Trees, rocks, and a couple other things have a chance to spawn biters when a they are destroyed. It is fully customisable with all fetures being enabled or disabled independently. This mod is inspired by but not derived from https://mods.factorio.com/mod/i-speak-for-the-trees.

With this mod you can spawn a number of biters after a tree dies, a rock dies, a spawner dies, or after part of your base dies (the last is disabled by default). It will chose a biter or spitter apropreate for the current evolution to a max evolution (0.9 by default).

--Settings--

• Max Evolution - highest evolution biters that will be spawned, if the evolution goes above this value this mod will use the evo in this setting instead. range 0-1, default 0.9

• Biter spawn chance - Chance that a biter will be chosen from the biter spawner instead of a spiter spawner (0.6) ex: 0.6 means a 60% of chosing something a biter spawner could spawn at the current evolution, 40% of chosing something a spitter spawner could spawn. range 0-1, default 0.6

• X revival chance - Percent chance that when X dies or is mined it will spawn any biters. 0 to disable biter spawning for X

• X revival number of biters - Number of biters that spawn when X spawns biters.
• Apocalypse include mining - whether to trigger apocalypse spawning if you mine a building (if false it triggers only on building death, if true it triggers on both mining and death). options: (true, false), default: false

--Items for X--

• tree - any tree, including modded trees. (anything of type tree)
• rock - any rock, including modded rocks. (anything with the tag count_as_rock_for_filtered_deconstruction, this tag controls if an entity is selected by a decon planner with Trees/rocks only)
• Spawner - any biter/ spitter spawner, including modded spawners. (anything of type unit-spawner) Does not include worms.
• Apocalypse - Any players buildings that are not walls or gates... including gun turrets. Your defenses will need a boost. The 'Apocalypse include mining' setting controls if apocalypse affects mining building in addition to killing them too.

--Preset information/suggestions--

the primary ways to set the settings for each type of biter spawning are

• frequent but small- higher chance to trigger (10-40%) but small attack groups (1-5 biters) - constantly makes things a little more costly but not very dangerous
• rare but dangerous- low chance (0.2-1%) but large attack group (20-100 biters) - usually doesn't happen but when it does it is quite bad.
• frequent and dangerous- higher chance to trigger (40-100%) and large attack group (20-100 biters) - you just don't do this thing now. Just put an underground under the rock, it is easier. Biter bases with this setting require overwhelming force to assault. Trees with this setting is a bad idea for UPS reasons.

The above percentages are for trees, they should be increased for rocks or spawners and decreased for apocalypse.