An Underappreciated Insect: The Syrphid Fly

Toxomerus occidentalis, female slurping nectar on Erigeron specious (showy fleabane)

Toxomerus occidentals (female), soaking up nectar on showy fleabane (Erigeron specious)


Beneficial in many ways, syrphid flies — also called flower flies — 
are true flies in the order Diptera, family Syrphidae. Some can be recognized by their ability to dart around as well as hover in the air in one place, wings nearly invisible, as they search for flowers on which to feed—somewhat like a tiny helicopter, but with much more grace (this flair led to their other common name, hover fly). They come in various shapes and sizes (typically 1/4 to 3/4 inch in length); the tiny ones require a hand lens or macro lens to get a good look. And when you do, you’ll be amazed at the beautiful patterns and bright colors that often serve to mimic dangerous looking bees or wasps and fool predators like birds into leaving them alone (but don’t worry, they couldn’t sting you if they wanted to!).

Syrphids in the genus Spilomyia often mimic wasps, with vivid yellow and black patterns and modified antennae.

Syrphids in the genus Spilomyia often mimic wasps, with vivid yellow and black patterns and modified antennae.


Multi-functional

Not needing to carry and store pollen for their young (like most bees do) doesn’t prevent them from being extremely important pollinators. Researchers have found that although syrphid flies pollinate less effectively per flower visit, they visit flowers more often, resulting in essentially the same pollination services as bees. And, it’s thought that they may be more tolerant of the landscape changes that we humans insist on, than bees are.

But syrphid flies are not only important as pollinators in gardens, organic farms, and wild areas. During their immature stage, most species that are found in gardens and nearly half of the 6,000 syrphid fly species worldwide are voracious consumers of aphids, scale insects, and other soft-bodied pests. In coastal Central California, researchers compared romaine lettuce sprayed with an insecticide and lettuce without insecticide. They found that syrphid larvae were primarily responsible for suppressing aphids in organic romaine lettuce, and called the sprayed lettuce “unmarketable.” Other types of syrphid fly larvae are either (1) scavengers that tidy up ant, bee, and wasp nests, (2) feeders of plant material, tree sap, and fungi, or (3) decomposers that feed on decaying organic matter. To add to their achievements, larvae are reportedly more effective in cool weather (as in early spring) than most other such predators.

Myathropa florea, male. Larvae feed on bacteria at the base of trees or in decaying leaves.

Myathropa florea, male. Larvae of this species feed on bacteria at the base of trees or in decaying leaves.


Life Cycle

Females lay their tiny, elongated eggs singly on leaves—typically near aphid colonies, so food is within reach—and they hatch in a few days. The tapered, grub-like larvae are blind and legless, but the mouths of these aphid-eaters are equipped with triple-pointed darts that enable them to pierce and suck their prey dry. At maturation, the larvae are promoted to the soil to become pupa and, eventually, adult flies. Their life cycle takes several weeks; reportedly three generations per year are typical in the Northwest. Most syrphid flies overwinter as larvae in leaf litter—yet another reason to not remove fallen leaves from soil!

Close encounters
The best way to spot these helpful, colorful little insects in your garden is to move slowly and quietly, and observe carefully. Sometimes all I have to do is pause next to a group of flat-topped flowers (white or yellow ones seem to be their favorites), and within a few minutes one or two will show up to eat (and to dazzle me—in morning sunlight these exceptional little pollinators shimmer!). I’ve photographed nine different species in my small yard, and I’ve just started. Hopefully I’ll encounter many more of these fascinating little flyers in the years to come.

To avoid confusion with bees and wasps, just remember that syrphid flies have huge compound eyes (which help to determine their gender—female eyes are spaced slightly apart while males’ come together at the top of their head); their bodies are sometimes flatter than bees and wasps; their antennae are usually very short; they don’t carry pollen around like most bees do; they have one pair of wings (unlike bees and wasps that have two pairs). The second pair of wings of flies has been reduced to two little knobs called halteres, which can be seen in the photo below. Halteres function like tiny gyroscopes that allow them to stay balanced by detecting and correcting changes in rotation while flying, and enable their zippy acrobatic flights.

Although the mouth parts of syrphids vary between species, allowing different species to access nectar in differently shaped flowers, their typical mouth is basically a retractable extension with a spongelike tip that can soak up either nectar or pollen. The species that have this can only feed on open flowers that have easily accessible nectar. Some species have a modified mouth that allows them to feed at elongated, tubular flowers.

