When you're trying to rear Gulf Fritillary butterflies (Agraulis vanillae), expect the expected: predators.
It doesn't take long for European paper wasps (Polistes dominula) to find the butterfly's host plant, the passionflower vine (Passsiflora) and prey. We've seen the wasps, with their long hind legs dangling, follow the butterflies as they flit from tendrils to leaves to lay their eggs. The wasps grab the tiny yellow eggs and squirming caterpillars and rip into chrysalids.
They'll attack adult butterflies, too, especially the crippled ones.
Then off they fly with bits of food--protein--for their colony. Wasps are carnivores (unlike their cousins, the honey bees, which are vegetarians).
The European paper wasp, so named because of its European origin, is relatively new to the United States. Scientists tell us that the P. dominula was not recorded in North America until 1981. P. dominula was first discovered in the United States in the late 1970s near Boston, Mass. This invasive species has since spread rapidly across the country. Entomologists worry that it is displacing the native species of Polistes wasps.
Have you ever seen these wasps attack other insects? Butterflies?
Last Sunday we were watching a crippled butterfly (no doubt crippled by a predator such as a bird or praying mantis) clinging to a Passiflora leaf as males tried unsuccessfully to mate with her. Eventually, the males all fluttered away and a European paper wasp patrolling the area zeroed in for the attack.
Like a hungry lion singling out a crippled gazelle from a stampeding herd, the European paper wasp knew just what to do.
Your mother laid an egg, you hatched into a caterpillar, and you're eating as much as you can before you spin into a chrysalis and then emerge, as a butterfly, ready to start the life cycle over again.
You are not aware of the European paper wasp, its long legs dangling, moving through the leaves and eating the newly laid eggs around you. The wasp lurks in the deep, dark shadows as you finish one bite and reach for another.
Then you see the predator coming after you.
It does not end well for you. You have become protein for the wasp to feed its young.
For several weeks now, the European paper wasps (Polistes dominula) have wreaked havoc on the Gulf Frit population on our Passiflora. Sometimes they pair up in twos, sometimes in threes and fours, and once a horde of five descended
They follow the fluttering butterflies as they touch down on a leaf to lay an egg. Then they eat the eggs, kill the caterpillars, and tear apart the chrysalids.
European paper wasps are relatively new invaders from Europe; they were first spotted in the United States in 1981 in Massachusetts. They are now colonizing the entire country, taking over the native wasps' territory.
There's good news and then there's bad news. If you like having European paper wasps around to prey on the larvae of hornworms, cabbageworms and tent caterpillars, then you may consider them beneficial insects. But if you're trying to rear a few butterflies, such as the Gulf Fritillaries (Agraulis vanillae), then they're Public Enemy No. 1.
Studies show that they can also be cunning.
According to an article out of Michigan State University: "A Cornell University researcher has found that certain female wasps, without nests of their own, 'sit and wait' for an opportunity to adopt an orphaned nest or hijack a nest from another queen. These sit-and-wait female wasps prefer to adopt the most mature nests, probably because these nests will produce workers the soonest, and colonies with workers are very likely to survive. Once a queen adopts a nest she will eat the former queen's eggs and young larvae and replace them with her own eggs. The older larvae and pupae, which belonged to the former queen, are allowed to complete development and may eventually help rear the adopting female's offspring. Ferocious hunters, paper wasps feast on caterpillars."
"The nests are usually founded by a single Queen or Foundress, who starts her nest in May having hibernated as a mated queen throughout the winter often in the company of all the other mated females from their parental nest."
See photos of European paper wasps on BugGuide.net.
Meanwhile, we figure that only about 10 percent of the Gulf Frit eggs will ever make it into butterflies--no thanks to assorted predators.
But a few will make it, and what spectacular butterflies they will be!
People aren't the only ones favoring fava beans.
Fava beans growing in a raised bed in the Häagen-Dazs Honey Bee Haven on Bee Biology Road, UC Davis, are attracting honey bees, European paper wasps, lacewings, ladybugs, aphids and carpenter bees.
We saw all six insects on a trip to the haven last Friday.
While the honey bees and carpenter bees gathered nectar, the European paper wasps, lacewings and the ladybugs searched for prey. The ladybugs were also searching for mates.
The half-acre bee friendly garden, located next to the Harry H. Laidlaw Jr. Honey Bee Research Facility, west of the central campus, is open year around from dawn to dusk. Admission is free. Visitors can conduct their own self-guided tours by following the signs and reading the plant labels. Groups that want a guided tour (the cost is $4 per person) can contact Christine Casey at firstname.lastname@example.org.
Meanwhile, life is good in the fava beans.
An anise swallowtail fluttered in and out of the tall anise bordering the banks of the Benicia Marina.
A beautiful sight.
The female butterfly (Papilio zelicaon), as identified by butterfly expert Arthur Shapiro, professor of evolution and ecology at the University of California, Davis, was probably laying eggs, he told us.
The butterfly is often confused with a Western tiger swallowtail (Papilio rutulus). Their coloring does indeed look similar.
As for the anise butterflies, "they have several generations (late February or March-October) and breed very largely on sweet fennel ("anise"), Foeniculum vulgare, and (in the first half of the season) poison hemlock, Conium maculatum," Shapiro writes on his popular website, Art's Butterfly World. "Both of these are naturalized European weeds."
The larvae of the anise swallowtail use fennel as a food plant. Something else about anise: If you crush the leaves, they smell like licorice.
While we were watching the anise swallowtail, something else was watching her: an European paper wasp.
Wasps eat butterfly eggs.
The first day of spring--Tuesday, March 20--yielded a diversity of insects in the fava beans planted in the Häagen-Dazs Honey Bee Haven, a half-acre bee friendly garden adjacent to the Harry H. Laidlaw Jr. Honey Bee Research Facility on Bee Biology Road, University of California,Davis.
A flurry of insects joined the honey bees: ladybugs, a blow fly, a stink bug, an alfalfa butterfly, European paper wasp and scores of aphids.
Fava beans (Vicia faba), one of the world's oldest cultivated crops and native to the Mediterranean region, are also known as broad beans, horse beans, pigeon beans, and the like.
"In North America, Canada is perhaps the largest producer of fava beans since they produce best in cool summer areas," write San Joaquin County Farm Advisors Gary Hickman and Mick Canevari in a Family Farm Series publication of the UC Davis Small Farm Center. "Minnesota and the lake states produce small acreages. In California, fava beans are grown as seed crops along the coast from Lompoc to Salinas and in the Northern Sacramento Valley, but in other areas of the state they are grown mostly as a cover crop or for green manure."
You can learn more about fava beans in the UC Davis Small Farm Center publication. Meanwhile, the insects hanging out in the Häagen-Dazs Honey Bee Haven are definitely favoring the fava beans.