caterpillars. But when the ant, Myrmica sabuleti, disappear there survival is at stake, a study has shown. The butterfly lays eggs on thyme flowers and the caterpillars fall on the ground after hatching. Thanks to a chemical caterpillars secrete, ants mistake them for their own ones, and take the caterpillars to their nests and protect them. When farmers stopped grazing livestock in the English countryside, the vegetation increased and the soil temperature decreased, making it unsuitable for the ant.
With the ants gone, there was nothing to protect the butterfly.
Source
Down To Earth, July 2009