Sunday, October 5, 2014

Spiny Oak Slug

While I was volunteering at the "Bear Aware" table at MDC's Great Outdoor Days at Bois D'arc CA, a young naturalist named Timothy brought up this caterpillar, one of several like it he had found.  He has been hunting for caterpillars "for a long time" and raises them at home to adulthood.  This degree of sophistication at his age is quite impressive.

His find is a spiny oak slug caterpillar, Euclea delphinii, a colorful creature which comes in a remarkable variety of different colors.  Bright colors are frequently a warning to predators that "I taste bad" or "I can hurt you".  In the case of E. delphinii, it is the latter as those hairy spikes have a fluid that can cause a stinging sensation.

Another color -  Kevin Firth
While many larvae of lepidoptera eat only a limited species of plants, the oak slug relatively omniverous.  It eats " a variety of deciduous trees and shrubs, not limited to: apple, ash, basswood, beech, birch, blueberry, cherry, chestnut, hackberry, hickory, maple, oak, poplar, sycamore and willow," (Wagner, 2005*).

...and another color,  - Jon Rapp
and another! - Bob Barber
There are a number of different species of "stinging caterpillars".  The buck moth and the colorful io silkworm moths have this feature as well as the saddleback caterpillar and the hag moth, coming soon to the blog.  They have in common specialized hairs.
"Stinging caterpillars possess hollow quill-like hairs, connected to poison sacs, that are used as defensive weapons. When these hairs are touched they break through the skin releasing the poison. Reactions can range from a mild itching to the more severe pain, dermatitis, and even intestinal disturbances."  University of Kentucky
Slug moth caterpillars have a unique way of traveling with a wave-like motion,  They can leave a sticky trail not unlike a slug.  This is produced by the suction cups on its eight abdominal segments, replacing the usual prolegs of other caterpillars.

While finding the caterpillars requires diligent searching skills like Timothy's, the cute little (10 mm) moth can be found occasionally on the siding by our deck light.  Once mated, the females lay their eggs on leaves, and generally produce two generations of offspring a year from Missouri on south.

*  If you are interested in caterpillars, Wagner's Caterpillars of Eastern North America is a good place to start.

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