"realistic" giant insects in d20 System

[woodelf]

So, here's a question for people: i'd like to make the giant insects in my game more "realistic"--that is, not as they really would be (suffocating and collapsing under their own weight), but as they really are, except scaled up in size. For sake of this discussion, i'll start with ants, since that's what i'm planning on using this weekend.

The most obvious change is strength scores have got to go *way* up, compared to what's in the D20SRD. Depending on whether you scale strength linearly, or with the square of length (the most-realistic, i believe), or with mass (i.e., do the Spiderman thing, where he can lift N*(body weight), where N is a constant based on the regular spider), how much they go up will vary. But it'll be a lot more than the 10Str for a Medium giant ant in the D20SRD.

The one i'm wondering about is insects' ability to take a lot of punishment and keep functioning. Part of this is their simple nervous systems, and not much of a brain. Part of this is simply toughness and resilience, due to their differing construction. The question is, would it be best to model this with more hitpoints? Really high Con? DR? High AC? Fast Healing? Something else?

Any other significant changes i'm forgetting, to make giant insects more like their real counterparts?

 

[Crothian]

For the strength, you might want to just give them the ability to lift way more for their strength. One way to have them take punishment is maybe give them achance to ignore snaeak attacks and criticals.

 

[domino]

Well, if you want realism, giant insects go right out. You can only scale something up so much, before it collaspses under its own weight.

It's called the Square Cube Law. Cubing the size only doubles the strength. So, eventually, the critter will be unable to support itself.

http://harmonies.tzone.org/RPGLex/index.cgi/square_2dcube_20law

 

[demiurge1138]

I remember an article on Monte Cook's website suggesting that in order to make giant vermin more like real insects, they should get fortification to a certain degree (say, a 75% chance to ignore crits and sneak attacks) and tremorsense.

Demiurge out.

 

[boredgremlin]

Hmm ants can lift 100 times thier body wieght. So if you wanted to do it in a simple way you could just guess how much an ant that size is gonna weight and look at the strength chart to see what STR can lift 100 times that amount. Its not perfect but its simple.
To make them tougher, 2 ideas. Give them a D12 HD like dragons. And maybe up thier CON since bugs have a different aneorobic system that allows them to basically go all day and not get tired. Also maybe give them DR/- like a barbarian. That will cover thier toughness pretty well. Lol of course then you have to justify why these giant super ants dont rule the world with all the other races cowering in terror.

 

[DMH]

The question is, would it be best to model this with more hitpoints? Really high Con? DR? High AC? Fast Healing? Something else?

Any other significant changes i'm forgetting, to make giant insects more like their real counterparts?

If you have access to Dragon 174, I really suggest that you read the article on giant insects in it.

The major problem is that your saying insects like most people say humans. Insects have so much diversity in form and function that is is very difficult to come up with some hard and fast rules for them.

Some beetles and roaches should get increased CON and damage and most should get a higher AC or maybe even a low DR. A very few insects should have the ability to bypass hardness of wood and softer metals (including iron). Some insects are resistant to toxins and thus should get a poison resistance score (a number which is subtracted from the ability damage) or poison immunity.

All the insects you are going to use should have one thing- very high spot, listen and search bonuses (+20 or higher). Remember that insects are not visual animals, but use other senses such as chemoreception (smell and taste- blindsense) and vibration (tremorsense). Their faceted eyes allow them to see motion much better than us and should get a bonus to initative.

If you give me some idea of what you are going to be using, I can give you a much better answer. I am studying invertebrate zoology at the moment and have several books on entomology. Or if you want some suggestions beyond the typical giant ant nest and preying mantids, I have a lot.

 

[VirgilCaine]

Pretty nifty thread. Seems like you could really up the CR of most of the vermin, making them pretty dangerous...as opposed to the way they are now.

 

[woodelf]

Well, if you want realism, giant insects go right out. You can only scale something up so much, before it collaspses under its own weight.

It's called the Square Cube Law. Cubing the size only doubles the strength. So, eventually, the critter will be unable to support itself.

http://harmonies.tzone.org/RPGLex/index.cgi/square_2dcube_20law

It's much worse than that. Chitin is much less rigid than bone. So long before an equivalent bone structure would collapse, an insect's skeleton would become too floppy to do it's job. There're also some issues with square-cube and muscle attachment area. Plus, exoskeletons don't leave you any room to put more muscles, even if you want to. Oh, and oxygen at sea-level pressure can only diffuse through about an inch of flesh, so any flesh of an insect that was more than in inch from the air would die. That's why i started out my post with:

...more "realistic"--that is, not as they really would be (suffocating and collapsing under their own weight), but as they really are, except scaled up in size.

And the oxygen problem stops you long before the structural issues do--chitin exoskeletons can, empirically, support crab-sized critters on land. But real-world insects are already at the oxygen limit. Up the %age of oxygen in the air, and you could have larger insects, like we had during the Jurassic and earlier, but that's about it.

 

[Lonely Tylenol]

Part of the reason an ant can lift 50 times its weight is because it doesn't weigh anything, and neither does what it's lifting. There's no reason to believe that a 500 pound ant would be able to lift 25 tons just because an ant that weighs a milligram can lift 50 milligrams of breadcrumb. Really, if you're going for realism in any sense of the word, eliminating the physics in favour of the adage that an ant "can lift 50 times its weight" is not going to improve the situation.

And the oxygen problem stops you long before the structural issues do--chitin exoskeletons can, empirically, support crab-sized critters on land. But real-world insects are already at the oxygen limit. Up the %age of oxygen in the air, and you could have larger insects, like we had during the Jurassic and earlier, but that's about it.

Crabs and other marine arthropods breathe by use of gills and oxygen is carried in a circulatory system, bound to a transport pigment. Insects have a tracheal system that actually brings air to the various parts of their body for oxygen to diffuse to the cells that need it. If a fantasy insect is somehow bestowed with some kind of lung (and a decent oxygen transport system), it could conceivably reach larger sizes on the same concentration of oxygen.

 

[boredgremlin]

Well like i said earlier. Any large colony type insect is going to be stronger, more sensitive and completely fanatical in action. So why arent people being farmed for food by big ants? After all little ants farm aphids. You have to cut them down somewhat from what thier maximum effectiveness could be.