Biodiversity Highlight - Series #1: Lucanidae of the Bull Run Mountains - Part Four

Biodiversity Highlight (Series #1: Part Four): Lucanus capreolus (Reddish-brown Stag Beetle)
Virginia Outdoors Foundation - Bull Run Mountains Natural Area Preserve

Lucanus capreolus (Reddish-brown Stag Beetle) - ♂ spotted at Bull Run Mountain Estates (adjacent to The Preserve's Northern Property)

© Mark D Swartz (@markdswartz), some rights reserved (CC-BY-NC)

Hello again everyone!

Welcome to our fourth and final installment highlighting the Lucanidae of the Bull Run Mountains. I hope you all have enjoyed these articles as much as I have enjoyed writing them. This week's article will highlight the largest and most impressive species of stag beetle in our area. In addition, we will be covering some of the life histories, specifically their larval form. While the family Lucanidae is a personal favorite of mine, we have many more exciting Coleopteran species to explore in upcoming highlights. So let's get started!

Our subject for this week is the reddish-brown stag beetle, Lucanus capreolus. This species of stag beetle is among the largest of the stag beetles in the United States, only falling short of the larger giant stag beetles found in central and southern Virginia. These remarkable stags can be identified easily by their starkly bi-colored femora, chestnut elytra, and the large, sickled-shaped mandibles sported by the males. The species can reach sizes of up to 42mm (or just over 1 1/2 inches) depending on habitat quality. The species is more tolerant of upland, rocky habitats than the closely related giant stag beetle, supporting the probability of the species' presence within the mountainous terrain of The Preserve. This habitat adaptability is apparent when viewing the distribution of the species in the western portions of the state. Here, the species can be seen well within the mountainous habitats of the Blue Ridge and Central Appalachian Mountains in Virginia. Despite some effort from this author, the only observation of the species around the preserve has been on the Eastern slope of the Bull Run Mountain, outside of The Preserve - hopefully, this can be remedied soon by our visitors!

The scientific name of the species, Lucanus capreolus, echos the brain space of its European author - the Swedish Taxonmist Carl Linneaus, who formalized the system of binomial nomenclature. The specific epithet "capreolus" translates directly to "little goat", but derives its meaning from the European roe deer (Capreolus capreolus). This was due to the resemblance of the male stag beetles' mandibles to the antlers of the deer, which are common across the European continent. This likening to Cervid antlers is common in this Genus of Lucanidae. The Giant stag beetle (Lucanus elpahus), mentioned several times in this series, is named in relation to the European elk, Cervus elaphus. An interesting caveat is that both of these species are named in relation to European species which do not occur within the native range of either American species.

Lucanus capreolus (Reddish-brown Stag Beetle) ♀ - female specimen observed in Virginia

© Michael J. W. Carr (@mjwcarr), some rights reserved (CC-BY-NC)

Although males get much of the attention for this family of beetles, due to their well-endowed mandibular assets, the females possess an underappreciated charm. With an incredibly stereotypical beetle-ish form, female stag beetles can be difficult to identify without some nuance know-how. This becomes incredibly useful in the Southern portion of the state where several genera of Lucanuidae become more common and diverse. For this species, there are several main morphological features to pay attention to - size, color, a shape of specific morphological features.

Firstly, when finding a particularly beetle-ly looking beetle, identify it to family level Identification by looking at the antenna: geniculate (elbowed) with a distal club (several slightly flattened antennomeres) are a typical shape for local Lucanidae. Moving closer to identifying your beetle, get to the genus level by using several notes: size - L. capreolus species are between 22-42mm (42mm is the maximum male size),. The difference in size can be tenuous based on the health of the individual beetle during its larval stage. This is best used to rule out the diminutive species of Lucanidae like Platycerus and Ceruchus. Texture can help as well as the genus Lucanus generally has a smooth, almost glossy elytron which distinguishes them from a similar genus Dorcus (which has striated elytra). Regarding color, many of the Licanidae in our area are black in color (Dorcus, Platycerus, Ceruchus), but the rich, mahogany-chestnut color of the reddish-brown stag beetle will certainly set it apart in aesthetic depth. Finally, there is a fine morphological feature to pay attention to if you want to get your identification down to species level, especially for females. A feature known as the labrum, which sits between the mandibles, is notably triangular with a rounded tip. This point of reference is absolutely necessary to look at when determining female Lucanus species apart.

Okay. Now that I've frontloaded all of that information there is an easy, quick identifying feature for identifying the species - their bi-colored femora (as seen in both the male and female specimens pictured in this article). These bright orange femora are distinctive among all North America Lucanidae, so make sure to take ventral pictures of this family if you're still not confident in your identification.

Lucanus capreolus (Reddish-brown Stag Beetle) - Larval specimen observed in Massachusetts

© mistaharris (@mistaharris), some rights reserved (CC-BY-NC-ND)

If you're a gardener the specimen above may look vaguely familiar. The white grub, technically described as scarabaeiform larvae, is a catch-all for the diverse and convoluted category of larval beetles which can be incredibly difficult to identify without a scope or a keen eye. The Lucanidae larvae fall under this category and can easily be mistaken as garden pests (like the Asian garden beetle, Maladera castanea). This misidentification can be somewhat avoided based on the context in which a white grub is found - among the living roots and soil of a garden a good habitat for stags it is not. As stated throughout this series this family of beetles is saproxylic or requires dead woody materials for their development. As such, this family is typically found within decaying stumps, rotting logs, and scattered soil-submerged branches.

This preference for woody materials can lead to some overlap of natural and artificial environments. The species has remarkably been found to be somewhat flexible in the medium in which they can develop. Railroad ties, landscaping mulch, and compost have all been found to support larval stag beetles. This adaptability to more urban woody resources provides an interesting dichotomy within the literature, which, until recently, has always associated the family with more old-growth landscapes. This is made even more impressive when you consider that the development of larval stag beetles into adults can be as much as three years.

If you do come across a white grub and are curious to tell whether it is a Lucanidae larva, there is a way. Stag beetle grubs have several morphological features that distinguish them from their closely related scarab cousins. This comes in the form of 'C' shaped spiracles, or the darkly colored dots running laterally along the body of the grub. In other scarabaeiform larvae, these are typically complete circles. The head capsule is also considerably larger than other scarab larvae, and armed with darkly colored mandibles that extend somewhat outwardly - what out, they can nibble! Finally, if you are comfortable handling the grab and acting outside of human norms, take a look at its rear-end. The anal aperture of the grub will be 'y'-shaped or longitudinal.

Thank you for reading! If you enjoyed this short article please leave a comment below to help us gauge community impact for our annual summary. Additionally, if you have any questions, comments, or corrections leave them below. While niche, this platform provides a unique opportunity for naturalists and enthusiasts to share their insights and stories regarding the amazing biodiversity that surrounds all of us.

If you are interested in visiting the Bull Run Mountains Natural Area preserve or attending public events, please check the links below for more information.

ABOUT #BullRunMountainsNaturalPreserve
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.

Follow us on Social Media!
iNaturalist: VOF-BRMNAP Preserve Manager Joe Villari (@jvillari)
Instagram: @bullrunmountains
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Meetup Events: Bull Run Mountains Natural Area Preserve Guided Hikes Group

Posted on 11 de agosto de 2022 by mjwcarr mjwcarr


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