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[Zeg]

I've set up a spider slik factory (REGULAR cave spiders, not giant ones, I must point out), basicly consisting of a room where I've released a bunch of cave spiders my trapper had caught. Now, since they are vermin, I tried my best to make this work. The room is dug out in the mountain, with no corridors or other rooms above or below on the adjacent z levels, plus I rewalled and refloored the entire room with constructions. The entry way is a line of 10 adjacent doors, all set to no pet access (not that I had any cats until some stupid migrant brought one along, but I thought it might help).

All seemed well. I let out the 8 spiders I had captured and they went to work building a whole bunch of webs. It only took a couple of months for almost every tile in the room to be covered, which is well over 100 webs, and I harvested a few of them without any problem. However I went back to check if they'd replaced the ones I'd harvested and all of a sudden theres not a spider to be seen.

So... any ideas why? As far as I know, vermin don't need to eat (like all animals) and I would have thought cave spiders would have been quite at home in the mountain. I heard that some vermin hibinate (or vanish at least) over winter, but its mid summer. I'm not sure if vermin have a lifespan, which would make sense as a probable cause of thier sudden vanishing, but would this mean eventually every spider on the map will die, or is there some way they get 'spawned'?



On a different note, if anyone wants it I'll try and see if I can work out how to get the seed out of this map, because I seem to have struck it lucky in this location. I have my embark screen to show magma, but not any other features, but on this map I hit a (fairly tiny) open air chasm AND almost right next to the magma vent I've hit the top of an Adamantine vein. Plus the map biomes have sand, sedimentary layers with magnatite showing, marble and a brook up at the top of the mountain. Its easily the best location I've ever had, so I'm really trying not to screw it up hehe.

EDIT: A file export later and heres the seed.

Spoiler (click to show/hide)

Created in DF v0.28.181.40d.

[WORLD_GEN]
   [TITLE:LARGE]
   [SEED:883996304]
   [HISTORY_SEED:3513537844]
   [NAME_SEED:1923080024]
   [DIM:257:257]
   [END_YEAR:1050]
   [BEAST_END_YEAR:300:80]
   [REVEAL_ALL_HISTORY:1]
   [CULL_HISTORICAL_FIGURES:1]
   [ELEVATION:1:400:800:800]
   [RAINFALL:0:100:400:400]
   [TEMPERATURE:25:75:400:400]
   [DRAINAGE:0:100:400:400]
   [VOLCANISM:0:100:400:400]
   [SAVAGERY:0:100:400:400]
   [ELEVATION_FREQUENCY:1:1:1:1:1:1]
   [RAIN_FREQUENCY:1:1:1:1:1:1]
   [DRAINAGE_FREQUENCY:1:1:1:1:1:1]
   [TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
   [SAVAGERY_FREQUENCY:1:1:1:1:1:1]
   [VOLCANISM_FREQUENCY:1:1:1:1:1:1]
   [GOOD_SQ_COUNTS:100:1000:2000]
   [EVIL_SQ_COUNTS:100:1000:2000]
   [PEAK_NUMBER_MIN:50]
   [OCEAN_EDGE_MIN:2]
   [VOLCANO_MIN:25]
   [REGION_COUNTS:SWAMP:1032:7:6]
   [REGION_COUNTS:DESERT:1032:7:6]
   [REGION_COUNTS:FOREST:4128:13:12]
   [REGION_COUNTS:MOUNTAINS:8256:9:9]
   [REGION_COUNTS:OCEAN:8256:7:6]
   [REGION_COUNTS:GLACIER:0:0:0]
   [REGION_COUNTS:TUNDRA:0:0:0]
   [REGION_COUNTS:GRASSLAND:8256:13:12]
   [REGION_COUNTS:HILLS:8256:13:12]
   [EROSION_CYCLE_COUNT:250]
   [RIVER_MINS:400:400]
   [PERIODICALLY_ERODE_EXTREMES:1]
   [OROGRAPHIC_PRECIPITATION:1]
   [SUBREGION_MAX:2750]
   [CAVE_MIN_SIZE:5]
   [CAVE_MAX_SIZE:25]
   [MOUNTAIN_CAVE_MIN:100]
   [NON_MOUNTAIN_CAVE_MIN:200]
   [ALL_CAVES_VISIBLE:0]
   [SHOW_EMBARK_RIVER:2]
   [SHOW_EMBARK_POOL:2]
   [SHOW_EMBARK_M_POOL:2]
   [SHOW_EMBARK_M_PIPE:2]
   [SHOW_EMBARK_CHASM:2]
   [SHOW_EMBARK_PIT:2]
   [SHOW_EMBARK_OTHER:2]
   [SHOW_EMBARK_TUNNEL:2]
   [TOTAL_CIV_NUMBER:10]
   [TOTAL_CIV_POPULATION:20000]
   [PLAYABLE_CIVILIZATION_REQUIRED:1]
   [ELEVATION_RANGES:8256:16512:8256]
   [RAIN_RANGES:8256:16512:8256]
   [DRAINAGE_RANGES:8256:16512:8256]
   [SAVAGERY_RANGES:8256:16512:8256]
   [VOLCANISM_RANGES:8256:16512:8256]

... and the location. I don't think thats the exact embark area I'm on, but it definatly covers all the features.

Spoiler (click to show/hide)

[Alexor]

I'm not entirely sure about this one, but...do your dwarves have easy access to the spider room?  Dwarves tend to occasionally eat vermin for no reason.

[socially_inept_butterfly]

I can't help you with your problem, but I would like the seed...

[MetBoy]

Personally, I'd carve out the silk farm next to whatever is causing the cave spiders to naturally spawn. Much less trouble in the long run than catching them.

