Though minidragons have 60’ infravision, they are not usually nocturnal. When trying to frighten or warn off a creature, they are capable of emitting a very loud and piercing hiss. Minidragons are also able to spit harmless spittle at an opponent, perhaps for the purpose of frightening it
Racial bonus on Intimidate checks?
Updated.
For corrosive spit, Ex like an ankheg's spit acid ability, or Su like a dragon's breath weapon?
We can probably modify the following to include the symbol of pain effect Cleon described above, and damage to armor...
Spit Acid (Ex): 30-ft. line, once every 6 hours; damage 4d4 acid, Reflex DC 14 half. One such attack depletes the ankheg's acid supply for 6 hours. It cannot spit acid or deal acid damage during this time. The save DC is Constitution-based.
That all sounds reasonable. If we're making it like a breath weapon in frequency, then I suggest Su like dragons' breath weapons.
Seems pretty good to me, although I prefer a Fort save to avoid the excruciating agony. Just seems like a physical effect to me.