The halteres can be seen at the base of the wings.

The halteres can be seen at the base of the wings.

 

Conservation
Syrphid flies have been studied very little in the U.S., but European research has shown that species diversity has fallen in areas of intensive human activity. According to the Xerces Society, in Britain, seven of the 22 flies for which Biodiversity Action Plans have been prepared are syrphid flies. Given the substantial loss of pollinators induced by habitat loss, pesticides, nonnative species and climate chaos, and the profusion of others in danger of extinction, there is a definite need to conserve all types of wild pollinator communities.

Providing for these flies is similar to most other pollinators: A variety of flowers from spring till fall for adults, and appropriate habitat for egg laying, larval development, and overwintering. Attract and nurture syrphid flies with a diversity of native plants that provide a lot of nectar and pollen (females need pollen to produce eggs). In the Pacific Northwest, try yarrow (Achillea millefolium var. occidentalis), stonecrop (Sedum spp.), goldenrod (Solidago canadensis), blue-eyed grass (Sisyrinchium spp.), fleabane (Erigeron spp.), white spiraea (Spiraea betulifolia var. lucida), mock orange (Philadelphus lewisii), and aster (Symphiotrichum spp.). The flowers of chamomile, dill, parsley, and other garden herbs with flat-topped flowers are also very attractive to them, as is the pollen of grasses and sedges that’s often available early in the season. Be sure to allow leaf litter and downed wood to remain on soil to help them get through the winter and to provide food for the decomposer types.

Aphid remedy
If you have an aphid problem on some plants, remember that predatory insects that keep pests at acceptable levels need prey like aphids. Always inspect aphid colonies for syrphid fly larvae before even thinking about control, even “organic” remedies. Use only plain water to spray off aphids (that can’t climb back on), but only if necessary. Never, ever use insecticides, to which syrphid flies and other creatures are very sensitive. Usually, just turning your back is the best thing: One summer a large patch of native bleeding heart (Dicentra formosa) in my backyard was absolutely infested with aphids. I decided to let nature take her course—cheering on the ladybird beetles and birds who flourished with the situation. As the leaves died back (as they do naturally when the heat of summer arrives) I forgot about the aphids. The following year there were scarcely any on the bleeding heart, but I found another species of aphid on nodding onion (Allium cernuum); again I did nothing and nature took care of it. The following year the wild onion and bleeding heart were fine, but the aspen trees were stricken. Yet again, ladybugs, lacewings, and several species of songbirds took advantage of the generous buffet. The following year there were no outbreaks in my yard, at least none that I noticed.

 

Syrphus opinator (female) on Spiraea betulifolia var. lucida

Syrphus opinator (female) on white spiraea (Spiraea betulifolia var. lucida)

 

Eristatis male on yarrow (Achillea millefolium var. occidentalis

Eristalis sp. on yarrow (Achillea millefolium var. occidentalis)

 

© Eileen M. Stark 2016

To leave a comment, click on post’s title

 

Northwest Native Pollinator Plants for Late Summer to Fall

Late season pollinator plants

Scientists know that bees are dying for a variety of reasons—pesticides, habitat destruction, drought, climate change, nutrition deficit, air pollution, and so on, which makes us the obvious perpetrator. We can help give back to them (and other pollinators) by growing flowering native plants in our gardens (as well as noninvasive exotics that step in when a native plant isn’t available or feasible), with consecutive blooms from early spring till fall. To provide for many different types of pollinators—from long and short-tongued bumblebees to syrphid flies, hummingbirds, and beetles—offer a variety of flower shapes, colors, and sizes, with smaller plants in groups of at least three of the same species (like a big, obvious “Eat Here” sign). Fragrance is also important for attracting insects to flowers and guiding them to food within the flower, and aiding an insect’s ability to efficiently learn particular food sources.

Below are some native perennials and one shrub that offer food for pollinators from mid or late summer to fall in the Pacific Northwest, west of the Cascades. There are more candidates, but I chose these species because they naturally occur in fairly large parts of the region, are generally easy to grow, and are not too hard to find at nurseries (although you will likely have to call around for availability). I’ve listed them alphabetically with some very basic care guidelines. It’s best to plant them in the fall, just before or as the rain returns.

