Biodiversity Highlight - Series #3: Scarabaeidae of the Bull Run Mountains - Part One
Biodiversity Highlight (Series #3: Part One): Dynastes tityus (Eastern Hercules Beetle)
Virginia Outdoors Foundation - Bull Run Mountains Natural Area Preserve
Eastern Hercules Beetle (Dynastes tityus) ♂ - An adult specimen observed in the Northern Section of The Preserve
© Jacob Saucier (@saucierj), all rights reserved (used with permission)
Hello again everyone,
Welcome to the third installment of our biodiversity highlight series, in which we review some of the amazing biodiversity held within the natural sanctuary of the Bull Run Mountains Natural Area Preserve. This week we will be diving into one of the largest Coleopteran families - the Scarabaeidae, or scarab beetles. It's likely everyone has heard of and had interactions with this varied family of beetles, which includes the likes of dung beetles (Scarabaeinae), flower chafers (Cetoniinae), and Rhinoceros beetles (Dynastinae). The family itself is massive in comparison to our last highlighted families, with the Scarabs including some 30,000 species worldwide and approximately 1,400 species north of Mexico. In an attempt to keep this series manageable, it will highlight some of the more commonly observed and particularly interesting species of scarabs that have been observed on The Preserve.
With this in mind, let's jump in with one of the most notable members of the family in our area, the Eastern Hercules Beetle, Dynastes tityus,. The Eastern Hercules Beetle is especially charismatic and is even featured on the seal of the American Entomological Society. In a similar fashion to our previous highlighted species, this species is another great example of a gateway insect - having been an insect of inspiration for many aspiring entomologists, young and old, amateur and professional. With its large size, beautifully black-mottled greenish-tannish elytra, and impressive male horn - its noted charisma is self-explanatory. This species is one the largest species of beetle found in the United States, reaching lengths of between 40–60mm (1.6–2.4 inches) as an adult. It can be found throughout the Southeastern and Central United States inhabiting hardwood, and deciduous forests. Its formal range stretches from Maryland to Missouri, south to Texas and Florida. Per the course in this review of the "big beetles" of The Preserve, it is a saproxylic species, developing in and reliant on the abundant decaying woody materials across Bull Run. Despite white grubs being the bane of many gardeners, the species is harmless, both commercially and to handle.
The Eastern Hercules beetle goes by a handful of colloquial names including the rhinoceros beetle, elephant beetle, and even ox beetle. While descriptive of the species' likeness to large tusked, or horned animals, these are also the names of other Dynastine beetles. These include beetles like the Eastern rhinoceros beetle, Xyloryctes jamaicensis, which will be highlighted in an upcoming post. The scientific name Dynastes tityus is a great example of just how classically educated authors like Linneaus were when first describing the species in the 18th century. Linneaus, who assigned the name Scarabaeus tityus in 1763 in his work Centuria Insectorum, chose the specific epithet "tityus". The name doesn't directly translate from a classical Greek or Latin root word. Instead, the name "tityus" comes from the name of the mythological giant Tityos. A roundabout, but fitting name for our local giant.
Eastern Hercules Beetle (Dynastes tityus) ♀ - An adult female specimen observed in West Virginia
© Stephen ( @stephen_wv ), some rights reserved (CC-BY-NC-ND)
In our last highlights, finer taxonomic classifications like subfamilies and tribes weren't very important due to the relatively small number of species in each family present on The Preserve. For this series' feature family, we will need to discuss those finer taxonomic subunits to better classify and differentiate our highlight subjects as the series develops. Our champion of the Scarabaeidae this week, the eastern Hercules beetle, belongs to the subfamily Dynastinae, or rhinoceros beetles (easy to remember). Altogether, the Scarabaeidae includes about 8 subfamilies (depending on your taxonomic reference) in North America. These subfamilies include the Aphodiinae (small dung beetles), Scarabaeinae, Melolonthinae (June beetles), Oncerinae (a new subfamily on the block), Podolasiinae (new subfamily #2), Rutelinae (shining leaf chafers), Cetoniinae, and our Dynastinae. Not all of these subfamilies have been observed in the Bull Run Mountains (so we won't be covering all of them), but how we classify species is important - even if it is just to help us stay organized. We won't be arguing species theories here, but suffice it to say, taxonomy and our understanding of the diversity and classification of species is a very fluid system.
