Biodiversity Highlight - Series #3: Scarabaeidae of the Bull Run Mountains - Part Three

Biodiversity Highlight (Series #3: Part Three): Pelidnota punctata (Grapevine Beetle)
Virginia Outdoors Foundation - Bull Run Mountains Natural Area Preserve

Pelidnota punctata (Grapevine Beetle) - Adult specimens observed on the Northern Sections of The Preserve

© Jared Gorrell (@wildlandblogger), some rights reserved (CC-BY-NC) [Left]; © Michael J. W. Carr (@mjwcarr), some rights reserved (CC-BY-NC) [Right]

Hello everyone,

Welcome back the to our biodiversity highlight series on the Scarabaeidae of The Preserve at Bull Run Mountains. This week's entomological deep dive will be the third installment of our series investigating the Scarab beetles found within the richly diverse forests and hollows of the preserve. Through our previous articles, we’ve seen that the taxonomy of the scarabs can be useful (or confusing) in determining how we can differentiate and categorize the various species found within this large family group. We’ve also seen that the abundance of some scarabs has declined with the anthropization of habitats in the developing United States. This week’s highlight will continue in highlighting some of these topics and in broadening our understanding of the related natural systems by including a species from yet another scarab subfamily - the grapevine beetle, Pelidnota punctata. This remarkable “big beetle” of the preserve can be easily identified by its distinctive yellow-tan color and the adornment of six dark spots along the margins of its elytra (for which the species gets its namesake). Circling back to our inaugural scarab highlight, this species name is derived from greek and Latin roots attributed to its physical appearance, something any Latinophile or classicist can appreciate. The genus name Pelidonota comes from a greek root, Pelidn, which roughly translates to livid, black, and blue. While not very representative of our golden child, this name represents some of the brilliantly black and blue-colored members of the genus that can be found in South America. Taking another step into the etymology of the species, the specific epithet is derived from the Latin root, punctat, which translates to - you guessed it - punctures! These names fit remarkably well and has surprisingly not changed much since the original description of the species by Linneanus as Scarabaeus punctatus in 1775.

Taking a step up, taxonomically speaking, let's look at what this beetle represents in our exploration of subfamilies within Scarab beetles. This beautiful beetle is a member of the Rutelinae subfamily, better known as the shining flower chafers (there is that chafer name again)! In comparison to our last highlighted subfamily group, the Rutelinae is a small to moderate subfamily of scarabs including approximately 4,100 species worldwide. The shining flower chafers are represented by only about 6 species North of Mexico, but the diversity skyrockets as you continue south toward the tropics. This subfamily is also known for the brilliant colors and iridescent to occur in many of its species - which is somewhat visible on our local Pelidnota. The Genus Pelidnota contains some 100 species, being the most species in South America. The members of this subfamily closely resemble the members of our previously highlighted subfamily member, the rose chafer of the Melolothinae, and is debated by some to be the sister group to the Dynastinae. However it will eventually be classified, the complexity of taxonomic classification is on full display within the parent taxonomy of our grapevine beetle.

Pelidnota punctata (Grapevine Beetle) - The life cycle of the grapevine beetle - Larvae > Pupa > Adult

© cyansnowflakes, all rights reserved [Left & Center]; © Joel Haan, all rights reserved

Let’s ground ourselves a bit here. Higher-level taxonomic descriptions only go so far in bringing an individual species into the spotlight. Taking a closer look at the grapevine beetle is key to developing an appreciation of an organism within the context of its environment. Taking a step down our taxonomic ladder, let's look at what makes the grapevine beetle what it is. Coming at a whopping 17-33mm in length, the grapevine beetle won’t be sparing with the eastern Hercules beetle, but it is quite large compared to the many species of beetle found in our area. Like our previous species, the grapevine beetle is fairly ubiquitous across the eastern united states and southeastern Canada and ranges from Texas and Florida north to southern Ontario and Quebec. Its preferred habitats include deciduous forests, thickets, “woods”(whatever that means), vineyards, and gardens. The last two habitats are listed in association with their diet and namesake - grapevine. Adult beetles are voracious consumers of grapevine, both cultivated and wild varieties. Despite this, the species is not considered a pest, or to cause significant damage to grape crops. This appetite results in the skeletonization and defoliation of host plants, and even the consumption of fruiting bodies. The species has also been documented on Virginia creeper, consuming both foliage and fruit. The larvae of the grapevine beetle appear as scrabiaeform white grubs and have a much more diverse assemblage of host species including maple, oak, hackberry, apple, elm, sycamore, and walnut. An interesting divergence from the grape-centric behavior of the adult form of the species.

