From: "Mark" 

http://blog.foreignpolicy.com/node/769
"The Indian army is fighting an enemy it hasn't faced in nearly half a
century. No, it's not fighting off British colonialists, nor is it a clash
with neighboring Pakistan. It's rats. Millions and millions of rats. You
know...mean, aggressive rodents of unusual size -- the dirty, grey, fuzzy
kind that are led by their long whiskers as they scuttle around making a
"thp-thp-thp" noise. Every 48 years..."

I've heard of the 17-year locusts, but 48-year rats? 

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