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Publication #EENY-052

Regal Moth, Citheronia regalis (Fabricius)1

Donald W. Hall2

Introduction

The regal or royal walnut moth is one of our largest and most spectacular moths. Like most other moths, it is nocturnal but is sometimes observed at lights. The imposing larva, known as the hickory horned devil, is most often observed when it is full grown and comes down from the trees to wander in search of a site for pupation.

Distribution

The regal moth is found throughout the deciduous forest areas of the eastern U.S. from Missouri to Massachusetts and southward to Texas and central Florida. It is more common in the southern part of its distribution.

Description

Adult: The regal moth has a wingspan of 9.5-15.5 cm. Females are larger than males. The forewings are gray to gray-green with orange veins and a row of seven to nine yellow spots near the distal margin. There also are single yellow discal and basal spots. The hind wing is mostly orange with a basal yellow spot and yellow patches (or spots) on the costal and anal margins. The hind wing may also have one to two rows of gray-green spots. The body is orange with narrow yellow banding.

Figure 1. 

Regal moth, Citheronia regalis (Fabricius).

Larva: The hickory horned devil is among the largest of our native saturniid caterpillars (12.5-14 cm in length - about the size of a large hot dog) They vary slightly in color, but are commonly blue-green. The second and third thoracic segments each bear two long and two shorter orange, black-tipped scoli. Abdominal segments each have four short, black scoli, and segments 2 to 8 have a pale, oblique lateral stripe. Although the larva has a fierce appearance, it is harmless.

Figure 2. 

Full grown hickory horned devil caterpillar, regal moth, Citheronia regalis (Fabricius).

Life Cycle

The regal moth typically has only a single generation per year, although a few late collection records suggest the possibility of a small second brood in the deep south. In Florida adults have been collected in May, but are more common during the summer. Adults have vestigial mouthparts. Adults mate during the second evening after emergence and begin oviposition at dusk of the third evening. Eggs hatch in six to 10 days, and the duration of the larval stage is about 35 days.

Larvae have been reported from a variety of host tree species. They are commonly found on species of the family (Juglandaceae) including walnut (Juglans nigra), butternut or white walnut (Juglans cinerea), and a variety of hickories (Carya spp.) including pecan. In Florida, larvae are frequently found on sweetgum (Liquidambar styraciflua). Other hosts commonly listed are persimmon (Diospyros virginiana) and sumacs (Rhus spp.). In central Florida, larvae are usually found from late July to mid-August while they are wandering on the ground searching for a suitable location to burrow into the soil for pupation. The pupa is the overwintering stage.

The regal moth is a beautiful and fascinating member of our native fauna, and its larvae should not be killed. If a larva is found crawling on pavement or in an area of thick turf grass where it would have difficulty burrowing, it should be moved to an area of soft soil or a mulched area where it can burrow for pupation.

Selected References

Arnett, R.H., Jr. 1985. American Insects. Van Nostrand Reinold Company, Inc. New York. p. 587.

Covell, C.V. 1984. A Field Guide to the Moths of Eastern North America. Houghton Mifflin Company. Boston, MA. p. 45-46.

Ferguson, D.C. 1971. The Moths of North America. E.W. Classey Ltd. Middlesex, England. p. 32-33.

Kimball, C.P. 1965. Lepidoptera of Florida. Arthropods of Florida, Vol. 1. Division of Plant Industry, State of Florida Department of Agriculture. Gainesville, FL. p. 70.

Medley, J.C., and T.R. Fasulo. (1998). Florida Butterfly Tutorials. http://pests.ifas.ufl.edu/software/det_bfly.htm. (September 1998).

Stehr, F.W. 1987. Immature Insects. Vol. 1. Kendall/Hunt Publishing Company. Dubuque, IA. p. 515.

Worth, C.B., A.P. Platt, and T.F. Williams. 1982. Differential growth and utilization of three foodplants by first instar larvae of Citheronia regalis (Saturniidae). J. Lepid. Soc. 36: 76-82.

Footnotes

1.

This document is EENY-052, one of a series of the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date August 1998. Reviewed March 2008. This document is also available as a Featured Creature at http://entomology.ifas.ufl.edu/creatures. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

2.

Donald W. Hall, professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.