Knowing how to classify a species is important, but it's even more important to know how that species interacts with its environment. The ecology of the Eastern Hercules beetle is very similar to our previously reviewed Lucanidae and Passalidae highlights. The life cycle of this large species takes several years to complete, with most of its development being spent underground and feeding on decaying wood. Upon emerging, our forest giants only spend, at most, a couple of months taking in the sun and stars in search of a mate or suitable locations in which to oviposit the next generation. During this time, the males of this species may be found in serendipitous pitched combat among the branches of trees. Although Hercules beetles can be found among mix-hardwood forests across the Eastern United States, the species seems to have an intimate relationship with both Quercus spp. (our familiar oak - for reproduction and larvae development) and Fraxinus spp (ash trees - for courtship). While the species is now a rare sight, historically, observations of the Eastern Hercules beetles could be considered a nuisance due to the odor they omit during their breeding season (This author encountered it first hand this year due to some captive breeding trials). The following text is quoted from an 1888 Entomological Society of Washington commentary regarding an article discussing their occurrence:
"Mr. Smith read a paper on the peculiar odor emitted by Dynastes tityus. This is well known to entomologists, but during the present season, the species has developed into a pest. In two States -- Virginia and Tennessee -- they have been locally so abundant as to saturate the air with the penetrating stench. The local boards of health, especially that of Memphis, Tenn., disinfected all sorts of foul and suspected localities without success, and only by accident was the true source of the smell discovered. It must have required many thousands of specimens to have produced such an effect, and it is an interesting instance of a new way in which insects can render life burdensome to man. In discussing this communication Mr. Lugger said that the favorite food -plant of the Dynastes is the Water Ash (Fraxinus sambucifolia), which is quite common in the vicinity of Memphis."*See the Article, "Beetles as a nuisance," by J. B. Smith, in Popular Science Monthly, xxx, pp. 409-410.*
This remarkable literature note is pretty humorous given the thought of the many contemporary dandies languishing in what may have been this author's ideal atmosphere - so many beetles! However, the note also serves to exemplify how much our local environments have changed over the last century. As many readers may remember, Ash trees were once a ubiquitous feature among our native forests. Since the introduction of the Emerald Ash Beetle, that has taken a 180° turn. Ash trees have been devastated across the country, and the determent is still yet to be fully understood.
Eastern Hercules Beetle (Dynastes tityus) - Larval specimen observed in Culpepper, Virginia
@leealloway, some rights reserved (CC-BY-NC)
On the topic of trees and changing environments, there is another interesting factor to consider when discussing the ecology of the Eastern Hercules beetle. Age is an important factor when discussing forest health. An ecoregion needs to include a wide variety of successional habitat types to support the preferences for our local biodiversity. As the centuries have proceeded since European colonization the extent of old-growth forests has drastically declined. Gone are the days of old hemlock painting the Blueridge Mountains, and our beloved ancient oaks are now a rarity, usually standing as a reminder of an old cattle field. Old trees (and old-growth forests) provide immensely important habitat and ecological service that is often overlooked. In regards to our Hercules beetle, the species has a preference for trees bearing the marks of advanced age - the cavities, or hollows that develop after a long life of enduring natural abrasiveness. As rot and decay set into these hollows, it produces an ideal kind of substrate composed of decayed and fermented bark and heartwood, with which the female Hercules beetle lays her eggs. This substrate provides nourishment for the developing larvae but can be uncommon in the secondary and early successional forests since young trees drop very little woody materials as they develop.
Much like large mammal species, our large coleopteran species, like the Hercules beetle, can be good indicators of general forest health. Although the forests of the Bull Run Mountains are far from ancient - being mostly cleared in the last century - they are serving as an oasis for many species which are finding themselves more and more surrounded by the development and urbanization of the D. C. Metropolitan Area. Abundant hardwood species are and will continue to be able to develop into a primary forest in the future to come and by doing so provide an ever more important sanctuary of biodiversity in our region.
Note from the editor: ~They also really like oranges~ R.I.P. Hairy the Hercules beetle
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The Bull Run Mountains are the easternmost mountains in Virginia. Virginia Outdoors Foundation - Bull Run Mountains Natural Area Preserve is approximately 2,350 acres that serve as a living laboratory that sits in the backyard of our nation’s capital. The preserve contains 10 different plant community types and a plethora of regionally uncommon and threatened plant and animal species. In 2002, this land was dedicated by the Virginia Department of Conservation and Recreation as a natural area preserve to protect the unique ecosystems found here. As the owner and manager of the preserve, the Virginia Outdoors Foundation is committed to protecting the special ecosystem found here and sharing it with the public through managed access.
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