Khew et. al. There is no doubt that the butterfly push (color variations aside) is a powerful magnet for local species of butterflies. It does have a strong odor that attracts quite a few skippers, swallowtails, monarchs, and hummingbird moths. It also attracts the European hornet, not because of the necter, but rather because of the butterflies that it targets. I've photographed a few attacks: extremely vicious.

Now, a fragrant source of nectar should appeal to any butterfly. Why U.S. species find it attractive and your local species do not, is curious. Perhaps there are so many other sources of fragrant necter in Singapore? We have a couple other imported varieties of Asian plants, bushes, and trees that give off a strong, pleasant odor when in bloom and they too attract a variety of native species that should -- logically -- have evolved to favor native sources of nectar over imported, non-native species. Perhaps some of our esteemed colleagues could contribute a thought or two about sensory behavior of your butterflies... or those of butterflies in general.

In human terms (I understand the danger of linking human behavior to non-human species) it's possible that some insects like a different taste. Something new and novel. David, for example, likes durian (I have yet to try durian, but will keep you informed), but may have grown up with Kiwi fruit. Perhaps those raised with durian might enjoy bananas from Costa Rica or apples from Washington State.

Always appreciate the interesting exchanges of views.

Wiliam