Getting severe drops in TPS as reported by Spark: https://spark.lucko.me/MPJkNwUnVE

net.minecraft.world.server.ServerWorld$$Lambda$25954/1419910971.accept()84.04%
net.minecraft.world.server.ServerWorld.updateEntity()84.04%
com.github.alexthe666.alexsmobs.entity.EntityLeafcutterAnt.tick()79.05%
net.minecraft.entity.MobEntity.tick()78.39%
net.minecraft.entity.LivingEntity.tick()78.38%
net.minecraft.entity.passive.AnimalEntity.livingTick()68.42%
net.minecraft.entity.AgeableEntity.livingTick()68.42%
net.minecraft.entity.MobEntity.livingTick()68.32%
net.minecraft.entity.LivingEntity.livingTick()68.32%
net.minecraft.entity.LivingEntity.collideWithNearbyEntities()30.12%
net.minecraft.entity.LivingEntity.travel()27.38%
net.minecraft.entity.LivingEntity.func_233633_a_()26.35%
net.minecraft.entity.Entity.move()26.22%14068ms (self: 152ms - 0.28%)

I removed Alexsmobs from mods and TPS is normal.

I had this issue, and used /kill @e[type=alexsmobs:leafcutter_ant] which killed 1517 entities, and my server's TPS recovered from 10 back to 20. I assume they multiply... perhaps that should be capped!