Feeds:
Posts
Comments

Archive for the ‘Identification’ Category

Mite-y Waist: Correcting a 60-Year Error in Mite Morphology

ENTOMOLOGY TODAY  LEAVE A COMMENT

Much of mite biology is clouded in mystery—even the delineation of their body segments. A new study upends a 60-year-old model for the proper location of mite “waists.” Shown here is a scanning-electron microscope image of a Proteonematalycus wagneri female mite. (Image by Sameul Bolton, Ph.D.)

By Samuel Bolton, Ph.D.

Samuel Bolton, Ph.D.

Most people are surprised to find out that mites live in more places than just inside their mattress or on their pets. But what we acarologists know about mites is, comparatively speaking, not so much more, for there is still a tremendous amount that we have yet to discover about these arthropods.

For example, our knowledge of global mite biodiversity is so meager that estimates of the total number of undescribed species of mites range across nearly two orders of magnitude—from 500,000 to 40 million. And our ignorance extends to some fairly basic aspects of mite biology. There are still competing ideas over the correct body plan for all mites. (See video, below.)

There is even a controversy over where one major body region ends and another begins. This particular controversy interests me because it illustrates how an influential idea can persist long after evidence comes to light that shows it is likely in error. When a bad idea becomes highly influential, often because the originator is influential or because the idea has aesthetic appeal, it can endure for long enough to become entrenched within the culture of a scientific community.

Mites are arachnids, and that means that they have a body that is divided into a prosoma (the limb-bearing region at the front) and opisthosoma (the limbless region at the back). To keep things simple, I will call the border between the prosoma and the opisthosoma the “waist.” This is apt because in most arachnids there is a waist-like constriction between the prosoma and opisthosoma, which makes it very easy to tell where the prosoma ends and the opisthosoma begins. But almost all mites lack such a visible waist.

In 1963, a well-known acarologist, Leendert van der Hammen, published a hypothesis on where the waist is positioned in mites. He proposed that the waist is delineated by a furrow, present in some mites, that runs obliquely from the top of the body to an area just behind the rear pair of legs (see Figure 1, top). However, there are other mites, such as Micropsammus, that have a body with a vertical furrow that looks a lot more like a waist (see Figure 1, bottom). The dorsal part of the vertical furrow is in a different segmental position to that of the oblique furrow. It is therefore not possible that the vertical furrow has reorientated to become the oblique furrow or vice versa, and so only one of these furrows can be the waist.

A model of a mite (top) shows the oblique furrow that Leendert van der Hammen thought was a “waist,” or the division between prosoma (the limb-bearing region at the front) and opisthosoma (the limbless region at the back). The image of a Micropsammus sp. mite (bottom), however, has a vertical furrow that looks a lot like a waist. (Image by Sameul Bolton, Ph.D.)

Most acarologists treat van der Hammen’s oblique furrow as the true waist. However, van der Hammen’s interpretation was based on oribatid mites, which have highly modified morphologies for defense, and so the oblique furrow seems more likely to be the result of a defensive modification than a true waist. Why, then, is his interpretation still widely accepted? One reason is that this is another example of a persistent and influential idea that is long overdue for retirement. Another reason is that almost all species of mites lack visible body segments. The waist is a segmental border that divides the prosoma from the opisthosoma. Without a series of clearly delineated segmental borders, it is difficult to know which of the two furrows is definitely a waist.

There is one mite, however, that does very clearly show its body segments, especially on the part of the body where the waist is. Proteonematalycus wagneri, which has been collected on no more than a handful of occasions, has been examined only very rarely. The description of P. wagneri, which is more than 30 years old, includes drawings of a segmented body that starkly contradicts van der Hammen’s interpretation. Drawings can sometimes be misleading, though. In a paper published in February in PLOS ONE, I analyze new detailed images of P. wagneri, which more clearly illustrate the flaw in van der Hammen’s hypothesis and offer a new model for mite body segmentation.

As seen in this image of a Proteonematalycus wagneri adult female mite, the oblique furrow is absent and so it cannot be the true waist. (Image by Sameul Bolton, Ph.D.)

The image in Figure 2 shows that P. wagneri has a segmental border that is in exactly the correct position and orientation to correspond with the vertical furrow of Micropsammus (Figure 1, bottom). That border is the true waist, not only because it divides the prosoma from the opisthosoma, but also because there is no sign of the oblique furrow. If you can clearly see the body segments but the oblique furrow is nowhere to be seen, that can only mean that the oblique furrow does not correspond with a segmental border, and so van der Hammen was clearly wrong about that furrow being the waist.

But why is it so important to know where the waist is? Well, as I mentioned above, the waist delineates the boundary between two major body regions, the prosoma and opisthosoma. If the oblique furrow were the true waist, it would mark out mites as very unusual compared to other arachnids. In an important way, Proteonematalycus wagneri shows that mites are not quite as weird as we had thought.

In fact, the position of the waist was correctly determined more than a century ago . But over the past half century, countless papers, including my own, have mislabeled characters as opisthosomal when they are prosomal. Almost 60 years of confusion and debate, all caused by one very influential paper that was written by one very influential acarologist. Oh, what a mitey waist.

