Ticks are a common North American blood sucking parasite (no, we're not talking politicians here, it's an insect). Most ticks hang out in trees and bushes and drop down on passing animals to burrow in, usually behind the neck if possible, to be hardest to reach. Ticks are disgusting little creatures, tiny when hungry, but as they gorge on their victim's blood, they swell up dramatically, often reaching a centimeter in length. Persistent, too--they don't let go willingly, and pulling off a tick usually leaves the head behind, burrowed under the flesh, where it festers and causes a nasty infection. The traditional way to remove a tick is to "encourage" it by burning its little butt with a lit cigarette to make it back out. Unfortunately, with the decline in smoking, fewer people have the emergency tools handy to remove a tick safely, and so tick-borne infections are on the rise, notably Lyme's Disease.

The rare uptick species has developed prodigious jumping abilities, and lurks at ground level. When an animal walks over it and blots out the light, that's the signal for the uptick to (literally) leap into action, springing up to latch on to the beast's belly. This may account for the rarity of the species, since many animals can easily reach their bellies and bite the tick--that's the downside for the uptick. But many can't, and so the uptick species (literally) clings to survival.

Some people distinguish the two varieties by referring to the common tick as the "downtick", which cleans to the animal's upside; while the uptick clings to the downside. This is why ticks have entered the economic lexicon as metaphors for economic cycles. But, unkown to many people, the terms come from entomologists and not from economists. The fact that ticks are bloodsuckers is coincidental and is in no way a commentary on capitalism.