Tag Archives: Charles Darwin

MINIATURE HUMMINGBIRD, ENORMOUS FURRY BEE, FLYING LOBSTER, OR MUTANT NEW WORLD CREATURE?

Hummingbird and Snowberry Clearwing Moths

By Kim Smith

Startled! is an apt description of the reaction most gardeners experience when first they encounter a clearwing moth. Hovering while nectaring, with wings whirring rapidly and audibly, is it a miniature hummingbird, enormous furry bee, flying lobster, or mutant new world creature?Verbena and Hummingbird Clearwing MothHummingbird Clearwing Moth  (Hemaris thysbe) nectaring at Verbena bonariensis 

The family Sphingidae are easily identified in both their adult and caterpillar forms. The medium-to-large-sized sphinx, or hawk, moths have characteristic robust, chunky bodies tapering to a point, and slender wings, which are adapted for rapid and sustained flight. Often mistaken for hummingbirds, the Hummingbird Clearwing Moth (Hemaris thysbe), with green tufted body and ruby colored scales, suggesting the male hummingbird, and the Snowberry Clearwing Moth (Hemaris diffinis), with the gold and black striped color pattern similar to that of a fat bumble bee, mimic both the bees and birds they fly with during the day. The ability of certain Sphingids to hover in mid air while nectaring is unusual in nectar feeders and has evolved in only three species: Sphingids, bats, and hummingbirds. Sphinx moths also do an exceptionally unusual movement called “swing-hovering,” swinging from side to side while hovering, it is thought, in an effort to escape predators lying in wait amongst the flora.

Snowberry Clearwing Moth (Hemaris diffinis), nectaring at Buddleia

Sphinx moths are grouped together because their caterpillars hold their head and thorax erect in a sphinx-like fashion. Most larvae have a horn protruding from their last segment. For this reason, they are often called hornworms. The adult sphinx moth is a powerful flier and usually has a long proboscis suitable for tubular-shaped flowers with a deep calyx, such as trumpet vine. The slender wings must beat rapidly to support their heavy bodies. The names of many sphinx or hawk moth species correlate to their caterpillar host plant, to name but a few examples: Catalpa Sphinx, Huckleberry Sphinx, Paw Paw Sphinx, Cherry Sphinx, and Elm Sphinx.

The order Lepidoptera is comprised of butterflies, moths and skippers. The name is derived from the Greek lepidos for scales and ptera for wings. Their scaled wings distinguish them as a group from all other insects. Shortly after the Hummingbird and Snowberry Clearwings are born, they immediately begin to shed their wing scales, hence the common name clearwing moth. While nectaring, moths receive a dusting of pollen as they brush against the pollen-bearing anthers. Their fuzzy, fur-like scale-covered bodies are an excellent transporter of pollen. Because moths are on the wing primarily at night, moth-pollinated flowers are often white and pale, pastel-hued and tend to be sweetly scented. White flowers are more easily distinguished in the evening light, whereas colorful flowers disappear. Adult clearwing moths are diurnal (day flying) and nectar at a variety of flowers. In our garden, they are most often spotted at our native Phlox ‘David,’ bee balm (Monarda didyma), purple-top Verbena bonariensis, and butterfly bushes with blue and white flowers. The larvae of Hummingbird Clearwings feed primarily on viburnum, honeysuckle, and snowberry (all Caprifoliaceae), and less commonly on hawthorn, cherry, and plum (Rosaceae). Snowberry larvae feed on honeysuckle and snowberry.

Hummingbird Clearwing Moth nectaring at native Phlox paniculata ‘David’
(Click photo to see full size image)

For the most part, Sphinx moths are on the wing at night, although the beautiful White-lined Sphinx (Hyles lineata) is often seen at dusk. The forward wings are dark olive brown streaked with white. The hind wings are black with a vivid band of rose-pink. Found throughout North America, both larvae and adults are consummate generalists. The caterpillars feed on the foliage of apple trees, four-o’clocks, evening primrose, elm, grape, and tomato. The adults nectar at a wide variety of flowers including larkspur, gaura, columbine, petunia, moonflower, lilac, bouncing bet, clover, Jimson weed, and thistle. White-lined Sphinxes are drawn to lights and those that remain in the garden the next morning are quite subdued, and may come to your finger.

Snowberry Clearwing

Orchids often have a symbiotic relation to very specific sphinx moths. The starry white, six-petalled Comet Orchid (the French common name, “Etoile de Madagascar” means “Star of Madagascar”) produces nectar at the bottom of an extremely long corolla, nearly a foot in length. Star of Madagascar (Angraecum sesquipedale) was predicted by Charles Darwin to have a highly specialized moth pollinator with a proboscis at least that long.  “Angraecum sesquipedale has nectaries eleven and a half inches long, with only the lower half filled with very sweet nectar…it is, however, surprising, that any insect should be able to reach the nectar: our English sphinxes have probosces as long as their bodies; but in Madagascar there must be moths with probosces capable of extension to a length of between ten and twelve inches!” (Darwin). The giant hawk moth Xanthopan morganii praedicta (“the predicted one”) was named appropriately upon its discovery, after Darwin’s death.