Read More

Proteonematalycus wagneri Kethley reveals where the opisthosoma begins in acariform mites

PLOS ONE

Samuel Bolton, Ph.D., is curator of Acari at the Florida State Collection of Arthropods, in the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry. Email: samuel.bolton@fdacs.gov.

Read Full Post »

Crop leaf disease identification based on ensemble classification

Livestock and horticulture are well-known contributors to the global economy, particularly in countries where farming is the sole motivation for income. Yet, it is regretful that infection degeneration has affected this. Vegetables are a significant source of power for people and animals. Leaves and stems are the most common way for plants to interact with the surroundings. As a consequence, researchers and educators are responsible for investigating the problem and developing ways for recognizing disease-infected leaves.

Growers everywhere across the world will be able to take immediate action to avoid their produce from getting heavily affected, so sparing the globe and themselves from a potential global recession. Because manually diagnosing ailments might not have been the ideal solution, a mechanical methodology for recognizing leaf ailments could benefit the agricultural sector while also enhancing crop output. The goal of this research is to evaluate classification outcomes by combining composite classification with hybrid Law’s mask, LBP, and GLCM.

The proposed method illustrates that a group of classifiers can surpass individual classifiers. The attributes employed are also vital in attaining the best findings because ensemble classification has demonstrated to be much more reliable.

Read the complete research at www.researchgate.net.

Kaur, Navneet & V, Devendran & Verma, Sahil. (2021). Crop leaf disease identification based on ensemble classification. 

Publication date: Fri 10 Dec 2021

Read Full Post »

From Mapping to Management: A Revision of Soybean Caterpillar Pest Information for U.S. Soybean

ENTOMOLOGY TODAY1 COMMENT

Lepidopteran pests of soybean—such as the green cloverworm (Hypena scabra), shown here—are growing in importance in the U.S., and a pair of articles in the Journal of Integrated Pest Management provides updated guidance on biology, distribution, and management options for five leading caterpillar pests of soybean. (Photo by Adam Varenhorst)

By Erin Hodgson, Ph.D., and Anders Huseth, Ph.D.

Anders Huseth, Ph.D.

Erin Hodgson, Ph.D.

There never seems to be a dull summer when you’re an extension entomologist of field crops. Like Coolio said, there is always “sumpin’ new” happening in agriculture. Fluctuating pest populations and invasive species make our jobs interesting. Add in new chemistries and technology updates, and it’s hard to keep up with everything.

When a pest does establish and become a problem, we want to provide accurate identification and timely management recommendations. Unfortunately, many of our tried-and-true resources are becoming out of date. New extension folks have been especially frustrated by a lack of current resources. In particular, there is not enough current information on caterpillars feeding in soybean, though these pests are becoming more economically important in the U.S. and around the world. So, a few of us decided to create an update for some of the most prominent species in U.S. soybean. We represent five states spread across the nation: Florida, Iowa, Louisiana, Minnesota, and North Carolina.

caterpillar pests of soybean
corn earworm (Helicoverpa zea)
thistle caterpillar (Vanessa cardui)

To start, we surveyed field crop entomologists in all soybean-growing states to better understand current pest occurrence and abundance in soybean (approximately 83 million acres). We compiled data from all 31 soybean-producing states during the winter of 2020. Data indicated five species that consistently bubbled to the top of the list: green cloverworm (Hypena scabra), soybean looper (Chrysodeixis includens), corn earworm (Helicoverpa zea), velvetbean caterpillar (Anticarsia gemmatalis), and painted lady (Vanessa cardui, also known as thistle caterpillar in its larval form).

After summarizing survey information, we decided to write profiles on these species to improve identification, distribution, and scouting guidelines. Our group used older research and recent field observations to develop profiles of these key pests. Last, we wanted to focus on management, especially highlighting insecticide resistance issues starting to become prominent in some states. The results of this work are shared in two articles published earlier this year in the Journal of Integrated Pest Management—one on identification and biology and another on distribution and population persistence—with a third article still in the works.

Results from our survey provide a contemporary assessment of distribution and persistence of lepidopterans in soybean. Like the aforementioned rap artist says, field crop extension entomology is a “fantastic voyage,” and we hope the articles help provide updated information for caterpillar identification and management.

Read More

Identification and Biology of Common Caterpillars in U.S. Soybean

Current Distribution and Population Persistence of Five Lepidopteran Pests in U.S. Soybean

Journal of Integrated Pest Management

Erin Hodgson, Ph.D., is a professor and extension entomologist at Iowa State University. Email: ewh@iastate.eduAnders Huseth, Ph.D., is an assistant professor and extension specialist at North Carolina State University. Email: ashuseth@ncsu.edu.

Soybean Gall Midge: Discovery of a Delicate and Destructive New Species

March 9, 2021

New Guide Offers IPM Tips for Japanese Beetles in Soy and Corn

April 29, 2019

Learnings From Latin America: Potential Risk of Helicoverpa armigera to U.S. Soybean Production

February 1, 2021

Read Full Post »