In her latest post, Jean Godawa helps us to identify the caterpillars that will
mature into beautiful butterflies.
I've often heard the expression that beauty is pain. It's usually in relation to some cruel female fashion choices like waist-cinching corsets or high heels. But it is an accurate and helpful mantra for those of us who want to welcome some flittering wildlife into our gardens.
|Tiger Swallowtail (Papilio glaucus)|
Of all the garden insect fauna, butterflies are most synonymous with beauty. Their delicate, colourful wings with striking patterns and their gentle flight as they move among garden plants make it hard to believe that these lovely beauties are in the same class as dung beetles or cockroaches.
In order for us to see the beauty of butterflies in our gardens, we must also put up with the pain of their immature forms. Caterpillars, the larval form of butterflies, are vilified as plant slayers, often for good reason. Their voracious appetite can severely damage garden plants. Large groups of them can defoliate a forest.
|Defoliation in a Colorado aspen/poplar forest by western tent caterpillars (Malacosoma californicum)|
In our enthusiasm to protect our plants from any leaf-munching critter, we pick caterpillars off plants, or worse, spray them with insecticide. In doing this, we might inadvertently destroy a beloved creature that would have otherwise been flitting about our garden a few weeks later, pollinating our flowers and adding to the beauty of the space.
Recognizing and identifying the larval forms of butterflies can help prevent this and ensure that these beautiful creatures continue to visit our gardens.
The easily recognizable monarch butterfly (Danaus plexippus) is common throughout North America and is known for its ability to migrate thousands of kilometers to wintering sites in Mexico and California. This discovery and the subsequent work on monarch migration has alerted us to issues such as climate change, the overuse of pesticides and the destruction of sensitive habitats.
If you have any milkweed in your garden you may have seen the larva of the monarch butterfly munching away. It feeds on milkweed exclusively while the adult form feeds on nectar from a variety of flowers. Butterfly larvae have strong mandibles for chewing leaves while adult butterflies eat through a straw-like, nectar-sucking proboscis.
A similar butterfly, the viceroy (Limenitis archippus), is easily mistaken for a monarch. A black band across the hind wings of the viceroy distinguishes it from the monarch. The colour of these butterflies gives them a protective advantage. Monarchs are toxic to birds that eat them. While viceroys are not toxic, their colouring scares away potential predators.
Despite the viceroy butterfly's resemblance to the monarch, its larva is quite different. Viceroy larvae feed on fruit trees as well as birch and poplar.
The young larva is black with a white "saddle" in the middle. As the larva matures, it becomes smoother in texture and its colouring becomes light green with black and white stripes while maintaining the orange spots. You may find these caterpillars in your dill, parsley or carrot plants. Healthy, mature plants can usually tolerate some caterpillar feeding. Keep an eye on your plants if you've seen one of these larvae on it. Chances are it will pupate before it causes any serious damage.
The spicebush swallowtail butterfly (Papilio troilus), which closely resembles the eastern swallowtail as an adult, has a very different larval form. The young larva looks a bit like bird droppings, making it unappetizing to predators.
As the larva eats and grows, it has a much different and striking appearance, with bright colouring and large eyespots. This creature typically feeds on trees in the Lauraceae family including sassafras and spicebush.
The question mark butterfly (Polygonia interrogationis) can be found east of the Rocky Mountains and it typically feeds on elm and basswood. It is named for the small, white question mark on the underside of each of its hind wings, visible when the butterfly's wings are upright.
Question mark larvae can look very intimidating with their spiny clubs. While some caterpillars with hairs or spikes release a venom when touched, the question mark caterpillar is harmless.
Both moths and butterflies belong to the same group - Lepidoptera, but there are a few ways to tell the difference between the two.
- Butterflies generally have thin or wire-like antennae with knobs on the end while moth antennae are often feathery or hairy
- Butterflies rest with their wings outstretched or folded up over their back so that the underside is visible; moths rest with their wings flat or tented over their body
- Moths are typically nocturnal while butterflies are active through the day (diurnal)
Cabbage white larvae are serious pests to their host plants. This might be one of the "pains" that your garden should not endure. Hand remove these caterpillars from your veggies and drop them in a bucket of soapy water.
|Buckeye Butterfly (Junonia coenia)|
With well over 10,000 Lepidoptera species in North America alone, it can be challenging to identify the adult or larva in your garden. Before destroying a caterpillar, try to identify it. You may decide to put up with the little "pain" to have the "beauty" a few weeks later.
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About Jean Godawa: Jean is a science teacher and writer. She has been writing science-related articles for print and online publications for more than ten years. Jean holds a degree in biology and environmental science with a focus on entomology from the University of Toronto. She had conducted field research in the tropical rainforests of Asia and South America.
More information and Links:
There are some wonderful field guides available to help identify caterpillars. I have some well-worn books that I frequently use for insect identification. My favorite though is a very simple field guide for novice entomophiles: Peterson First Guides Caterpillars by Amy Bartlett Wright and Roger Tory Peterson. (Not an endorsement, just a personal preference. Jean).