The insects would have to act in coordination to take down our sophisticated transportation and communications networks, to keep us dumb and immobile until it was too late. To attribute such a level of coordination to them, I submit, gives them intelligence and communication powers far beyond our own.

If they played dumb and acted as they usually do, they could wait until they solve these problems before striking. I’m not confident that they’d be completely solved–there’d always be some fuckup ants who forgot to chew through the translantic cable, or some charismatic bee who is sick and tired of listening to the head bee drone on and on and spies for the humans, or something. But that assumes that they could play dumb in the first place–what happens when they first become sentient? They don’t have any communication networks set up, they’re scattered around the world, they have no leaders. They’d divide into factions and have their own squabbles, just like humans and every other animal. The takeaway: the level of coordination required is implausible.

I like the birds of prey pick.

Who’s to say that a hyperintelligent cockroach wouldn’t still prefer to rut all day in a bin of mouldering apples? He’s got no worries in life and lots of cockroach pleasures.

Piranha, on the other hand, are scary enough without the ability to scheme.

all super intelligent ants would need to do would be to figure out a way to burrow about 50 of them into our brains or around our hearts - those who do what they say, will just be carrying some hitchhikers around - those who don’t, get holes bitten in their brains or hearts and die

it would be even simpler for super intelligent bees - they could genetically engineer themselves to sting with cobra venom - and then there would always be a few hovering over us, making sure we did their bidding or else - in time, they could even selectively breed us to become more docile and obedient

so my vote’s for bees

Now here’s the big scary thing: what happens when the bees, hornets, wasps, ants, spiders cockroaches and related insects all gain intelligence? Will they plot together against the huge human infestation or fight amongst themselves for supremacy?

And there’s one important thing to remember. With advanced intelligence comes self-awareness. And the instinct of self-preservation. Are thirty-thousand ants really going to try and push me out the window knowing there’s an excellent chance I’ll stomp most of them into the carpet before they even get close enough? Making the case for hyper-intelligent insect who are also religious fundamentalists is just too far of a stretch.

Plus there’s the point cortex Josh brought up: brain size. Could an insect ever conceivably house enough neural pathways to attain intelligence?

The answer is going to be a bird: eagle, hawk, buzzard, egret. A lot of these are endangered, so my pick is going to be the biggest bird of prey with the largest total population (I have no idea what that is). Most birds are very dexterous with their beaks and talons—no thumb required. Take their nest-building, for example, or the burglarizing/stockpiling antics of magpies. The advantage that intelligence gives us is tool-building and usage. Physically, we’re in no position to be Earth’s kings. So, given their inherent dexterity and new-found intelligence, I’d say it’s only a matter of time before intelligent birds start designing weapons. I’d imagine some sort of slingshot they grip with both talons and pull back on the ammunition with their beaks. Or they can scavenge for the parts for pipe bombs. In the short term, they can steal existing weapons like grenades as Marie Mon Dieu postulated. They’re small, fast, have great eyesight, are already equipped for communication, and can escape to places we cannot follow. Depending on their beginning population, I’d give us 5-20 years until extinction.

That or bears. They are fucking huge.

Are we counting viruses as living organisms? Bacteria?

Some loose alliances, sure. Probably some major predator groups would organize to try to avoid a competitive slaughter that’d destroy the food supply; likewise prey collectives trying to keep things in check and back each other’s defenses. But when push comes to shove, they’re all a bunch of animals.

In the end, the ants are only held in check by the bees, who have used their own Over-mind for good, rather than evil, and have worked with rebel male ants to infiltrate the drone ranks and overthrow the Queen. Using their wings and stingers, they successfully manage to stop the March Of The Ants.

In the new world order, the world will be divided in half, the product of an uneasy truce between the Ants and the Bees. Remaining humans will be nonexistent in the Ant empire, but will enjoy moderately pleasant lives in the Bee empire, where 99.9% of the human population will be devoted to horticulturalism.

Bees could probably take out quite a few humans until we could organize some kind of insecticide counter-attack. Assuming a roving drove of bees could sweep human civilization going on a sting-kill spree, I bet they could take out half the population. If they figure out how to use door knobs.

Why would they even deign to acquire lower intelligence such as ours? (And they did all this without thumbs, because, hey - if your slaves have thumbs, why do you need ‘em?)

Wake up, pod people, and observe the Felinarchy! You are mere constructs in Fluffyland.