Should this say "to target creature with flying"?

Nope, Screeching Spider can hit any target, its sound waves ;D

You should know that's very outside the modern colour pie, then.

How so?

In the modern color pie, green does not do pinging effects. If you want green to deal damage to a creature, either that damage should be limited to creatures with flying, or the damage should be dealt in the form of a fight. Completely unrestricted pinging is red.
Green also doesn't really tap things, to my knowledge. That ability is white.
This ability appears Stun Sniper, a card which is red and white.

It should be pointed out that, while I agree with Alex and Link, things do get very weird in the color pie for green sometimes... especially around hornets and wasps for some reason. See also Unyaro Bees, Giant Dustwasp, Hornet Sting, Hornet Queen and... um... Beast Within (which I personally think is too far out of color pie, but everyone else seems to enjoy, so what do I know?)

So, yes, green sometimes uses flavor to exhibit non-standard color pie traits. But it usually does it by looking at an animal that would be green (Hornets) and pointing to the thing that that animal does that isn't very green (deal damage to people and fly). Screaching Spiders (as awesome as that idea is) don't exist in nature, so the color pie stretch is harder to justify. Especially when, flavor aside, the creature could just be red/white or red/green (blue/red? white/black?)

That said, I do like the creature. I'd give it a pass as just an oddball. I'm sure others wouldn't agree with me.

Green gets the sniper ability; but yeah, only against flyers - Matsu-Tribe Sniper.

This calls out to that, with reach; so that's how I'd change it to fit. But it's a huge cost, so I might give it a pass as just "Ok, green pays through the nose to get it"

jmpariepy, you mention that "screeching spiders" don't exist in nature" and I'd like to address that:

1. MTG is definitively not "nature" as we know it. and 2. we have not discovered every spider species on the planet, nor researched all the ones we have to find out if, or if not a "screeching" spider (or ultra-low/high frequency sound manipulation) exists or not in nature as we know it. We know other animals are capable of the feat in a variety of forms, but with so many undiscovered and under-studied arachnids, we might not know for ...ever.

@Joz: That's fair. But I'm not really talking about possibilites so much as player expectations. Players seem to be okay with things they recognize in the real world taking on fantastic proportions in the Magic world, and being allowed to break the color pie because of it. I don't know why, exactly. I could speculate, but I assume I'd be here for another 5 paragraphs talking out my bum.

Show a player a perfectly reasonable animal that doesn't exist, as far as they know, and stretch the color pie, and all of the sudden that can't be done. I suspect it has something to do with the fact that, instead of a screaching spider, you could have made a screaching lizard that's red. You're not forced to stay in green; you're choosing to stay in green, and that makes some players buggy.

As for animals that attack by tossing sound like a cannon: I'd be surprised if there wasn't an animal that didn't do that. I know that there are fish that stun other fish by lighting up like a thermal grenades in the darkest parts of the ocean. Using sound to induce a similar effect doesn't seem that far off.

I'm not disagreeing with the fact that some people might disagree with a green card that deals damage to creatures unconditionally. But the simple fact is, is that dealing damage in this way isn't so far out of green anymore. Taking a look at green cards that deal damage or an effect of such:

Arashi, the Sky Asunder, Choking Vines, Durkwood Tracker, Garruk Relentless, Greatbow Doyen, Hornet Sting and others. the Screeching Spider design isn't so out of color or flavor at all for green as long as it is implemented correctly - which I do believe I have done.

­Arashi: flying only. Choking Vines: too old. Durkwood Tracker: fights. Garruk Relentless: "fights". Greatbow Doyen: combat based. Hornet Sting: a mistake. None if your examples are valid. Flavor is not an acceptable excuse to stretch the color pie.

Man, what an old argument this is. I'm sure they were debating this problem in 1993 as well, and I'm pretty sure they'll be arguing about it in 2033. Classic Vorthos vs. Melvin. Most of the time, in WotC, it seems like Melvin wins the argument... but then a card like Horent Sting gets printed, Vorthos gets a win, Melvin doesn't count the ocaasional win, calling it a 'mistake', and the argument begins again.

Here's the good news: It's a healthy argument. I don't think Magic should ever have flavor trump mechanics, or mechanics trump flavor. I also think it's important for both sides to win on occasion. That taps me as far as advice goes, though. I'm pretty sure this isn't an argument that you can 'win'. ­

Ok, I fixed the card - by adding flavor text.

For the record, I'm more a Vorthos than a Melvin, but I think that internally consistency trumps both. Also, I'm not calling Hornet Sting a mistake; Mark Rosewater, Head Designer is.

One of the worst things about Hornet Sting is that it will be perpetually cited as an example by amateur designers.

In case you don't know: Mark Rosewater is of the opinion that Hornet Sting is a great mistake. He wasn't the designer of the Core Set where that was printed, though, and he got outvoted by that design team. (ref) (further reading)

Flavour text doesn't excuse out-of-pie mechanics. But you could happily make a green card with the "soundwaves" flavour if it fights the creature and also taps it down. (Perhaps the flavour is that when something gets hit by the terrifying screech, it comes and punches the irritating screeching thing.)

Hmm, fighting,I'll try that out.

This is a strong fighter - definitely not common, probably rare.

I felt it was balanced at 2CCC. Maybe needs to be a 3/4?

Fight with things that are smaller than a specific power or toughness?