The newest study on early fetal loss and Eastern tent caterpillars began on May 21 and will continue for the next three weeks. The research is funded by the Grayson-Jockey Club Research Foundation and headed by internal medicine specialist Bill Bernard, DVM, Dipl. ACVIM, president of the Kentucky Association of Equine Practitioners, and reproductive specialist Michelle LeBlanc, DVM, Dipl. ACT, both of Rood and Riddle Equine Hospital in Lexington, Ky. (see Article Quick Find #3591 At www.TheHorse.com).

In researching more information about Eastern tent caterpillars, we again turned to Terry Fitzgerald, PhD, a distinguished university professor of biological sciences at the State University of New York College at Cortland. Fitzgerald, who literally wrote book on the Eastern tent caterpillar, said he had spoken to LeBlanc about the Kentucky study. Fitzgerald said he thought it was important to use the last instar (last phase of the larval or caterpillar stage), which is what the researchers are using. The last instar caterpillars are the ones who leave the trees and wander across the fields in search of a place to spin a cocoon.

Caterpillars have five “molts” while in the nest. A molt is like a snake shedding its skin. The Eastern tent caterpillar sheds it’s external cuticle (exuviae) and leaves pieces in the tent. There are about 300 caterpillars in each tent, so with five molts that means 1,500 exuviae or fragments thereof. It is possible that these fragments of the shed cuticle of the caterpillar might play a part in the mare reproductive loss syndrome (MRLS) since nests that have frass (excrement) used in the studies also have exuviae, including hairs.

It is known that the setae or hairs of caterpillars, including the Eastern tent caterpillar, can cause irritation to other animals. The harmful effects of moths or butterflies (or their larvae) on people is called lepidopterism. (The term “erucism” refers to the deleterious effects of the caterpillars on humans). Fitzgerald said there are about 150 types of caterpillars worldwide with irritating hairs, and that the Eastern tent caterpillar’s hairs are usually not particularly irritating