Why Leafcutter Ants are Interesting

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An Acromyrmex ant trundles along merrily with its gargantuan load. (c) Alex Wild

• Leafcutter ants are the only animals (besides humans) that take fresh plant matter and grow their own food from it.
  
  
• Leafcutter ants use antibiotics from strains of bacteria to combat alien fungi that invade their "farms". The Streptomyces strains are found in specific body parts of the ants and are transmitted vertically across ant generations by the queens! Interestingly, the leafcutter ants have been able to ward off fairly successfully the invasions of pests for millions of years using these techniques, whereas we humans have only been doing it for a few decades, and already many of our bacterial foes have developed strong resistance against our array of antibiotics. Could we learn something from the ant?
  
  
• Leafcutter ants are THE dominant herbivores in the neotropics, with the amount of vegetable matter being cut estimated at an astonishing 12-17% of annual leaf production. Damage (indirect and direct) has been estimated to be in the billions (USA dollars) annually. The grass cutting species reduce the carrying capacity of pasturelands in the area by as much as 10%!
  
  
• Leafcutter ants utilize advanced waste management systems that prevent the spread of disease and pathogens in their vast underground cities. Waste (including exhausted and diseased fungi, dead ants, etc) is excluded from the colony proper by behavioral and architectural innovations. For example, there are specialized "heap workers" who spend their entire time in the huge waste heaps, turning over and aerating the garbage piles in order to hasten decomposition.
  
  
• Atta large nests are architectural ant marvels, with some nests descending 6 meters deep, and with air circulation being controlled by the movement of warm air, flowing into the outer perimeter nest holes and out through the center holes.
  
  
• The Atta have the largest size differential in workers right after the Pheidologeton. According to 'The Ants'..the head width varies 8-fold from smallest to largest, and the dry weight varies 200-fold...
  
  
• The estimated populations for mature Atta colonies number in the millions (up to 8 million in some estimates)!
  
  
• The large soldiers are so tough they can cut through leather!
  
  
• Their colonies are models of efficiency, with the highly polymorphic wokers each optimized for particular sets of tasks..at the smallest end you have the tiny workers who tend to the fungi and feed the rest; graded in the lower end are the workers that can perch on carried leaves and defend their sisters from marauding flies; in the middle to large range are workers who are optimized for cutting leaves and twigs; and in the largest sized workers we find individuals who specialize in defending the colony against large invertebrates and vertebrates.

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