But about a year ago I conceived of the tables which will follow, which represent only a small fraction of the whole ... but if I am going to wait until I have all of them, I'll be posting this sometime between 2014 and 2018. Damn, I hope it doesn't take that long.
The tables are still based on a grouping principal, but one of behavior rather than biology. They are presented here in the hopes that they will be helpful. For the most part the intelligence, number appearing and dimensions correspond to the books - but not always. I felt free to redefine something's intelligence or other characteristic as it fit my purposes, or as it seemed to more logically fit into the whole.
Diving straight into it, I'll write notes as we go along. The first set of behavioral groups all have zero intelligence.
'Density' would be a description of what pattern of inhabitation the creature has in a hex. In this case, 'scattered' would mean that it would be unlikely to find more than one floating eye at a time. The number appearing, as I've chosen to interpret it, would not be the number of eyes per encounter, but per hex - per incidence of that particular monster being rolled. In other words, if you were to say that there were 30 types of monsters in a hex, and you rolled 30 times, each time you rolled up 'eye, floating' there would be 1-12 creatures in the hex.
The contact distance is a calculation based upon the number of creatures and the size of the creature. Because floating eyes are so small, any distance greater than one hex (a distance of 5 feet) would be extraordinarily unlikely - particularly since they are only encountered under water.
While the 'encounter' column should be self explanatory, the 'gestation and growth' column will probably need a lot of notes. In this case, the floating eye leaves an eggsack full of its young in an area of low shallows ... which itself could be found independently of the creature itself. It could also be disturbed, causing many, many tiny floating eyes to emerge all at once - perhaps as many as 4-10 times the number normally appearing. Remember that most young floating eyes would be eaten before reaching full growth. but four dozen little ones (with a bonus to saving throw, perhaps, and each with 1 hp) would be an interesting disaster.
The list gives a wide arrange of dimensions for various creatures that, in the real world, would collapse under their own weight: the 41 lb. fire beetle, for instance. All weights were calculated exponentially from existing creatures, to the best of my ability. Some creatures, such as the shark, actually are as large as indicated ... remembering that in all cases the maximum dimension is given. Thus, a shark could easily be much smaller than 2 tons ... but as the shark in the monster manual has 3 to 8 hit dice, the gentle reader may assume that the largest dimension refers to 8 hit dice. (the giant shark, incidentally, has a higher intelligence and thus fits into a different behavioral category).
Note that in this case every creature's purpose in life (on this table) is to feed, and nothing else.
The progressive attack would mean that, once the melee was started, every set number of rounds another creature would join, then another, then another and so on, until the entire number is involved. A 'swarm' means that every creature attacks at once, and at the same time. A milling approach would mean that the creatures would move about the party without attacking for potentially forever, until provoked - like being in the room with a bee, which is aggressive but yet roams around before having a reason to sting.
Creatures may also be movement sensitive, and will strike from cover (such as the weed eel), or by simply moving at the party in a direct attack (the ochre jelly).
There are a number of eggsack types, pushed into mud, a dead carcass, or carried along with the body. Ochre jellies obviously just split in two (fission) ... while manta rays produce live births from eggs they carry in their own bodies.
Swift growth or swift molting would mean the creature grows to full size within a season after birth, sometimes faster.
The only treasure here are the natural light glands that the fire beetles carry as part of their bodies.
(I note there is one forgotten note - a fire beetle can be seen at twice the contact distance if it is dark).
The 'fuzz stage' described under gestation refers to a point when the plant splits and releases great quantities of seeds into the environment, much like a cat-tail. I once wrote about this when I redesigned my gas spore. A detailed description of the yellow musk creeper (using zombies to spread its growth) is given in the Fiend Folio.
Those collecting food will hunt over a wide area, and may be encountered outside the lair. They will not eat their victims, but will typically paralyze them or render them otherwise harmless, and carry them back to the lair. Durables would then be found in the lair since the carried body is not stripped of its equipment before being carried away.
Not every creature is inherently violent. The dragonfish is bothering no one when it is stepped upon and thus releases its poison; a stinkbug reacts equally defensively (whereas the bombadier beetle in the former table is aggressively meat-eating, the stinkbug is herbivorous). The giant sea turtle is not destructive - it does make a great friend, however, if speak with animals is employed.
A very large section. A great many monsters are designed to be party killers - that would be the primary reason for most of these. A number of these attack by surprise, from beneath the water, by dropping from trees, from rock crevices or even from inside solid rock (thoqqua). Beyond that, the table largely speaks for itself.