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April 4, 2003

Eastern Tent Caterpillar Collection Guidelines

By Bruce Webb
Department of Entomology
University of Kentucky College of Agriculture

As part of the response to Mare Reproductive Loss Syndrome (MRLS), the University of Kentucky in collaboration with the MRLS Response Team has established a unit to collect, store and distribute Eastern Tent Caterpillars (ETC) to qualified research teams investigating the syndrome. This activity is a volunteer service activity for the benefit of the industry and the MRLS research community. We will be collecting ETC larvae ourselves but will also accept donations of insect larvae from area farms that are interested in contributing. Here we provide some guidance for those that may wish to help with the research and so that collectors are aware of precautions that should be taken in collecting insect larvae.


Eastern Tent Caterpillars can cause mild to severe allergic reactions in humans. Therefore general precautions should be taken to prevent exposure to these materials. We advise:

Protective clothing and devices

Insect Frass (excrement)

The black pellets from tent caterpillar nests is insect excrement and leaf material. The insect excrement is also allergenic and should be avoided. There is no need to separate caterpillars from nest material and excrement or even small branches as this will be done before use of the material.


Eastern Tent Caterpillars are experimentally associated with Mare Reproductive Loss Syndrome. There is no experimental evidence that these insects cause abortions in other animals or other toxic effects beyond allergic reactions. However, it will do no harm to take precautions to minimize exposure.

Collection containers

We have used plastic boxes 16x10x6 inches in size with a plastic 'snap-on' lid. These can be purchased at many stores. If insects are delivered in other containers we will transfer them to these boxes for storage. When collecting we have filled this boxes about half full and found that most caterpillars survive well and few escape. Caterpillars can be stored in these containers up to 12 hours if they do not become too warm (e.g. left in hot car or in direct sunlight). If larvae must be stored longer than 12 hours they should be placed in a freezer and delivered frozen. This does not inactivate the material that causes equine abortions.

Delivery of donations

Three drop-off facilities will operate from April 15 to the end of May. Caterpillars can be delivered to:

  1. The University of Kentucky Entomology Department, the Webb laboratory, on the corner of Limestone and Cooper (Agricultural Sciences North Building Room S-226, Dr. Bruce Webb)
  2. The Livestock Disease and Diagnostic Laboratory, Newtown Pike
  3. The Maxwell H. Gluck Equine Research Center (Dr. Karen McDowell)

Collection sources

Although ETC are most common on cherry trees on horse farms they also attack many ornamental trees. We want insects from any host tree and it is often easier to collect the insects from smaller ornamental trees.

Identifiable collection sites by farm

We would prefer that the larvae be labeled with the specific farm or area from which they were collected. This is not required.

Time of collection

Tents and caterpillars in trees from April to May 15 will be ETC and can be collected. Later in the spring forest tent caterpillars build nests in some of the same trees. Forest tent caterpillars have not been associated with MRLS.


Care should be taken to collect larvae that have not been sprayed with insecticide.


Please do not climb trees to collect nests. Pruning saws on extensions can remove most accessible nests and some insects will simply be inaccessible.

Efficient collection

It is most efficient to collect ETC when they are aggregated in the nests. The nests can be removed manually or by clipping branches that contain the nests and placing the entire nest in the collection container.


As with any activity in the environment there are some risks that are associated with collecting insect larvae.
These include:

  1. Falling
  2. Allergic reactions
  3. Unrecognized toxins and toxic reactions


If you elect to collect specimens, your activity is strictly voluntary, at your own risk, and no compensation or benefits of any type is offered. We will gratefully accept such donations and use them to advance cooperative investigation of this syndrome.

Additional note

Dr Lynne Rieske-Kinney and her student Beth Choate, are monitoring field sites for caterpillar development and mortality. Beth has a number of sites with natural and supplemented tents located along the Bluegrass Parkway on the north and south sides of the road, between mile markers 71 and 67. It is imperative that Beth's field sites remain undisturbed.

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