This month’s “bug” comes by way of MG Jeff Goggin. He stopped by the house to show me pictures of caterpillars on a Milkweed plant (see Jeff’s photo below left). The photos were of the Milkweed Tussock caterpillar.
This caterpillar is recognized by its very hairy appearance, with numerous black, orange or yellow and white tufts and lashes. Thick black lashes extend from ends of its body and sides of the anterior abdominal segments. There are long white lashes extended from the sides and top at each end, and orange tussocks that curve upward over the top of the segments.
Their geographic range is from Minnesota to Maine, up to Quebec and Ontario, and south to Florida (map of primary ranges is shown below). They are also sporadically found in Texas and the southwest.
The size of the caterpillar larva is up to 3.5cm (2.5cm = 1 inch) and it feeds on Milkweed, also Dogbane. See photo below from Michigan State University of newly hatched Milkweed Tussock larvae feeding. Adult moths have a wing span of 32-43mm (25mm = 1 inch). The wings are usually gray and unmarked. Their abdomen is yellow with black spots. At times, adults may be found on the host plant during the day.
Females lay their eggs in “rafts” and, upon hatching, the young caterpillars are gregarious, and tend to stay in a group, until the third instar; they become solitary in later instar stages. They often defoliate individual plants in gardens and nurseries and, in some years, may erupt into numbers that may defoliate entire patches of Milkweed. There is concern that this may cause competition with the Monarchs and, therefore, affect the Monarch’s food supply.
Researchers have found Monarchs appear to prefer young, vigorous growth of the plant versus the Milkweed Tussock which seems to be content with the older foliage, even those that are yellowing. The pupa overwinters in a cocoon. Caterpillars are found starting in June, and adults are usually seen during May to September in much of their range. Generally, there are two generations per year except in Canada. Other common names are Milkweed Tiger Moth, Milkweed Tussock Caterpillar (larva stage), and Harlequin Caterpillar (larva stage).
- Bugguide.net, dan40165, Bullitt Co., KY, 07/31/2017: https://bugguide.net/node/view/1417529
- Euchaetes egle US Map, MS Entomological Museum at Mississippi State University: http://mothphotographersgroup.msstate.edu/map/cache/overall/map_8238.jpg
- Milkweed Tussock larvae feeding, Michigan State University: http://msue.anr.msu.edu/uploads/images/mw19_1.jpg
Research References / Resources:
- National Wildlife Federation’s Field Guide to Insects and Spiders of North America, by Arthur V. Evans
- Princeton Field Guide’s Caterpillars of Eastern North America, by David L. Wagner
- BugGuide.net, species Euchaetes egle – Milkweed Tussock Moth
Author: Jim Revell, Bedford Extension Master Gardener
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Get to know your insect neighbors! As always, feel free to contact your local Extension Master Gardeners with questions or concerns you may have about insects in your area.