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Wildlife Wonders

Today is Sphinx Moth Day!

Sphinx or Hawk Moths are in the family Sphingidae and within the order Lepidoptera that includes both butterflies and moths.  
Of the estimated population of 11,000 moths in the United States, the east has about 70 species of sphinx moths.  Worldwide there are greater than 1,500 species of sphinx or hawk moths and “comprise one of the most conspicuous and well-studied groups of insects”.  Some research indicates hawk moths possess acute color vision for discriminating the color of flowers and their scales have evolved to jam bat sonar.  In the seasonally dry forests of the tropics nearly 10% of the trees may be pollinated by the Sphingidaes.  

The caterpillars are large and usually possess a horn, eyespot or hardened button.  They have prolegs that aid in climbing and are flattened with small hooks, crochets, for grasping leaves and twigs.  Our largest hawk moth caterpillar is the Giant Sphinx that may exceed 6 inches in length.  
These amazing animals, the sphinx moths have long narrow wings and short stout bodies.  They move their wings incredibly fast and are strong, acrobatic fliers.  Much like a hummingbird many species can hover in place and briefly fly backwards or side to side.  Most of the adults have a very long tongue or proboscis, straw-like tube, capable of probing deep into flowers for nectar.  The giant hawk moth, endemic to Madagascar, has a nearly 12 inch long proboscis. It was discovered in 1882, but 20 years earlier Charles Darwin had made a prediction that there must be a moth that had co-evolved with the Star-of-Bethlehem orchid. This orchid had a foot-long nectar spur and the nectar was only pooled at the bottom.  He was correct and Darwin’s theory of coevolution, the development of two species is driven or modified by the other, was confirmed.  
While sitting outside in the late afternoon, attempting to video a ruby-throated hummingbird that was visiting our purple salvia, I was rewarded with the site of a nessus sphinx moth drinking nectar from the leucothoe and rhododendron bushes.  I had seen the hummingbird clearwing moth previously, but had not remembered seeing this easily recognizable sphinx moth.  It clearly had two light-colored bands on its abdomen.  
The hummingbird moth flies and moves like the hummingbird and even emits an audible hum like a hummingbird.  Most sphinx moths fly at night, hummingbird and nessus sphinx moths fly during the day. Their wings beat so fast they are nearly invisible.  

Large, smooth spherical eggs are laid on the underside of a leaf.   Young caterpillars feed on the leaf and will move violently from side to side when disturbed and will even regurgitate a sticky green fluid.  Some caterpillars will nip at their predator and some actually make a sound when harassed.   Most overwinter underground as a pupae.  They are given the name “sphinx” moth for the resemblance of the larva to the Egyptian Sphinx, since they often rest with the thorax raised in the air and the head pointed downward.  Called “hornworm” because they have a stiff, pointed “horn” at the end of the abdomen.

Although some species, like the tomato and tobacco hornworm, have been maligned due to their feeding habits.  In addition to eating the leaves it also consumes the green fruits, flowers and terminal shoots.  Caterpillars are attacked by the braconid wasp that lays its eggs in the caterpillar, the cocoons of the wasp look like grains of rice on each larva.  The caterpillars are doomed if attacked by these wasps.   Many sphinx moth species are beneficial since they pollinate flowers when sucking nectar. Scientific research of how these insects stay airborne while hovering is of special interest in the design of small flying robots.

Resources
Caterpillar Anatomyhttps://www.enchantedlearning.com/subjects/butterfly/anatomy/Caterpillar.shtml
US Forest Service – Hawk Moths or Sphinx Mothshttps://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/hawk_moths.shtml
Missouri Department of ConservationSphinx Moths (Hawk Moths)
Sphinx Moths (Hawk Moths)Sphinx moths are usually large and heavy bodied, with a long, pointed abdomen. Members of this family often hove…

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