The secret of how caterpillars tame ants

The secret of how caterpillars tame ants

Researchers in Bengaluru use MicroCT scans to understand how predators turn protectors

Scientists from the National Centre of Biological Sciences (NCBS) in Bengaluru have got fascinating insights into the relations of caterpillars and their ant hosts using advanced X­ray MicroCT technology. The intriguing caterpillar­ant associations have been a subject of study for decades. Butterflies of the family Lycaenidae, known as Blues and Hairstreaks, have over millions of years evolved a range of adaptations that have tamed their ferocious ant predators into protectors and providers. In fact, caterpillars of this family closely associate with ants, becoming strange bedfellows. Not only do ants not eat these caterpillars and pupae, they actually care for them and aggressively protect them from other predators and parasitoids, thus creating an enemy­free space for the butterfly’s early stages. The study using X­ray MicroCT technology describes the association between ca

terpillars of the Lilac Silverline Apharitis lilacinus butterfly and cocktail ants. This butterfly was rediscovered in India a few years ago after a gap of almost 100 years by a student Nitin Ravikanthachari. This species has an obligate association with a single species of cocktail ant called Crematogaster hodgsoni. Scientists who have been studying the relationship between the two species, found that females of the Lilac Silverline deposit eggs at the entrance of cocktail ant nests, sometimes on sand and away from plants. Caterpillars are completely dependent on the ants after hatching from eggs, and they are constantly attended by their hosts. The caterpillars live inside the ant nests, often among the ant broods, and are cared for by the tending ants just like the rest of their own brood. While the presence of the ant­associated organs in these caterpillars and their relative development with respect to the nature of ant associations is well known, the functional morphology

of these organs has been poorly understood. This was because these organs get destroyed in traditional methods of dissection and staining. Dipendra Nath Basu, a PhD student under Dr. Kunte turned to X­ray microtomography, or MicroCT to shed light on the functional morphology of the ant­associated organs.  The organs of caterpillars primarily studied by the scientists are called dew patches in some species and nectar glands in others. These organs produce carbohydrate­rich secretions to attract and reward the tending ants. For the most part, these sugary secretions, which ants drink readily, keeps the ants interested in tending and protecting the caterpillars.