Wild About Texas – October, 2007

I know no gardener who detests butterflies in the garden, but I know many who wish their plants weren’t all chewed up by those awful “worms”! Before you go pinching those worms off your plants, make an effort to identify what you have. Often your pest is just a pest (from a gardener’s perspective), but you may find you have a butterfly larva, or caterpillar.

How does one know a butterfly caterpillar from other things? Upon close examination, a caterpillar will have a discernable head accommodating chewing mouthparts, three segments of the thorax where three pairs of true legs are located, and ten abdominal segments that will support four or five pairs of “prolegs”. True legs and prolegs look different and are separated by a few segments of the abdomen.

Butterflies and moths are closely related, belonging to the insect order Lepidoptera. The larval stages of both are called caterpillars, which look very similar and can be difficult to tell apart. As a generalization, butterfly caterpillars are smooth or spiny whereas moth caterpillars can be smooth or “furry”. Be careful when handling any caterpillar with hairs or spines, some can impart a startling sting.

Another way to attempt identification of a caterpillar is to do some sleuthing. Knowing the plant on which you find the larva can give you significant clues for identification. Most caterpillars are rather picky about what plants they will eat, often limited to a single plant genus or family. Others are generalists. For example, the Common Hairstreak larva is known to feed on more than 20 plant species. Good field guides for moths and butterflies will indicate the preferred larval food plant(s). Once you narrow down the possibilities, compare your creature with pictures in books or on the Internet.

If you want to make your garden appealing to a variety of butterflies, plant a variety of native plants, including so-called “weeds.” Giant ragweed, for instance, may not have any apparent beneficial qualities but it does feed young Bordered Patches. Nettles feed Red Admirals. You’ll have to decide how much chewing by caterpillars you are willing to tolerate in your garden.

Be aware when applying insecticides (organic or synthetic) that non-target species can be and are affected. Caterpillars as well as kids and pets are vulnerable. If you are trying to eliminate a particular species of Lepidoptera (such as webworms or oak leaf rollers), B.t. (Bacillis thuringiensis var. kurstaki) is a biological control that is non-toxic to other organisms, but can hurt nearby desirable butterfly or moth populations.

When deciding whether to save, spray, or squish, don’t disregard the moths. Often they are colorful, boldly patterned, and, as in the case of the Cecropia that can have more than a 6-inch wingspan, they are sometimes quite large and can be beautiful in their own right.

Below is a list of Texas native plant groups with the names of butterflies or moths that use the plants for nourishment during their caterpillar stage:

Wafer Ash, Prickly Ash, other citrus (Ptelea, Zanthoxylum); Giant Swallowtail (Heraclides cresphontes)

Prairie parsley, Dutchman’s Breeches (Polytaenia, Thamnosma); Eastern Black Swallowtail (Papilio polyxenes)

Senna, Cassia (Senna, Cassia); Cloudless Sulphur (Phoebis sennae)

Passionvines (Passiflora); Gulf Fritillary, Zebra Longwing (Agraulis vanillae, Heliconius charitonius)

Sunflowers, Ragweeds, others (Helianthus, Ambrosia); Bordered Patch (Chlosyne lacinia)

Nettles, Pellitory, others (Urtica, Perietaria); Red Admiral (Vanessa atalanta)

Gerardia, Toadflax (Agalinis, Linaria); Common Buckeye (Junonia coenia)

Hackberry (Celtis); Hackberry Emperor (Asterocampa celtis)

Milkweeds (Asclepias); Monarchs, Queens (Danaus plexippus, Danaus gilippus)

Plum, Willow (Prunus, Salix); Cecropia (giant silkworm moth)(Hyalophora cecropia)

For more information about Texas native plants, visit the Wildflower Center’s web site at www.wildflower.org.

About the author: Andrea DeLong-Amaya is the Director of Horticulture at the Lady Bird Johnson Wildflower Center in Austin.

Posted by Neil Sperry
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