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Saturday, September 16, 2017

It's a Sphinx, Methinks!

A White-lined Sphinx hovers while feeding at a thistle
A family of moths called the Sphingidae are more commonly known as hawk moths, hummingbird moths, and sphinx moths.  This family has over 1,450 species worldwide, and 73 of them are known to be present in Texas.  Generally speaking, these moths are named not just for their streamlined bullet-shaped bodies that have long narrow forewings and short hindwings, but also for their distinct behavior which comes in the form of swift, hovering flight.  Many species in this family hover in mid-air or swing from side to side when feeding on flowers, an ability that has evolved in only three other groups: hummingbirds, certain bats, and hoverflies.  In addition to nectaring on flowers, these moths often pollinate them at the same time.  

The leaf-feeding caterpillars or larva of these moths typically have a smooth body with a characteristic horn near their posterior end, hence the common name hornworm.  They pupate in an earthen cell or loose cocoon at or near the soil surface.  The word sphinx was first associated with the larva in 1736, when Rene Reaumur, a French scientist and entomologist, noted that they often assumed a pose reminiscent of the mysterious Egyptian Sphinx of antiquity.  They accomplish this pose by holding their anterior legs off their substrate and tucking their heads underneath when resting, which appears to form an upright praying position.  

Vine Sphinx

White-lined Sphinx
In our area, some of the more interesting sphinx moths include the Vine Sphinx (Eumorpha vitis), Tersa Sphinx (Xylophanes tersa), Waved Sphinx (Ceratomia undulosa), and Rustic Sphinx (Manduca rustica).  The Vine Sphinx appears similar to the well-known White-lined Sphinx, but is dark greenish-brown with a more complex pattern of sharp whitish streaks and bands on its forewings (instead of an even, pale tan stripe from base to tip intersecting uniform white lines) and a small pinkish patch on its hindwings (instead of a broad pink band).  The wingspan of this moth is 3.5 to 4 inches, it flies from April to May and July to October, and the larva feed on grapevines.  

Tersa Sphinx
The Tersa Sphinx is easily identified by its long pointed abdomen, brownish-tan forewings that look like woodgrain, and hindwings with jagged black and white markings.  This sleek, fighter jet-like moth has a wingspan of 2.5 to 3 inches, flies June to October, and its larva feed on catalpa and smooth false buttonweed.

Waved Sphinx
The Waved Sphinx has brownish-gray forewings with contrasting black streaks and zigzag lines and a small, kidney-shaped white spot outlined in black, while the hindwings are gray with darker gray shading.  Its wingspan is 3 to 4.5 inches, it flies from May to October, and its larva feed on ashes and oaks.  

Rustic Sphinx

The Rustic Sphinx has an abdomen with three pairs of yellow spots along the sides, and yellowish to chocolate-brown forewings with black zigzag lines. It has a wingspan of 3.5 to 6 inches, flies from July to October, and its larva feed on crossvine and trumpet vine. 

Certain species of sphinx moths have been widely used in scientific research aimed at better understanding animal flight and insect physiology.  Some have played a key role in advancing knowledge of hormones produced by nerve cells, while others have contributed to the development of small flying robots by shedding light on how these insects stay airborne while hovering.  Those are some pretty important roles for a sphinx, methinks!