As always, plan ahead and choose species that fit your light, moisture, and soil conditions, but also choose those that are appropriate to the natural landscape—that is, look to nearby natural areas, and add flora that would likely have grown in your area historically, if possible. You can also check a species’ natural range (to county level) here, or check with your local native plant society chapter or county soil and water conservation district. No fertilizer is necessary and please don’t use any pesticides. Keep them adequately hydrated—by watering deeply and infrequently to promote deep roots—until they’re established (2 to 5 years). Enjoy!

Achillea millefolium var. occidentalis (Yarrow): Perennial. 1-3 feet tall x 1-3 feet wide. Sun to part sun. Not fussy about soil; moist or dry. Spreads by rhizomes or seed. Flat-topped clusters of white, fragrant flowers (pictured below) bloom through late summer. (Not to be confused with the Eurasian Achillea millefolium var. millefolium). Achillea millefolium var. occidentalis

Anaphalis margaritacea (Pearly everlasting): Perennial. 1-3 feet tall x 1-2 feet wide. Sun to part shade. Likes moist soil with good drainage, but can tolerate drought once established. Pure white flowers are often used in dried flower arrangements. Besides providing nectar, it is a host plant for painted lady and skipper butterflies.

Baccharis pilularis (Coyotebush): Evergreen or semi-evergreen shrub. 5-8 feet tall x 6-8 feet wide. Sun to part shade. Tolerates poor soils (but needs good drainage) and is drought tolerant. Flowers aren’t showy and are borne on separate male and female plants (male flowers creamy white; female pale green). Excellent wildlife habitat plant but is deer resistant.

048_Campanula rotundiflora sRGBCampanula rotundifolia (common harebell): Perennial. 1-2 feet tall x 1-2 feet wide. Sun to part shade. Moist to dry, well-drained soil, preferably with a good amount of organic matter. Spreads slowly by rhizomes or seed. Bell-shaped, bluish violet flowers typically bloom through late summer. (pictured left)

Gaillardia aristata (blanketflower): Perennial (short-lived). 1-3 feet tall x 1-3 feet wide. Sun to light shade. Tolerates a variety of well-drained soils; drought tolerant when established. Spreads by seed. Colorful yellow and reddish orange flowers bloom well into fall, especially when dead-headed. Deer resistant.

Solidago canadensis (Goldenrod): Perennial. 2-4 feet tall x 2-3 feet wide. Sun to part shade. Solidago canadensisTolerates wide range of soils; prefers moisture but tolerates drought when established. Spreads by rhizomes or seed. Bright gold, fragrant inflorescences typically bloom well into fall. (pictured right)

Symphyotrichum subspicatum (Douglas aster): Perennial. 2-3 feet tall x 2-3 feet wide. Sun to part shade. Does best in moist soil that is rich in organic matter. Spreads slowly by rhizomes and seed. Lavender-blue daisylike flowers bloom from mid summer until mid fall. (pictured below)

 

 

Douglas aster

 

 

© 2015 Eileen M. Stark

To leave a comment, click on blog’s title

10 Great Northwest Native Pollinator Plants for Summer

Bombus vosnesenskii

In honor of National Pollinator Week, let’s zoom in on the bees and other hard-working pollinators whose lives are dictated by weather, season, and the availability of food, nesting habitat, and overwintering sites.

Nature has provided pollinators with unique ways of gathering nutritious pollen and nectar for their young, and they’re enthralling to watch. But bees and other pollinators are in terrible trouble worldwide due to our presence and actions. We can give back to them by growing flowering native plants in our gardens (as well as noninvasive exotics that are especially attractive to bees, like lavender and sunflower) with consecutive blooms from early spring till fall. But don’t forget to provide for them during all their life stages — not just their adult stage — by leaving the leaves, dead wood, and spent flower stalks to make sure they can get through the winter and have habitat to raise their young. And, no pesticides whatsoever!

If you’ve already included some native plants in your yard, you’re well on your way to providing for a wide variety of wildlife. Offering a variety of flower shapes, colors, and sizes, with smaller plants in groups of at least three of the same species (like a big, obvious “Eat” sign) will help provide for many different types of pollinators—from long and short-tongued bumblebees and syrphid flies to hummingbirdsbeetles and thrips. Below are some Pacific Northwest native herbaceous perennials and shrubs that offer food for pollinators from early to mid or late summer in the Pacific Northwest, west of the Cascades.