[Zeg]

I'm not entirely sure about this one, but...do your dwarves have easy access to the spider room?  Dwarves tend to occasionally eat vermin for no reason.

Well, most of the time while I wasn't harvesting the webs I kept the doors locked. My dwarfs have been eating some of the other vermin my trapper has been catching, but not quick enough to wipe out all of the spiders even if I had left the doors unlocked I suspect. Plus I think dwarves normally go for vermin still in thier cages rather than trying to chase them around and catch them themselves unless food supplies are very low.

Personally, I'd carve out the silk farm next to whatever is causing the cave spiders to naturally spawn. Much less trouble in the long run than catching them.

Well, yes. But on the other hand, I figured capturing them would also prevent them from escaping again, hopefully giving much higher web production. Which did seem to work somewhat, theres quite a few webs around the natural edges of the chasm, but nothing like as concentrated as my web room.

[Lazer Bomb]

Is it possible the spiders escaped? They can teleport short distances, like most vermin (as far as I know).

[Lightning4]

Were there any cats around? Cats love to kill any vermin around, and your little spiders are the perfect treat for them, sadly.

[Fossaman]

Keep in mind that if you dig out rooms next to the chasm, spiders will actually spawn there. So even if you don't see many webs in the chasm, they'll show up in the farm rooms.

[Dwarfu]

Don't vermin just wink in and out of existence?  Perhaps it was just their turn to go.

Once you discover a chasm, cave spiders will spawn here and there.  But there is a limit as to how far away from the chasm they spawn.  Perhaps your room was too far away and once they winked out of existence they'll never respawn in the room.

Anyways, nice idea to have a little spider farm room.

[Zeg]

Is it possible the spiders escaped? They can teleport short distances, like most vermin (as far as I know).

This is why I hoped building the room seperated away from the rest of the fortress with alot of doors in one corridor would work. Though if they were escaping just by thier movement I would have expected a gradual decline.

Were there any cats around? Cats love to kill any vermin around, and your little spiders are the perfect treat for them, sadly.

Also, hopefully prevented by the door lines. I certainly never noticed the one cat in the fortress going down in that area, or any spider remains the the refuse pile.

Keep in mind that if you dig out rooms next to the chasm, spiders will actually spawn there. So even if you don't see many webs in the chasm, they'll show up in the farm rooms.

This I kinda guessed, but having rooms opening onto the chasm seemed a little insecure to me. Though the thought occurs that maybe you could open a room to the chasm and then rewall it. Depending on how far/through what vermin can teleport in thier movement, the spiders might get behind the wall into your safe room.

Don't vermin just wink in and out of existence?  Perhaps it was just their turn to go.

Once you discover a chasm, cave spiders will spawn here and there.  But there is a limit as to how far away from the chasm they spawn.  Perhaps your room was too far away and once they winked out of existence they'll never respawn in the room.

Anyways, nice idea to have a little spider farm room.

I guess the distance thing may be a possible reason. My web room wasn't exactly miles away from the chasm, but possibly there is some kind of limit.

I've run the map a few more months now and it looks possible that the initial cave spider 'spawn' may be dying off. There seems to be less webs around the outside of the chasm (where it sticks out into open air out the side of the mountain). I think the webs get destroyed by rain, as well as all the traders and immigrants walking over them, but overall I'd say they aren't being remade as fast now.

[Erom]

I had a map once where the (phantom, not cave) spiders would slowly dwindle in population, but they seemed to get refreshed from time to time. Like I would go for a while with less and less web produced, then all of a sudden there would be a large explosion of webs. Possibly happens yearly?

[Overdose]

You don't have to expose the fortress to the chasm, just get damned close to it (my last fort was 2 tiles from the chasm itself, and did a fine job of having silk appear randomly inside it in the rooms closest to the chasm). Also, i'm not entirely sure of it, but i heard if you dig out a fort next to a chasm and reclaim it, there will be tons of the little guys running around in it (along with all the baddies you'll have to clear out).

[Tormy]

Perhaps cats killed your spiders? [vermin]
Don't forget cats are ignoring the "pet blocked" doors. [It's a bug]
..but its also possible that your dwarves ate the spiders. 
I don't think that any vermin just magically disappears [that wouldn't make any sense] , however I've never tried anything like this to be honest.

[Silveron]

Are cave spiders immune to all cave spiderwebs? Ive seen other vermin get caught in the webs and turn into corpses/miasma before. If they are getting caught in each others webs... that would be horribly amusing.

[Zeg]

Perhaps cats killed your spiders? [vermin]
Don't forget cats are ignoring the "pet blocked" doors. [It's a bug]
..but its also possible that your dwarves ate the spiders. 
I don't think that any vermin just magically disappears [that wouldn't make any sense] , however I've never tried anything like this to be honest.

As far as I've seen, the tightly closed door option works fine. On the ocassional times a cat does try to path down through the line of doors, they just run up to the first, fall over and then wander off. Which is just a funny picture in my mind... donk!

Are cave spiders immune to all cave spiderwebs? Ive seen other vermin get caught in the webs and turn into corpses/miasma before. If they are getting caught in each others webs... that would be horribly amusing.

I'm pretty certain they are immune. The room was pretty much full of web long before they vanished.

To be honest, at this point all this speculation is pretty moot. My first 8 spider group made enough silk to last me a long, long time. And since then, my trapper has caught me another 8, of which I've only released the first (thinking they maybe got overcrowded), and he has happily made well over 60 webs alone and is yet to vanish.

So, maybe it isn't infinite silk, but in practical terms it might as well be heh.