Category Archives: Papers

Ants milk honey from ‘cows’

An army of hundreds of ants threads upwards through the branches of a yellow bauhinia as it makes its way towards the target: treehopper babies – known as nymphs– no longer than a thumbnail’s thickness.

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As infamous as ants are for their murderous instincts, the intention of these particular ants, Camponotus compressus, is not belligerent, however. These ants are milkmaids.

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Only instead of cows they milk treehoppers, which coincidentally are also known as ‘cowbugs’: Oxyrachis tarandus.
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Cowbug nymph                                              Cowbug adult

The ant, like the graceful and delicate suckle of the milkmaid’s palmed grasp, first strokes the nymph with its antennae. Coaxed by this gentle stimulation, the nymph secretes – or rather excretes – a succulent drop of translucent honeydew through its posterior end that the ant, given its sweet tooth, ravenously drinks up.

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In return for the treat, the grateful ant renders its services to the cow-bug both, as a housemaid, continually cleaning it; and, more importantly, as a fierce body guard.

beatle Ants attacking a beetle and thus protecting the treehoppers from their predator

Our recent paper published in the journal Current Science, delves into this Quid pro quo mutualistic interaction between ant and nymph.

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According to the study, the foraging activity of the ants, which ostensibly appears to be frenzied and chaotic given their prodigious numbers, is actually governed by a congruent precision. Indeed, it is observed that the same ants keep returning every day to the same cluster of nymph treehoppers thus exhibiting high fidelity to a patch of nymphs.

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Ants visiting a patch of treehopper nymphs

Of course, the reader would shrug his shoulders and say: ‘So what?’ Ants are after all known to secrete pheromones that other ants could follow to reach the same destination every day.

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But these ants, unlike most other ant species, do not pave the route between nest and food with chemical ‘bread crumbs’.

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So, how do they, do it? How can these ants, no different from the dutiful milkmaid, tread the long distance from their nest to the same cows day after day? Although the answer to this question is beyond the scope of the study, we, nonetheless, hint at plausible answers.

For details, here is the paper:

Palavalli Nettimi, R., and Iyer, P. (2015). Patch fidelity in Camponotus compressus ants foraging on honeydew secreted by treehoppers. Curr. Sci. 109, 362–366.

Note: Text for this story was originally written by Mr. Somendra Singh Kharola, published in “In this issue” page of Current Sciencehttp://www.currentscience.ac.in/). It is published here (with a few changes) with kind permission from the executive secretary of Current Science, Dr. G Madhavan, and Mr. Somendra. I thank both of them.

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