The list is just a sampling (read about others in my book or within my blog’s PNW native plant profiles), and the species were chosen because they naturally occur in large parts of the region, are generally easy to grow, aren’t too hard to find at native plant nurseries (although you may need to call around for availability), and attract their fair share of native pollinators. I’ve listed them alphabetically with some basic care guidelines. Fall planting is best, as winter rains begin. (If you’re reading this in springtime, don’t worry—you can plant now, but you’ll definitely need to keep an eye on their water needs during the first couple of summers, at the very least.)

As always, plan ahead and choose plants that fit your light, moisture, and soil conditions, but also choose those that are appropriate to the natural landscape—that is, look to nearby natural areas and add flora that likely would have grown in your area historically. You can also search for a species’ natural range (to county level) here, or check with your local native plant society chapter or county soil & water conservation district. Growing them with associated species that evolved alongside them in nature will help them thrive. No fertilizer is necessary (although a one-time addition of compost such as leaf compost to the soil will add some nutrients and improve soil structure), but do keep them adequately hydrated until they’re established (2 to 5 years). Enjoy!

◊ Achillea millefollium var. occidentals (Western yarrow): Perennial. 1-3 feet tall x 1-3 feet wide. Sun to part sun. Not fussy about soil; moist or dry (will spread faster with more moisture). Spreads by rhizomes and seed. Flat-topped clusters of white, fragrant flowers bloom nearly all summer. (Not to be confused with the Eurasian Achillea millefolium var. millefolium).

Asclepias speciosa or A. fascicularis or A. cordifolia (milkweed) : Perennial. 2-3 feet tall x 2-3 feet wide. Sun to part shade. Moist, well-drained soil, but can handle some drought when established. Rounded clusters of soft pink, fragrant flowers. Check out the Xerces Society’s info on milkweed of Oregon and of Washington. (A. fascicularis is pictured, right)Asclepias fascicularis

Campanula rotundifolia (common harebell): Perennial. 1-2 feet tall x 1-2 feet wide. Sun to part sun. Well-drained, moist to dryish soil. Spreads slowly by rhizomes or seed. Bell shaped, violet-blue blossoms.

Ceanothus velutinus (snowbrush): Fast growing evergreen shrub. 6-12 feet tall x 6-12 feet wide. Sun to part shade (intolerant of full shade). Rich or poor soil; very drought tolerant. Dense pyramidal clusters of tiny, fragrant white flowers. Occurs mainly at mid to high elevations; check natural occurrence, to county level, here.

Erigeron speciosus (showy fleabane): Perennial. 2 feet tall x 2 feet wide. Sun to part shade. Well-drained, moist to dry soil. Lovely and abundant daisy-like, bluish lavender blossoms go nearly all summer. (pictured below)

Erigeron speciosus

Holodiscus discolor (oceanspray, aka cream bush): Fast growing, very attractive deciduous shrub. 8-16 feet tall x 8-12 feet wide (larger on protected sites, smaller on windy, harsh sites). Sun to part shade (intolerant of full shade). Not fussy about soil; moist or dry. Drought tolerant when established. Lavish, feathery plumes of creamy-white flowers in early to mid-summer. Nice for hedgerows. Controls erosion.

 

Lupinus polyphyllus (large-leaved lupine): Perennial. 2-4 feet tall x 2-4 feet wide. Sun to part shade (intolerant of full shade). Moist soil preferred but will tolerate short dry periods. Tall spikes of bluish-purple, pea-like flowers. (pictured, right) Lupinus polyphyllus

Sedum spathulifolium or S. oreganum (stonecrop): Perennial. 1-4 inches tall; spreads slowly. Sun to part sun (afternoon shade is welcome). Well-draining, gritty, lean soil. Bright yellow star-shaped flowers. Nice for rock gardens. Not a ground cover for foot traffic. (S. spathulifolium pictured below)

Symphoricarpos albus (snowberry): Deciduous shrub. 4-6 feet tall x 4-6 feet wide. Sun to mostly shade. Moist or dry soils; tolerates heavy soils. Drought tolerant when established. Tiny, paired, pink, bell-shaped flowers. Eventually forms a thicket. Controls erosion.

Tiaralla trifoliata (foam flower): Perennial. 8-14 inches tall x 1-14 inches wide. Shade to part shade. Spreads very slowly by rhizomes or seed. Needs moist, well-draining soil rich in organic matter. Panicles of white to pale pink flowers bloom from late spring to late summer. More details here.

Sedum spathulifolium with syrphid fly

 

Copyright 2015 Eileen M. Stark

To leave a comment, click on blog’s title