Rhinoceros Beetles, Subfamily Dynastinae

Members of the beetle subfamily Dynastinae include some impressive-looking beetles with impressive-sounding names: rhinoceros beetles, elephant beetles, and Hercules beetles. The group includes some of the largest extant insects on Earth, many with impressive horns. For purposes of this article, we will use the term rhinoceros beetles to represent all members of this subfamily.

Description

Rhinoceros beetles and other members of the subfamily Dynastinae are usually convex and rounded in shape (similar to lady beetles in shape, but much larger). The species that inhabit North America aren’t as large as those found in other parts of the world, but our eastern Hercules beetles (Dynastes tityus) reach a still-impressive 2.5 inches long.

Identification of this subfamily requires some knowledge of beetle morphology and its associated terminology. In rhinoceros beetles, the labrum (upper lip) is hidden beneath a rounded, shield-like structure called the clypeus. Rhinoceros beetle antennae consist of 9-10 segments, usually with the last 3 segments forming a small club. For additional identifying traits of this subfamily, please refer to the details provided on the Generic Guide to the New World Scarab Beetles website.

Classification

• Kingdom – Animalia
• Phylum – Arthropoda
• Class – Insecta
• Order – Coleoptera
• Family - Scarabaeidae
• Subfamily - Dynastinae

Diet

Rhinoceros beetles and other members of the subfamily Dynastinae generally feed on decomposing vegetation (rotting wood, leaf litter, etc.) as larvae. Many adults feed on decaying plant roots underground, although some species also appear to feed on sap and fermenting fruit.

Life Cycle

Like all beetles, rhinoceros beetles undergo complete metamorphosis with four life stages: egg, larva, pupa, and adult. Some species are relatively long-lived as insects go, and may take up to two years to reach maturity.

Special Adaptations and Defenses

Male rhinoceros beetles often bear large horns, either on the head or the pronotum, which they use to joust with other males in battles over territory. Remarkably, recent research showed these enormous and bulky horns don’t impede the male rhinoceros beetle’s ability to fly.

Range and Distribution

Rhinoceros beetles and their kin live throughout the world, with the exception of the polar regions, and are most diverse in the tropics. Scientists have described approximately 1,500 species to date and subdivided these into eight tribes within the subfamily Dynastinae.

Sources

• Beutel, Rolf G., and Richard A. B. Leschen. Volume 1: Morphology and Systematics (archostemata, Adephaga, Myxophaga, Polyphaga Partim). 
• Dynastinae, Generic Guide to New World Scarab Beetles, University of Nebraska State Museum.
• Eaton, Eric R, and Kenn Kaufman. Kaufman Field Guide to Insects of North America.
• Harpootlian, Phillip. "Subfamily Dynastinae - Rhinoceros Beetles", BugGuide.Net, March 2005.
• McCullough, Erin L., and Bret W. Tobalske. “Elaborate Horns in a Giant Rhinoceros Beetle Incur Negligible Aerodynamic Costs.” Proceedings of the Royal Society B: Biological Sciences, vol. 280, no. 1758, The Royal Society, May 2013, p. 20130197.
• Triplehorn, Charles A, and Norman F. Johnson. Borror and Delong's Introduction to the Study of Insects. 7th edition.