Gardening for Wildness: Garden Wasps

A recent tally of threatened species by the World Conservation Union lists more than a thousand mammals, nearly a quarter of all those we know, and more than a thousand birds.  Each year’s list is longer.  We can reverse those trends…by living more lightly and by making way for wildness in our yards and parks and forests and farms.  Nothing keeps us from doing so, except habit and haste and lack of faith.  Faith in what?  In our capacity for decent and loving work, in the healing energy of wildness, in the holiness of creation.”

– Scott Russell Sanders, Earth Works (2012)

Noted Harvard biologist and Pulitzer Prize-winning author Edward O. Wilson coined the acronym HIPPO to represent the five human-induced causes of biodiversity decline on Earth: habitat destruction, invasive species, pollution of all types, human population growth, and over-harvesting.  The HIPPO juggernaut continues to roll along, unabated, with the exception of some gardens, those special places that offer refuge to countless species of insects, birds, amphibians, rodents, small mammals, and the bacteria and fungi that inhabit garden soils.

A bald-faced hornet foraging on raspberry blossoms.

A bald-faced hornet foraging on raspberry blossoms.

Some influential horticultural magazines, along with many public gardens, continue to focus on gardens that do not offer refuge for wildness, gardens planted to nonfunctional non-native plants chosen solely for photographic appeal, gardens devoid of life, where any chewed leaf is quickly cut away, every caterpillar and beetle quickly dispatched.  I wish it were otherwise, as these publications and public gardens could be showcasing truly functional gardens devoted to the preservation of wildness in all its forms.

I propose another name for the ecologically-functional garden, “garden refuge”, and I  wait impatiently for the garden publication that focuses on such gardens, a publication with images of caterpillars chewing on leaves, pollinators foraging for pollen and nectar, predaceous wasps capturing their prey, trees filled with birds.  I imaging a magazine filled cover to cover with articles that offer advice on the most ecologically functional plants for a given region, one that spotlights the life cycles of garden creatures.

A yellowjacket foraging on raspberry flowers.

A yellowjacket foraging on raspberry flowers.

As one who gardens for wildness, I spend as much time observing as cultivating.  I am preoccupied with the insect life in our garden, an amateur entomologist with numerous mistaken identifications to his credit, but no less amazed at the diversity of insect life in the garden and the  degree to which these little creatures determine my success as a gardener.  This past garden season, for example, I became fascinated by the diversity of garden wasps.

Wasps are often referred to as “incidental pollinators”, insects that as adults move around a few grains of pollen as they forage for nectar, perhaps dropping a grain on a stigma in the process.  Most species are smooth-bodied and thus cannot actively collect pollen from the flowers they visit and those with hairs lack the branched pollen-trapping hairs of bees and thus are limited in the amount of pollen that they can collect.

A great black wasp foraging on swamp milkweed blossoms.

A great black wasp foraging on swamp milkweed blossoms.

Many adult wasps are also predators, capturing insect larvae, mainly caterpillars, to feed their own larvae.  Or they are parasitoids, laying their eggs either in or on an insect host that will become food for the wasp larvae.

Wasps are the closest relatives of bees, an evolutionary relationship best summed up by the statements, “bees are wasps that adopted a vegetarian diet” and “bees are wasps with hairs”.  Wasp larvae are carnivorous, feeding on insect prey captured by their mothers, including plant-damaging herbivores and bits of meat scavenged by their mother from animal carcasses.  No longer in need of so much protein, the adult wasp switches to a high carbohydrate diet fueled by nectar and rotting fruit.

A sand wasp (Ammophila procera) foraging on achillea flowers.

A sand wasp (Ammophila procera) foraging on achillea flowers.

As foragers, wasps are limited by a relatively short tongue, unable to reach the nectar of many flowers.  In our garden we find them on shallow flowers like those of goldenrod, raspberry, and members of the carrot family, including Queen Anne’s lace.

