Of all the parameters that the scientists studied for the large blue butterfly, one stood out as a critical factor in the decline of the butterfly population. That parameter was the larval mortality inside the ant nests. In other words, too many caterpillers were dying inside the ant colonies and not enough of them were making it into adulthood as a butterfly.
What caused caterpillers to die in the ant nests? To answer this, we must first understand that there were five Myrmica ant species present in the study sites. Of those five, only one species, Myrmica sabuleti served as a good enough host to sustain the large blue butterfly population. The survival of a caterpiller was 5.3 times greater when it was hosted in a Myrmica sabuleti nest than in the nests of the other four Myrmica species.
