Ant Rafts

During the recent heavy rains several “fire ant rafts” were found floating in flooded areas at Camp Salmen. These were apparently the result of too many mindlessly obedient Red ants (Solenopsis invica) suffering from the bad decision-making of their ant queens who chose poor locations to establish colonies. It seems an individual ant could sometimes use a little skepticism to keep themselves out of this kind of trouble but, unfortunately, they’re “social insects” and just can’t help themselves. 

 

Most of us know enough to not stick our hands into these rafts to try to help these poor ants; they are not likely to be very grateful.  It’s imagined these scenes are of typically brutal ant behavior where it’s every ant for himself; crawling over one another, trying to desperately grab a gasp of air before being shoved down by their fellows, their number slowly dying of exhaustion and falling away. Nothing could be further from the truth. The ants know exactly what they are doing and are helping themselves with a remarkably efficient system of social cooperation and elegant bioengineering. They will survive this setback and live to regroup and start another colony, hopefully in a better location. Skeptical ants would do well to stick with the program. 

In a strange and oddly effective experiment, researchers actually flash-froze one of these rafts in liquid nitrogen then hosed the permanently stilled mass of ants with a Superglue wash to hold them steady for closer examination and saw exactly what they had been up to. It turns out they were using jaws and feet to hold on to each other’s legs; one ant may have been in the grasp of up to twenty other surrounding ants. Furthermore, they tended to lay perpendicular to one another other to present the greatest number of grabbing points. With three joints on each of six legs and by holding each other at a relaxed, slightly less than “leg’s length,” they can make a very flexible floating island of cooperative social cohesion allowing the ant mass to mimic the flow of a viscous liquid and spread out like a puddle on the water. 

This technique also creates a bunch of places for air pockets that help hold the whole group afloat. The ants have also been observed taking their plump, buoyant young, the white larvae in the mound that are presumably sealed and tucking them underneath. Additionally, the nature of an ant’s hide or “cuticle” is such that it is naturally water repellant plus they excrete a little oil on themselves for good measure. The rough texture of the cuticle and tiny hairs on its surface help capture and hold a thin layer of air against the ant’s body providing more buoyancy and a life-giving air supply. 

For those of you who hate red ants with a purple passion or if you simply have a mischievous or devious bent, you’ve got ‘em where you want ‘em. You can neutralize all their natural advantages by simply placing a drop or two of dish-washing liquid on them. This acts as a “surfactant” that neutralizes the oil, lessens the water tension, dissipates the air bubbles and lets the viscous South American invader find they are no better than anyone else in this situation and are actually denser than water and are going down.

Last modified on Saturday, 05 September 2015 17:38

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