What is the thesis to "The Battle of the Ants"?
Likening the red ants and the black ants to "the republicans (colonists) and the imperalists (the British)," Walden compares the battling insects to humans:
For numbers and for carnage it was an Austerlitz or Dresden. Concord Fight! Two killed on the patriots' side, and Luther Blanchard wounded! Why here every ant was a Buttrick--"Fire! for God's sake fire!"--and thousands shared the fate of Davis and Hosmer (two colonists killed)....I have no doubt that it was a principle they fought for, as much as our ancestors, and not to avoid a three-penny tax on their tea; and the results of this battle will be as important and memorable to those whom it concerns as those of the Battle of Bunker Hill, at least.
Clearly, Thoreau satires the importance that men have put upon going to war on "principle." Facetiously, he earlier compares the red ant who runs into battle to the the Spartan whose mother told their sons to return victorious or dead: "It was evident that their battle cry was "Conquer or die."
Studying the red and black ants fighting for no other reason that they hate each other, or one has taxed the other, brings Walden's passage to the point/thesis of the futility of war as well as the terrible waste of life that it is.
I never learned which party was victorious, nor the cause of the war; but I felt for the rest of that day as if I had had my feelings excited and harrowed by witnessing the struglle, the ferocity and carnage, of a human battle before my door....
WASTE OF LIFE:
Whether he finally survived that combat and spent the remainder of his days in some Hotel des Invalides (a veteran's hospital where the injured of the long Napoleonic Wars were sent). I do not know; but I thought that his industry would not be worth much thereafter.
I believe that what Thoreau is trying to say to us in this story is that human battles are ultimately pointless. I think he is trying to argue that our battles are no different than those of the ants.
I think you should look at how closely Thoreau details the fighting that happens between the ants. He makes it seem like the fight is really important -- like he is recording the details of some battle that will change the history of the world. But this seems satirical since the battle will change nothing that we humans can discern, at least.
Then Thoreau compares the ants' battles to humans' battles. By comparing them, he seems to be saying that even battles that seem important to us are really no more important in the broader scheme of things than the ants' battle is.