I really like starcraft, and i say this ability fits well to the zergs' parasitic style.
If you don't have SC i recommend to buy it (it's not that expensive) and it's a very great game.
Now about this map.
The idea is excellent, except the baby zerglings spawning into adult ones doesn't worked for me either, so i took a look at ur triggers.
I think these spells could have been made much-much easier:
The zerg lord summons four zerglings. There's no problem. The zerglings eat out a unit:
here comes a trigger:
Events: a (generic) unit dies
Conditions: killing unit = zergling
unit type not=zerg egg and zerg baby
Actions:
-create 1 invisible egg caster (this unit would have an ability to cast a Sentry Ward what summons an egg instead, what lasts around 15-20 seconds)at position of dying unit facing position of dying unit
-order last created unit to place Sentry Ward at position of dying unit
-w8 1 seconds
-pick every unit by type(unit type=invisible caster) and remove picked unit (this can cause bugs but in really rare cases)
Trigger to spawn baby lings:
Events: unit dies
Conditions: dying unit = zerg egg
killing unit = no unit
Actions: another action like the one before: 1 invisible caster2 what summons a zergling baby with 10-20 second timer, then removes the inv. casters
Trigger to turn into adult ones:
a trigger like before summons a third type of invis. caster what summons an adult zling with a longer timer.
No variables were used, and much shorter triggers, and no periodic ones
There's an even easier method what doesn't even use triggers: (but i'm not sure it'll be perfect)
zerglings has black arrow ability, what has 0 second duration and spawns zerg eggs with a timer.
zerg eggs has spawn spiederling ability (u know what the nerubians have - they spawn little spieders on death) what spawns baby lings on death with a timer (i'm not sure this works on death cases caused by timer..)
baby zerglings has also spawn spiederling ability what spawns timed adult lings.
If you find erroes in these methods it is probably because i was improvising, and i didn't test this in WE...
And a few tips:
remove space felorcs... (if i try to help out the lings, they kill the units before the lings can do)
separate creeps to make easier to kill them with just zerglings
remove that annying lag-factory outland wind weather effect....
I give you a 5 because you wrote trigger what i don't even understand

and i'm sure you'll be able to fix the baby ling spawning into adult problem (or tell us whad did we wrong)