Obtain some commercial ant baits then figure out how and where you can place them not accessible to the dog. Perhaps under some sort of cage of hardware cloth?

Where in the world are you and which ant species do you have? Most ants are recyclers of dead and decaying stuff, although there are those that will attack and eat living critters of many kinds, not many of them live in the USA.

kimmq is kimmsr

(I can't see that DE would be effective with ants unless an area is blanketed with it.)

Are you in an area where fire ants are common? That is certainly one ant species that will attact and eat caterpillars and pupae. But so will others. Ants will also feast on butterfly and moth eggs.

My recommendation for ants would be a bait, as well. For fire ants and some other species, Amdro is extremely effective. It is applied in very small amounts on the ground where the particles are quickly taken by ants into their chambers where it is eventually shared with the community.

If applied properly according to label directions, Amdro is safe to use around pets and caterpillars. You can watch the particles be taken away by the ants in a matter of moments.

I'm in North Carolina and we don't have fire ants in my area. I believe that they are carpenter ants.

So far a thick ring of baby powder around their plants has worked well. It has to be reapplied after it rains, but doesn't blow away.

Classic, but good. I've been in more than one research labs that rear insects in TX that have to supplement things like "doors that seal" with a line of baby powder. Fire ants are fun.

The following is simply pure peculation, but previous replies have been concerned only with controlling the ants, whereas I am looking at a different aspect of your original post. That said - Are you certain the ants actually are eating the caterpillars?? Perhaps
something like the following is going on – although swallowtails are NOT the caterpillar
species associated with ant activity. (See below.)

[Or perhaps the question to ask is -- are you certain your caterpillars are swallowtail larvae? I'm sorry to suggest it since the larvae of Papilionidae & Lycaenidae families are very different in appearance & size!]

Here is an excerpt from Wikipedia (I know, but…sometimes…)

"A myrmecophile is an organism that lives in
association with ants. Myrmecophiles may have various roles in their
host ant colony. Many consume waste materials in the nests, such as dead ants,
dead larvae, or fungi
growing in the nest. Some myrmecophiles, however, feed on the stored food
supplies of ants, and a few are predatory on ant eggs, larvae, or pupae. Others
benefit the ants by providing a food source for them. Most associations are
facultative, benefiting one or both participants but not being necessary to
their survival, but many myrmecophilous relationships are obligate, meaning one
or the other participant requires the relationship for survival.

Myrmecophilous associations are
best known in butterflies of the family Lycaenidae.
Many lycaenid caterpillars produce nectar by specialized organs and communicate
with the ants through sound and vibrations.[7] The association with ants is believed to
reduce the parasitisation of the butterfly caterpillars.[8] "

And
even though this video from National Geographic concerns completely different
butterfly species, it is fascinating to watch, none the less! Caterpillar-ant symbiosis

Nature is endlessly and wondrously fascinating, mysterious, and obscure!