An Eastern tiger swallowtail

Native Delaware

Butterfly season only average, according to UD entomologist and others

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9:20 a.m., July 17, 2012--Brian Kunkel’s weekend strolls at Middle Run Natural Area make him see red – not because he’s angry but because the red admiral butterfly has been abundant at this 850-acre park east of Newark. A large, red-banded butterfly, the red admiral has been seen in large numbers throughout Delaware this summer.  

“The red admiral is experiencing an irruption – a rapid and irregular increase in population numbers,” says Kunkel, an entomologist with UD Cooperative Extension. “It’s not just here in Delaware; this irruption also has been reported in New Jersey, the Poconos, western New York and other Northeastern locales. The last time a red admiral irruption was seen locally was 2001.”

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The red admiral is the bright spot for Delaware butterfly watchers this summer. All in all, it’s shaping up to be just a so-so season for butterflies.

“Butterfly numbers were good at the end of May and into June but then things really backed down,” says Sheila Vincent, a group program coordinator for the Delaware Nature Society who maintains Ashland Nature Center’s Butterfly House. 

“Mid-July to mid-August is typically the peak of butterfly activity in Delaware but we’ve seen fewer individuals flying,” says Vincent, “Right now, I don’t think we’re going see a repeat of 2011 and 2010, both of which were very good years for butterflies.”

Butterfly populations are influenced by a complex interplay of temperature, moisture and food supply. Different species are impacted by different factors. For example, a species that overwinters in the adult form – such as the mourning cloak -- will have better survival rates in milder winters, says Kunkel. If the butterfly’s host plant flourishes during a rainy spring, odds are that butterfly will do well that season, too.    

“With so many factors influencing population density, I can’t begin to speculate on why overall butterfly numbers appear lower this year,” says Kunkel.

Delaware has about 120 species of resident breeding butterflies. Considering that most states have about 100 species, Delaware is a pretty good spot for butterfly watching.       

“Delaware is home to both the Piedmont Plateau, in the north, and the Coastal Plain, in the middle and southern parts of the state. This makes for a greater diversity of butterflies,” says Vincent. “For example, we don’t get cloudless sulphur butterflies in the Piedmont but on occasion you see a straggler cloudless sulphur fly up from the Coastal Plain.”   

If you want to attract butterflies to your yard, Kunkel has two important tips. “First, get lots of plants that caterpillars like,” he says. “Gardeners tend to focus on nectar plants that provide adult butterflies with energy but you also need plenty of food sources for caterpillars – the next generation of butterflies.”

Most caterpillars eat only one specific plant or from one plant family. Do your research. If you love the great spangled fritillary butterfly, plant violets, the food source for this butterfly’s caterpillar. If it’s Eastern tiger swallowtails that you’re trying to attract, plant tulip poplar, sweetbay magnolia and black cherry trees.  

If you’ve always prided yourself on a flawless, neat-as-a-pin garden, you may not like Kunkel’s second piece of advice – “tolerate insect feeding.”

Caterpillars eat the leaves and stems of plants, which mean, of course, little holes on the leaves of your plants. “If you want to enjoy the sight of the pipevine swallowtail butterfly, with its brilliant blue wings, you’ll have to accept that your pipevine plants are going to get chewed up a bit by this butterfly’s caterpillars,” says Kunkel.

At the University of Delaware Botanic Gardens, feeding the caterpillars is seen as just as important as feeding the butterflies. The gardens’ Lepidoptera Trail, which opened in 2009, features a wide range of plants to attract caterpillars.   

“The trail is not a butterfly garden, which is designed to attract butterflies to feed on nectar,” says garden director John Frett. “It is an ecosystem to attract Lepidoptera throughout their life cycle. It’s a place for them to lay their eggs, which become larvae or caterpillars before entering the inactive pupal stage and then emerging as butterflies, moths or skippers.”

Besides, caterpillars are cool in their own right. “Take the caterpillar of the spicebush swallowtail butterfly. It looks like something out of a cartoon,” marvels Kunkel.

This caterpillar features oversized fake eyes on its thorax and is a garish neon green color at certain stages of development. The fake eyes and bright color is supposed to make the caterpillar look like a snake and thus scare away birds and other predators.

The Lepidoptera Trail, as well as the rest of the UD Botanic Gardens, is open daily from sunrise to sunset for free self-guided trails. For more info, go to http://ag.udel.edu/udbg or call 302-831-0153.  

Article by Margo McDonough

Photo by Brian Kunkel

 

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