What a shame that you're squishing them! Some of us like the caterpillars and ensuing butterflies better than the vines!
Where do you live, and what type passionvine are you growing? The favorite passi of gulf frits is p. incarnata/maypops, so I'd recommned you plant some of that in an out of the way place for the butterflies, and plant something they don't like as well in your favorite spot. Mine don't like p. caerulea nearly as well as many others - I've also ordered some new passis, p. loefgrenii, p. reflexiflora, and p. 'Anastasia' that they haven't touched, even though they're making new growth all over the fence their pots are near. They also don't like my p. biflora very much, but they'll use it/lay eggs on it after they've eaten everything else down to a nub. Others on this forum might tell you which of their passis the gulf frits don't like.
Sherry

I started planting passies with the hope of attracting Gulf Frits. Well, 25 passies later still no GF's but I'm not giving up. Don't squish them, go get more passifloras. They are beautiful caterpillars as well as beautiful butterflies.
Karyn

Actually, if you really don't want the caterpillars and the beautiful butterflies, you probably shouldn't be planting any type of passionvine - gulf frits can and will eventually eat just about any type if there's nothing they like better left.
There are many other beautiful flowering vines you could plant, depending on where you live.
Sherry

I normally leave them alone--once the vines are stripped, the butterflies stop laying eggs and the caterpillar population goes into steep decline. After a few weeks, the vines will recover and leaf out again. By then, fall is just around the corner and butterflies/caterpillars aren't much of an issue.

They'll eat incarnata and incarnata hybrids happily, and also eat caerulea and caerulea hybrids if the former isn't available. Pure red passiflora species, such as coccinea and vitifolia are unsuitable as Gulf frit hosts, and although caterpillars will munch on them, they never survive to maturity.

If you must control the caterpillar populations (and boy, they've ticked me off to no end at times--particularly when they girdle branches) your best bet would be to go with BT. That's an organic bacteria that kills caterpillars but leaves other insects alone. It has a low impact on the environment and is favored by green gardeners.