While on the subject of natural history let’s take a look at the life cycle of the Grapevine beetle! This species has about a two-year developmental duration with the eggs being deposited in the summer, the larvae overwintering and pupating, and then eclosing from their underground chambers as an adult beetle in the following year. The flight season for adult grapevine beetles is between May and august. During this flight and dispersal period, the species is very attracted to lights, especially UV/metal halide lights. Using insect surveying equipment, including a Mercury vapor lamp, is how the two initial photographic examples were found at the preserve! Another interesting note on the species and how they may be encountered here on the Preserve is that the species exhibits physical variation depending on their distribution. Split into two groups, the southern examples of the species are known to have completely pale/tan legs which resemble the color of the rest of the body. The more northern phenotype has dark, nearly black legs and darker patches along the margins of the head capsule. While only southern variations of these phenotypes have been found on beetles found at the preserve, both phenotypes occur in our area.

Keep an eye out and record the first example of the northern phenotype at the Preserve!

Pelidnota punctata (Grapevine Beetle) - Examples of phenotypic variation among northern and southern populations: The pale-legged southern form [Left] and the dark-legged northern form [Right].

© Royal Tyler (@royaltyler), some rights reserved (CC-BY-NC-SA)[Left]; © Stephanie Eakin (@papilio-nikonis), some rights reserved (CC-BY-NC)[Right]

To close out this week's highlight I would like to take a brief look at the host species of choice for grapevine beetle - grapes, or Vitis! To the chagrin of the author, the varieties of grapes found on the preserve have not been well documented here on iNaturalist, despite being plentiful. Only two observations represent documentation of the species, and those were only at genus-level identification at the time of this article. Vitis is a widespread genus occurring across North, Central, and South America, the west indies, and Eurasia. The species has also been prolifically introduced around the world. Including some 70 species across the globe, the Vitis are also locally diverse with some six species occurring in Virginia. Several species have been noted in the literature to occur within the Preserve, including Vitis aestivalis var. bicolor (Silverleaf grape), Vitis labrusca (fox grape), Vitis cinerea var. floridana (Florida pigeon grape), and Vitis vulpina (fox grape, again). Some of these species also have several varieties that may or may not have been introduced by the inhabitants within the confines of the richly storied and settled Bull Run Mountains.

While these species have been recorded within the rich botanical literature of the Bull Run Mountains, they are not discussed as commonly as one would think given their ubiquitousness in the northern spaces of the preserve. This may be due to the relatively young nature of the forests of the Bull Run Mountains. Having been mostly cleared in the centuries prior, the Bull Run Mountains now stand as a champion of preservation in a now mostly developed Northern Virginia. With that implication comes some interesting questions as to what can be expected as the forest continues to age - how will the species assemblage change? what role will recently introduced invasive species will play? and whether there are still novel species waiting to be discovered in its mountain refuges? This week’s highlighted species was probably not a common sight in the century prior, preferring the more forested habitats that may have been known further north and west. By recording our observations now we can provide a small piece of evidence in noting the natural history of the Bull Run Mountains for generations to come - when the Bull Run Mountains are something different from what they are now. For this reason, I thank everyone who has involved themselves in recording the flora and fauna of the preserve. Keep up the good work!

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, professionals, 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.

Please note that the VOF-owned and operated Bull Run Mountains Natural Area Preserve is protected by the Commonwealth of Virginia under the Virginia Department of Conservation Recourses. Except for certain specific situations, camping, fires, unleashed pets, hunting, off-road vehicles, and removal or destruction of plants, animals, minerals, or historic artifacts are prohibited. Please respect our community's natural and cultural resources.

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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Posted on 21 de octubre de 2022 by mjwcarr mjwcarr


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