Etoile de Madagascar and Hawk Moth Xanthopan morganii praedicta

Image courtesy wiki commons media

Co-evolution, the specialized biological embrace of two species, bears both benefits and risks. Each partner benefits in that no energy is wasted on finding ways to reproduce. The risk lies in becoming too dependent on a single species. If one half of the co-evolved partnership perishes, the other will surely become extinct as well.

This article was first published on August 3, 2011 and was subsequently republished by the New England Wildflower Society.

 

What is Adaptive Radiation?

One of the most striking evolutionary patterns observed is called adaptive radiation. To radiate means to spread outward; not in the sense of speading out physically, but referring to a species that diversifies (“spreads out”) and generates multiple daughter species.

From Biology Online: When Charles Darwin was in the Galapagos islands, one of the first things he noticed is the variety of finches that existed on each of the islands. All in all, there were many different species of finch that differed in beak shape and overall size. This is adaptive radiation and natural selection at work.

Darwin’s Finches

These finches, better known as ‘Darwin’s Finches’ illustrated adaptive radiation. This is where species all deriving from a common ancestor have over time successfully adapted to their environment via natural selection.

Previously, the finches occupied the South American mainland, but somehow managed to occupy the Galapagos islands, over 600 miles away. They occupied an ecological niche with little competition.

As the population began to flourish in these advantageous conditions, intraspecific competition became a factor, and resources on the islands were squeezed and could not sustain the population of the finches for long.

Due to the mechanisms of natural selection, and changes in the gene pool, the finches became more adapted to the environment, illustrated by the diagram below.

Adaptive Radiation in Darwin's Finches

As competition grew, the finches managed to find new ecological niches, that would present less competition and allow them, and their genome to be continued.

As indicated by the diagram above, the finches adapted to take advantage of the various food sources available on the island, which were being used by other species. Over the long term, the original finch species may have disappeared, but by diversifying, would stand a better chance of survival.

All in all, the finches had adapted to their environment via natural selection, which in turn, has allowed the species to survive in the longer term, the prime directive of any species.

See related post Silversword Alliance.

Follow this link to read more about rapid adaptive radiation in the species rich Heliconius butterflies (longwings or passion-flower butterflies).

Heliconius butterflies

Director’s Series at the Arnold Arboretum

Tulip Tree (Lirodendron tulipfera) American native tulip tree on the front lawn of the Hunnewell Building at the Arnold Arboretum

A Darwinian Look at Darwin’s Evolutionist Ancestors

Last night I had the pleasure of hearing Ned Friedman, the new Director at the Arnold Arboretum, speak about the early history of evolutuonary thought. Well-spoken, passionate, and comprehensive in his presentaion, Friedman answers the question “Is Darwin truly deserving of his place in history?” Although approximately fifty naturalists, horticulturalists, arborists, theologians, philosophers, poets, and medical practitoners had advanced evolutionary concepts for the diversification of life, it was Darwin who wrote about and developed the concept most exhaustively and comprehensively (most notably, On the Origins of Species, 1859) and conclusively, and it was Darwin who convinced the rest of the scientific world. Interestingly, we learn that Charles Darwin’s grandfather, the physician and naturalist Erasmus Darwin (a great friend of our forefather Benjamin Franklin– are you listening tea party creationists?) most certainly planted the seed and devolped the foundation for his grandson’s theories on evolution, through his own writing Zoonomia (or the Laws of Organic Life, 1794).

Erasmus Darwin writes “Would it be too bold to imagine, that in the great length of time, since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind, would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which THE GREAT FIRST CAUSE endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions, and associations; and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down those improvements by generation to its posterity, world without end!”

It is not easy leaving my cozy home on a frigid New England evenning. I usually have to depart a full two to two and half hours prior to any event in the city when it is scheduled anywhere near rush hour. This makes for a very long evening, however, I find all the progams that the Arnold Arboretum has to offer entirely worth my while and last night’s presentaion was no exception. I am very much looking forward to the upcoming lecture topic Restoring Hawaii’s Marvels of Evolution, presented by Robert Robichaux, scheduled for Monday, February 7 at 6:30.

All programs in the Directors Lecture series are free but you must register ahead of time online or call 617.384.5277.

Tulip tree (Lirodendron tulipfera). Lirodendron is a genus of only two species of trees in the Magnoliaceae; both are known under the common name tulip tree. Lirodendron tulipfera is native to eastern North America, while Lirodendron chinese is native to China and Vietnam.