We have really huge birds, mammals, fish, reptiles, etc.
Why do bugs stay so comparatively small? Why don't we see cockroaches the size of rats in cities?

I'm no expert, but I think it has to do with having an exoskeleton, a rat-sized roach would not be able to support it's own weight on such skinny legs.

There are some awfully damn big crabs in Northern waters. Their exoskeleton doesn't seem to keep them small. Why nothave spiders that size running around NY?

holes they take in air through are maxed out for amnt of oxygen the air

back in the dinosaur age the oxygen content was higher and big ass insects did roam

But crabs legs are much thicker in proportion to their bodies....as bugs got bigger, the weight of their body would increase more than the thickness of their legs. ..I could be totally wrong, though

Search & Destroy is probably right, although its not known for certain.

so is there anywhere on earth where oxygen is more? I would think deserts (fewer plants) would have less, but what about the Amazon, with lots of plants. are bugs bigger there?

Some are, I think. Beetles, some spiders, ants. Good point.

Heres an interesting article about Giant Dragonflies (http://www.nytimes.com/2004/02/03/science/03INSE.html?ei=5007&en=f2aca49271f3a30b&ex=1391144400&adxnnl=1&partner=USERLAND&adxnnlx=1122496279-DveBWDIN6jk5jTMJyaRFTA), they had a 30 inch wingspan !

If you scale up a bug's architecture, you get an animal that can't walk or breathe in just a few pounds.

Radical changes in architecture make a different animal. We don't call turtles "bugs".

We have really huge birds, mammals, fish, reptiles, etc.
Why do bugs stay so comparatively small? Why don't we see cockroaches the size of rats in cities?
Oxygen levels are too low these days. In the Carboniferous era, it was different. In that age, there were roaches the size of dogs and dragonflies the size of hawks. Things like that were common, but the oxygen levels in the atmosphere shifted radically in the late Cretaceous.
It's the same reason there aren't 20ft-wingspan birds anymore- not enough oxygen in the air for them to breathe in, to support that massive metabolic rate. They just can't, and their bodies evolved to become smaller.

have humans become smaller for the same reason? If more oxygen was in teh air would we get bigger?

We came around after the major oxygen level shift. But if things keep going how they're going, we will adapt and become smaller. Oxygen levels are going down, partially due to pollutants, but mainly as part of the natural process.

If there were more oxygen, we probably would adapt and have larger bodies. We would be able to support a much faster metabolism, to say the least.

.... But if things keep going how they're going, we will adapt and become smaller. ....

so bugs are becoming smaller?

I don't know. I really can't say for certain. I'm not an entomologist.

I'm no expert, but I think it has to do with having an exoskeleton, a rat-sized roach would not be able to support it's own weight on such skinny legs.Right about the exoskeleton but wrong about the details. A dog-sized roach would need such a thick exoskeleton around its thorax that it would be too ponderous. The legs would probably more easily grow thick enough to encompass the required muscles. (Sorry to be the one to have to tell you this but there actually are rat-sized roaches. Sleep well tonight. :))There are some awfully damn big crabs in Northern waters. Their exoskeleton doesn't seem to keep them small. Why not have spiders that size running around NY?We're talking about the phylum of arthropods and there are five classes within it. Insects, arachnids, centipedes and millipedes are all land-dwelling air-breathers. Crustaceans are aquatic gill-breathers (or something functionally equivalent to gills in the lower animals). Water is a completely different environment that puts different pressures on evolution. Buoyancy makes a phenomenal difference in the ability of an animal's infrastructure to support its mass. The largest animal that ever existed is an aquatic mammal: the blue whale. It makes the dinosaurs look like kitty cats.If there were more oxygen, we probably would adapt and have larger bodies. We would be able to support a much faster metabolism, to say the least.Our evolution is no longer quite so determined by natural selection. As someone pointed out in another thread, we'll probably stop seeing skin color change over the centuries as populations move north or south. Black people can buy vitamin pills to compensate for the vitamins their melanin-rich skin doesn't produce in low sunlight, and white people can buy sunblock to compensate for the lack of melanin to shield them from sunburn in the tropics.

So whatever disadvantage there would be to having smaller bodies and slower metabolism in a higher-oxygen atmosphere would have to be one that we ourselves found to be a problem and could not conquer with technology. Otherwise we'd just give the smaller people the necessary medicine and let them keep on reproducing.

We are the species who lovingly and enthusiastically keep Stephen Hawking alive, after all. :)

(Sorry to be the one to have to tell you this but there actually are rat-sized roaches. Sleep well tonight. :))
Damn, that's not a roach, it's a grenade...

the giant burrowing cockroach or rhinoceros cockroach that is native to Australia, and found in the warm, northeastern state of Queensland.
http://img504.imageshack.us/img504/2492/macropanesthiarhinocerooo6.jpg

We have really huge birds, mammals, fish, reptiles, etc.
Why do bugs stay so comparatively small? Why don't we see cockroaches the size of rats in cities?


Why do humans stay so uneducated?