Epic crab fight — Watch fiddler crabs duel, big claw-to-big claw

Male fiddler crabs are famous for their mismatched front claws — one great big and threatening, one eensy-weensy. (I used to use this as a metaphor for the split in my SAT scores.) But what's really interesting about this lopsided look is that it seems to serve multiple purposes. The big claw can be used to attract lady crabs — wave it around and it becomes the crabby equivalent of, "Yo! Adrian!" But the big claw can also be used as a practical weapon, where two male crabs go at each other like fancy fencers with one arm behind their backs.

And the extent to which the big claw is for looks or for violence seems to vary a lot depending on the species of fiddler crab, writes scientist John Christy. Some have a lightweight claw that's better for waving at the girls, but weaksauce in a fight. Others have a heavy, dangerous claw that's difficult to use for long-distance flirting. Christy and his team are in the process of trying to figure out what selection forces leave some crabs optimized for love and others for the battlefield. In the meantime, though, they made this awesome crab fight video, set to a stirring, John Williams-esque soundtrack.

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"Riot" at kindergarten graduation

A brawl erupted at a kindergarten graduation in Cleveland on Friday, leading to eight arrests. It seems that two teens started the fisticuffs, and then some adults joined the fray. According to the Cleveland Plain Dealer, "eventual charges could include aggravated rioting." None of the graduates were taken into custody.

Ant wars: Battle of the invasive species

There's a war on in America, pitting invasive ant against invasive ant in a fight to the finish. It's sort of like Alien vs. Predator, in a way, because whoever wins ... we lose. Argentine ants (the reigning champions) have wiped out native ant species in many of the environments they've invaded over the years, affecting the survival of other animals that used to feed on those ants. Worse, they have a fondness for certain agricultural pests, like aphids. In places with lots of Argentine ants, aphids do very well — and plants do worse.

But now the Argentines are facing a serious challenge in the form of Asian needle ants, another invasive species that — for reasons nobody really understands — have suddenly gone from minor player to major threat in the last decade. The big downside to Asian needle ants: They sting. They sting us. And, right now, it looks like they're winning.

John Roach tells the story at NBC News. But you can get a good idea of what this matchup looks like by checking out the work of insect photographer Alex Wild. That's his picture above, showing an Argentine ant on the left and an Asian needle ant on the right.