I admit to being intimidated by the large wasps that frequent our garden in summer, the bald-faced hornets that forage nectar from raspberry blossoms or the yellow jackets that swarm over ripe blueberries.  They seem docile when so preoccupied, yet I recall incidents in my youth when too much interest in these creatures resulted in painful stings.  So I give these social wasps a wide berth, thankful that their nests remain undiscovered.  The solitary hunting wasps, such as the smaller sand wasps discussed below, are less intimidating, largely due to a lack of negative experiences with them.  As for the parasitic wasps that are so helpful in controlling garden herbivore populations, most are so small as to seem harmless, and so far they have allowed close scrutiny without incident.

A sand wasp (Eremnophila aureonotata) foraging on goldenrod flowers.

A sand wasp (Eremnophila aureonotata) foraging on goldenrod flowers.

At the forefront of regulating herbivores (plant munchers) in the garden are numerous species of parasitic wasps, many no larger than a grain of rice.  Most attack immature insects, including caterpillars and other larvae.  Because feeding by the wasp larvae results in the death of the host, these wasps are called parasitoids, distinguishing them from the true parasites that do not kill their hosts.

Well represented in Marjorie’s Garden are parasitoid thread-waisted wasps, so named for the thread-like anterior end of the abdomen.  Common names associated with this group include sand wasp, digger wasp, mud wasp, hunting wasp, caterpillar-hunter, and cicada killer, all indicators of members’ life styles.  Most nest in the soil or mud and most adults are solitary hunters of other insects, often caterpillars, feeding their prey to their larvae.  Two species included in this group, the great black wasp, Sphex pensylvanicus, and a sand wasp, Ammophila procera, were both subjects of earlier columns (http://bangordailynews.com/2011/08/19/living/harvesting-all-that-the-august-garden-has-to-offer/?ref=search).  They are common in our garden along with a third species, Eremnophila aureonotata, often seen foraging on goldenrod.  The female E. aureonotata is uniquely striking, blue-black with silver markings on her thorax.  All three species are caterpillar hunters, providing each of their larvae with a single caterpillar, typically of a moth or skipper butterfly.

A pelecinid wasp (Pelecinus polyturator) taking a break from foraging.

A pelecinid wasp (Pelecinus polyturator) taking a break from foraging.

Perhaps the most unusual wasp we have encountered in the garden is Pelecinus polyturator, the American pelecinid wasp.  The first time I saw one in flight, I took it for a damselfly gliding slowly through the air on short wings, sporting long antennae and a long curved black tail.  After several hours searching images on the Internet, I finally identified the creature as a most unusual wasp, the long tail her abdomen, five times the length of the rest of her body.

While the adult pelecinid is a nectar feeder, its larva is a parasitoid, living off of the paralyzed body of its host, the underground grub of a Japanese beetle or other June beetle, killing it in the process.  It begins with the female wasp exploring the soil with her long abdomen to determine the presence of the grub.  She then deposits an egg directly into the beetle larvae and moves on.  When the egg hatches, the wasp larva feeds on the grub’s tissue until time to pupate.

Male pelecinids are so rare in certain regions of the species’ range that the females have adapted the means to reproduce without them, a process termed parthenogenesis.  In areas where males are more numerous, normal reproduction occurs.

As for the sting, I’m told it is a pinprick.

A cuckoo wasp, often mistaken for a solitary bee.

A cuckoo wasp, often mistaken for a solitary bee.

Sometimes it is difficult to tell a wasp from a bee.  I spent many hours trying to identify from a photo what I assumed to be an emerald green solitary bee foraging on Queen Anne’s Lace, finally discovering that it was one of 230 species of cuckoo wasps, so called because they lay their eggs in the nests of other solitary wasps or bees, consuming the host’s provisions and often the host’s larvae.  I had overlooked one of the key features that distinguish bees and wasp, the lack of hairs on the latter.

If you choose to garden without chemical poisons, you are likely to find the wasp species listed above in your garden, working hard to reduce populations of caterpillars and other garden herbivores.  All you have to do is spend a little time looking for these creatures, often finding them foraging on flowers.  It is time will spent, for it keeps you in touch with the holiness of creation.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: http://www.facebook.com/pages/The-New-England-Gardeners-Year/187285218055676.)