Another high-powered demon! This one's got 18 RHD, and Huge size.
Stats are the in the +10-20 range like you'd expect, with the exception of a low (ish) +4 dexterity. Natural weapons are an impressive array of a bite, a tail (which drains 1d6 charisma), and six tentacles (with improved grab and constrict), in addition to two pairs of normal arms. Defensive traits include the general demon immunities, DR 15/good AND iron, and SR 30.
The more interesting abilities are offensively-oriented. Myrmixicuses (myrmixici?) have breath weapons that nauseate for multiple rounds upon a failed reflex save. It's not a poison or disease effect either, so it should in theory even work on things like undead and constructs. Good-aligned creatures take unholy damage as well, but let's be honest, you're here for the nausea. The ability is 1/minute, so it'll be usable roughly once per fight.
The breath weapon's effect is re-used for Unholy Ichor, which splatters melee attackers (except for those with manufactured bludgeoning weapons) with blood that induces more rounds of nausea if it's not dodged.
Infuse Scythe is a flavorful ability that turns up to four masterwork scythes touched by the demon into +3 Unholy weapons until they leave its grasp. It may not see much use in the average game, but it sure is flavorful!
Finally, the more overtly magical abilities. Summon Tanar'ri allows the myrmixicus to summon either some skulvyns (CR 4 demons from this book), or a hezrou, both with a 55% chance of success.
The SLAs are an interesting bunch. Most notable are at-will Charm Monster, Freedom of Movement, self-only Greater Teleport, and True Seeing, as well as 3/day Control Weather. While they're a potent array of buffs both for you and allies, they fail to provide much offensive presence.
For now, I'll assign a rather modest +1 LA, but I'm tending towards +2. Do discuss!