We people have a special regard for butterflies; we love 'em. They signify many powerfully positive things in our traditions and literature: the immortal soul, freedom, beauty, summer's bounty. So it's not surprising you feel honored when such a majestic butterfly deigns to visit your space. It's especially nice when you happen to have your camera ready. This is Papilio rutulus, the western tiger swallowtail. This particular one glided in gracefully over the border hedges and spent a long time feeding at the red pentas. I could hear sweet strains of Vivaldi starting up in the shrubbery as my eyes glazed over in adulation.
But wait. What about the caterpillars? Like most insects with complete metamorphosis, butterfly young feed on a different food source than the adults. This is a brilliant adaptation of the "don't put all your eggs in one basket" strategy. All caterpillars eat plants. Voraciously. But few butterfly species are listed as serious pests. The european cabbage and common white caterpillars (genus pieres) cause a lot of damage to plants in the cabbage family. The giant swallowtail caterpillar (papilio cresphontes) is a pest on citrus trees. However moths (kin to butterflies and in the same family) are seemingly so bad, and so reviled even their common names depict wrack and ruin:check out some moth caterpillars listed as agricultural and domestic pests. Moths are mostly nocturnal, and metaphors for death, spooks, and Hannibal Lector. Are moths really the dark side of the family lepidoptera, or does our human bias in favor of butterflies make it seem so? You'll rarely read an ode to a moth performing its nightly pollination duty.
The larvae of Papilio rutulus are said to feed on tree leaves, including sycamore, willow, poplar and alder. I'm going to make a point to check for the level of swallowtail caterpillar damage in sycamore trees nearby.