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Monday, July 23, 2018

Nicole’s bug of the week – The White Lined Sphinx Moth

Nicole’s bug of the week – The White Lined Sphinx Moth
This week’s Bug of the Week is one that we were getting reports and questions about from the Tulia area this year but are actually an annual curiosity for all but usually after causing some panic for gardeners and producers.  The white-lined sphinx moth, also known as the hummingbird or hawk moth. Sphinx moths are found throughout North America but many more are native to tropical climes. There are over a thousand types of sphinx moth worldwide and 125 in North America alone. The moth gets its name from its caterpillar, which will rise into a “sphinxlike” pose if disturbed. These caterpillars can and do grow to be quite large, up to four inches long, which is pretty impressive, but the adult moths might be even more so.  Some species of adult sph6inx moths can have a wingspan of up to eight inches while the white lined sphinx moth, our native sphinx, has a wingspan of about 3-4 inches.  These moths are so humming bird like, they are even sometimes mistaken for humming birds.

The caterpillars of the white lined sphinx are a type of hornworm so called for the small horns the sprout from their rear ends, which are impressive in their own right.  Don’t worry, those horns on our local worms are not too hard or poisonous but caution is strongly suggested as many horned insects do pack a poisonous horn or bristle of some sort.  Coloration of the white lined sphinx caterpillar varies some, but caterpillars are typically a vibrant green with bold yellow, black, and white stripes running down their sides.

The sphinx’s life cycle is fairly typical for a moth. In spring or summer, the female of the species will lay as many as one thousand eggs on the plants that the larva will eat. In 2 to 3 days, the eggs hatch into caterpillars and begin to feed. In about eight weeks the caterpillar will be full grown and will burrow underground. If the region has a sufficiently cold winter, much like the Texas High Plains, the caterpillar will overwinter underground limiting the local population to one generation per year.  In the spring they will emerge as an adult sphinx moth typically to fly at sunrise and sunset, drink the nectar of flowers, and reproduce until winter. 

In many years the annual arrival of the caterpillars causes quite a stir, most recently in 2014 where there were an abnormally large amount moving across fields, farms, and pastures from Kansas to Lamesa.  The larva tends to hatch about the same time and move across the countryside in vast numbers, sometimes numbering in the millions.  This can be quite stressful to watch as they move across cotton, sorghum, or vegetables.  As of this date, they have never caused any economic problems as they are very picky eaters.  The larva only feast on purslane weeds locally, almost completely ignoring other plants and healthy foliage nearby.  Their listed diet can consist of variety of plants which include portulaca, primrose, wild grapes, and a few types of succulent trees.

Borror, Donald J., Triplehorn, Charles A., Jonson, Norman F. “An Introduction to the Study of Insects.” Sanders College Publishing, 1989, pg. 652-653

Metcalf, C. L., Flint W. P. “Destructive and Useful Insects.” Theirs Habits and Control, R. L. Metcalf, McGraw Hill Book Company, 1962, pg. 258

Borror, Donald J., White, Richard E. “Insects.” Peterson Field Guides, R. T. Peterson, Houghton Mifflin Company, 1970, pg. 642

Reed, B. Porter, P. Bynum, E., 2014. July 1, 2014, Plains Pest Management Newsletter, The Sudden Appearance of Large Horned Caterpillars Cause Concerns.

Thanks Nicole,

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