Many animal species cluster together in social groups, some large, some small, but chaos rarely rules and leaders emerge. In some species it’s the “strongman” that ends up ruling the roost, in others it is the wise old matriarch, but what about our caterpillar friends (or enemies)?
The Forest Tent Caterpillar enjoys group living, as does more than 300 other types of butterflies and moths. This was a fact that I had missed and I had clearly mistaken a large group for an infestation of pests. Mistakes that I’ll probably make again in the run-up to the election next year with a larger and more vocal pest whose groups have morphed into SuperPACs.
The question remains: “How do caterpillars elect leaders.” Is it democratic or what? They’re not too vocal and they’re not very aggressive. Also they are differentiated by occupation in the group? McClure et al asked these tantalizing questions in a recent paper (1).
The authors sat and mulled over the possibilities in their lab in Concordia U and then decided to raise groups of young caterpillars, which were studied after different molts. Food, a nourishing wheat germ mix instead of those dull aspen leaves, was the motivating factor for action. The action being to cross a bridge over water. A caterpillar that got its body length ahead of the throng was rewarded with a paint job on one of its segments. The experiment was repeated with multiple groups for multiple times and the numbers crunched. The results showed that leaders weren’t born, but anyone could lead if they so desired.
Next item on the menu was their motivation to lead the way to the food stash. The hungriest were, of course, the most motivated, but that says nothing about the group dynamic. A single hungry caterpillar does not a leader make.
If less than an eighth of the group were hungry, everybody hung around and shot the breeze in their caterpillar way and refused to go foraging. If seven eighths of them were hungry and well motivated, they tried to go off in all directions at once and chaos ensued. In this case, an overwhelming majority did not lead to successful leadership.
Consensus was more rapidly arrived at if there were large percentages of highly motivated individuals in the group who were prepared to lead, but not to many as this resulted in an uncoordinated rabble. Leaders were happy to hand over their role if another caterpillar arrived to pick up the ball. No sex bias or egos were involved, just a consensus on the general need. Do you suppose that we might learn something from Forest Tent Caterpillars?
- M. McClure, M. Ralph and E. Despland, Behav. Ecol. Sociobiol. 65, 1573, (2011).
