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

Biodiversity Highlight (Series #1: Part Three): Ceruchus piceus (Red-rot Decay Stag Beetle)
Virginia Outdoors Foundation - Bull Run Mountains Natural Area Preserve


Ceruchus piceus (Red-rot Decay Stag Beetle) - minor ♂ spotted on The Preserve's north section

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


Hello again everyone!

Welcome back to yet another installment exploring the biodiversity of the Bul Run Mountains. This week's mention mark's the final stretch of our deep dive into the Lucanidae of the Bull Run Mountains. Armed with much more intimidating mandibles, a slick, yet stocky build, and an entirely different habitat preference than our previous highlights let's jump into our subject - Ceruchus piceus, or the red-rot decay stag beetle. Like our other Lucanidae, this particular species has the same voracious appetite for decaying wood (at least as a larva). However, this species requires another type of rotting wood from which it gets its common namesake - red rot More on that later though). The red-rot decay stag beetle is another diminutive species of Lucanidae (perhaps tied with Platycerus quercus), only reaching a maximum size of ~18mm (or about the size of a thumbnail). The species occurs relatively commonly across both undisturbed and even urban habitats where suitable deadwood occurs - just check out the locations it has been spotted around NOVA.

Typical of its family, the red-rot decay stag beetles have a geniculate antenna culminating in a multi-antennomere club at the distal end. The elytra of the species are striated, meaning they are marked with long, thin, parallel lines. The specific epithet of the species piceus translates directly to "pitch black" - a pleasantly literal representation of the species. One of three species of Ceruchus, this is the only species of the genus to occur within The Preserve and Virginia as a whole. However, should you come across a similar-looking species in the north or west, the males of this species can be identified by a large "tooth" present along the center of the mandible. Beyond identification and biological notes, this species has been the subject of some interesting scientific studies. Some of which involve the larval form of the organism's capacity to tolerate sub-freezing conditions without extensive use of anti-freeze alcohol, a technique typical of many freeze-tolerate insects. This may be a great topic to explore in a future winter-specific post on insects.


Ceruchus piceus (Red-rot Decay Stag Beetle) ♂ - male specimen observed in Massachusetts

© Tom Murray (@tmurray74), some rights reserved (CC-BY-NC)


Wow, look at those chompers! The major males (males that show exceptional development of mandibles and which approach or have reached maximum size) of this species are likely armed with the second largest mandibles relative to the body size of any other Lucanidae in the United States. Interestingly, unlike other species of stag beetles with such large mandibles, the red-rot decay stag beetle does not use its well-endowed appendages to secure the female during the mating process. In good taste, this stag beetle prefers to woo a receptive female by massaging her elytra with his midleg during mounting and mating. This behavior is interesting in that it excludes the function of the mandibles in courtship behavior. With the resource allocation needed for developing such weapons, they are restricted to male-on-male mate competition.

As promised earlier, let's have a brief look at some stag beetle ecology involving deadwood. It is just as important to understand the organism as it is to understand its habitat. In the family Lucanidae the habitat of choice is typically rotting, deadwood materials in forest environments. Many of us are familiar with rotting wood, whether in our own homes or having encountered it in a natural state. However, there are several types of rotting wood that have to provide very different resources to the surrounding habitat. The two main types are brown (or red)rot and white rot. These types of wood rot are determined by a panoply of fungal species associated with each type. Common species include Trametes versicolor (Turkey Tail), considered a "white rot" fungus, and Laetiporus sulphureu (Chicken-of-the-woods), considered a "red rot" fungus. These fungi consume different polymers found in dead wood leaving behind materials for which the rot types get their names.

In white rotted wood, the fungal species colonizing the deadwood break down the lignin of the wood, in turn releasing carbon dioxide and water. Once completed this process leaves an abundance of fiber-rich, white-colored cellulose remaining. This process is switched in red-rot-associated fungal species, which breaks down the cellulose of the deadwood and leaves behind the brown-red colored lignin. The brown lignin is also consumed in white rot fungi, but the polymer is "bleached" leaving the materials much lighter in color. The textures of these rot types are also distinct from one another. White rot is typically stringy or soft, highly fibrous, and very easy to pull apart. Red rotted wood tends to produce blocky, harder pieces of processed wood which can be very fractured in appearance.


Ceruchus piceus (Red-rot Decay Stag Beetle) ♀ - female specimen observed in Massachusetts

© Jason M Crockwell (@berkshirenaturalist), some rights reserved (CC-BY-NC-ND)


The preference of rot types between Lucanidae species has been recorded around the world. There have even been correlations between the size of rotted woody materials and the state of decay playing a role in habitat selection by females for oviposition. Some of this is understood, and much of it isn't specifically known. There are many mysteries and nuances left to be discovered in stag beetles!

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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.

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Publicado por mjwcarr mjwcarr, 05 de agosto de 2022

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