We're definitely working in the dark, but i don't see any compelling reason to suggest that ants aren't self-aware; why wouldn't they be? What about their behavior makes you feel like they aren't?
The compelling reason for me is the mirror test, and what you can infer from it. The tiniest bit of self-awareness lets you pass the mirror test, as toddlers demonstrate. Apes pass, elephants pass, and magpies pass. Monkeys fail. What's different about monkeys? They have smaller, simpler brains. If a monkey by all appearances has no concept of self, an ant with 0.008% as many neurons assuredly doesn't.
(Philosophers are definitely not self-abnegating. They are on a career track. Soldier do exhibit self-sacrifice, but quite a lot are conscripted against their will, and require a bit of re-education in boot-camp.)
Humans are capable of self sacrifice for a cause. Duty, honor, love of one's homeland, spiritual convictions, etc.
These are psychological motives and forces and their factual impact on the subject person is observable.
I just recently saw Eien no Zero (aka The Eternal Zero). If that movie reflects the actual events, then the pilots were subject to serious psychological stress coming to terms with their duty to Japan.
If we can ever measure 'psychological stress' in ants, then we can observe if they experience a shift from a normal psychological state to a stressful one before "deciding" to sacrifice themselves on whatever heroic ant task awaits them.
