If Arthropods are to get bigger. What kind of changes do their bodies have to make?

Answer 1

The air-tube-system, which lets arthropods breathe couldn't support a very large animal. Terrestrial arthropods would have to develop some kind of lungs and i guess a better vascular system to support the metabolism correctly. The exoskeleton also limits the growth of an arthropod.

In an article i once read, somebody calculated if arthropods the size in "Starship Troopers" would be possible. Apparently it is not, as the exoskeleton couldn't support such a large structure.

I presume that aquatic arthropods could get bigger than terrestrials, because the water would alleviate the weight of the exoskeleton. You coul check on the internet for Trilobita, an extinct animal class of arthropoda. Some of them got really big. Up to about 70 cm if i remember correctly. And in the mesozoic some Odonata got really big too (wing spans up to about 70 cm). I guess this would be about the upper limit for arthropods.

check the sources to find the biggest arthropods i know of.

Answer 2

I think about thermal regulation, a better protection against micro agents (acars, bacteria, muld), for they should need a good gland system in order to provide the necessary secretion.
As a matter of fact, their rigid envelope limits their accretion.
By the way, during the Paleozoic era, some species perhaps had the advantage of a much hotter climate than nowadays and were very big.

Answer 3

Arthropods have external skeletons, and no lungs, so they breathe through gills or air passages. What problems could they cause?

Answer 4

According to the movie Mimic, they need lungs.

Answer 5

masjor ones in the exoskeleton