Pestology Blog
Spider Heartrates, Rancid Fats, and Love Pheromones
Fairfax, VA – February 1, 2025
In the February 2025 episode of NPMA BugBytes, cohosts Ellie, Laura, and Mike were joined by special guests Noelle and Rian Goins of Get Goins Pest Control! We covered new research on the Joro spider heartrates, rancid fats used to repel pests, and pheromone control for the Indian meal moth.
Featured Article Summaries
Joro Spider Heartrates
How to Give a Spider a Heart Attack: Evaluating Cardiac Stress Reactions of Trichonephila and Argiope Spiders
It’s unfortunately all too common for insects, rodents, and other pests to stow away in shipped goods that get transported from their native range, where they may end up in a new region on the other side of the world. Once they land, they can become damaging invasive pests capable of spreading throughout the new non-native range. One key to stopping these invaders in their tracks is to understand how and why they can spread in a new environment. For most pests, the reasons are simple. The new climate is favorable, there are no natural predators, and there is an abundance of food. But, sometimes, the reasons can be pretty unique as researchers Andrew Davis and Christina Vu at the University of Georgia learned with the invasive spider, Trichonephila clavate, more commonly known as the Joro spider.
The Joro spider is a type of orb-weaving spider that is a somewhat new invader to North America originating from East Asia. It was first confirmed in northeast Georgia in 2014 and is thought to have made it’s way to the US accidentally on cargo ships. These spiders are pretty easy to spot thanks to their brightly colored yellow and black bodies that can measure more than 1-inch long. When you add their leg-span into the overall size, they measure about 4 inches. To top it all off, these spiders tend to thrive an suburban areas and are capable of building webs that can reach up to 10 feet wide. This all makes for an intimidating arachnid to anyone who gets the heebie-jeebies around 8-legged critters. Luckily, these spiders don’t pose much of a health threat to people, but this spider could outcompete native species making them an ecological concern. Since this spider made landfall in 2014, they have continued to spread and are now found as far north as North Carlina with no signs of stopping. In fact, some range models suggest that, given their physiology and native range, the Joro spider could thrive as far north as Canada if it’s not stopped.
To better understand how the Joro spider is thriving in the busy urban habitats this species prefers in the US, researchers investigated how this species deals with stress. All animals deal with stress, and some are better at it than others. Generally, stress disrupts an animal’s normal behaviors such as looking for food, mating, and sleeping. The longer or more sever the stress is, the more these processes can be disrupted. To measure how the Joro spider deals with stress, researchers monitored the spider’s heart rate during times of inactivity and times of stress, and compared those measurements to a close cousin of the Joro spider, the golden silk spider (T. clavipes) which is a native species in the US as well as two other similarly-sized orb-weaver spiders, the garden spider (Argiope aurantia) and the banded garden spider (A. trifasciata).
Figure 1. Procedure for obtaining data on ‘baseline’ or ‘resting’ heart rates of spiders. Mature female spiders of each species were collected and housed in custom-built wooden frames with transparent plastic walls. The spiders could build webs (like the one pictured) or simply remain on support strands, but in all cases, were inactive during recording. We used a horizontally mounted microscope video camera to film 30 s of footage focused at the center of the abdomen, where the dorsal vessel (heart) could be seen pumping under the cuticle (location marked with dotted line).
To accomplish this study, Davis and Vu first measured baseline heart rates for 10 minutes for each of the four spider species while the spiders were inactive (Figure 1). They did this by videoing and counting the dorsal vessel pulses of each spider over a 30-second period. They then recorded heart rates for 10 minutes while the spiders were physically restrained, using an electronic optocardiographic sensor to log cardiac movements over time (Figure 2).
What their data showed was that heartrates for all four species increased when the spiders were stressed, but that the variability of heartrates, or the difference between resting and stressed heartrate, for both the Joro spider and its cousin the golden orb weaver was lower. The researchers noted that that neither spider struggled much when under restrained. The other orb weavers, on the other hand, were observed frequently struggling when pinned down, leading to a much higher heart rate under stress.
Davis and Vu suspect that the ability of the Joro spider and golden orb weaver to remain cool under pressure may be a survival strategy that gives them an advantage during times of stress and could be a key to how the Joro spider thrives in the busy urban habitats that this species prefers.
Article by Mike Bentley, PhD, BCE
References
Davis, A.K. & Vu, C. (2025) How to give a spider a heart attack: Evaluating cardiac stress reactions of Trichonephila and Argiope spiders. Physiological Entomology, 50(1), 38–47. Available from: https://doi.org/10.1111/phen.12463
Rancid Fats as Pest Repellents
Rancid Rumors or Native Wisdom: Evaluating the Efficacy of Animal Fats as Insect Repellents Attributed to Historic-period Native Americans
People have been dealing with mosquitos for all of human history. The itchy annoying bite of these insect pests transcends time and cultures. In this study we go back to a time before DEET and picaridin were available and before repellents of any kind as we know them today were an option. In fact, this paper takes us into the world of the Native American people prior to and following the initial European contact. It is important to note that malaria did not exist on this continent before it was brought by Europeans, so while mosquitos were an annoyance, they were less of a disease threat than they were for the rest of history as we know it.
But back to how I started this tale, the mosquito bites. There are several historic accounts about how Native people may have fended off these pesky insects. These accounts record that Native people around the gulf coast area used rancid animal grease as a mosquito repellent. There are notes from primary historical accounts from 1700s and 1800s around the area. These accounts show the European’s disgust with the methods used and this repulsion compounded their negative impression of the native people who were just using what they had to coexist with their surroundings. The smell of the treatment contributing to a cultural clash is a classic example of olfactory ethics- but I digress.
In this study, the researchers looked at the grease of bear, alligator, shark, and cod. They hypothesized that the more rancid fats would repel mosquitos but they tested them against both mosquitos and ticks for good measure.
Fig 1. Ethnohistorically reported use of animal fats as insect repellents. Shown are regions within in the Gulf of Mexico that have historically documented use of specific animal fats as repellents. This image was generated using Adobe Illustrator 25.4.1 https://www.adobe.com/products/illustrator.html. The base map was generated by QGIS 3.34.3-Prizren https://qgis.org/en/site/ using raster and physical data from Natural Earth https://www.naturalearthdata.com/downloads/. Note: This map does not represent or intend to represent official or legal boundaries of Indigenous nations.
They looked at differing levels of rancidity from freshly harvested, to left out for 1-3 months. Rancidity happens when fats are exposed to oxygen over periods of time and the fat molecules begin to break down. They scored levels of rancid-ness based on people smelling them. Alligator oil was the most rancid and shark oil was the least based on smell assessments.
For the tick side of the experiment, they used Ixodes scapularis, the deer tick. For repellent effects on the tick, they found that only alligator oil and shark oil worked for less than 10 minutes against them, so while it was an interesting idea to test, it didn’t work much.
For the main part of the experiment, the mosquitos, they used Aedes aegypti, the yellow fever mosquito to test out for mosquito repellency. For one part they used a y-tube choice design where the mosquitos could go towards either the fat covered arm or the empty side. And then for a more direct approach, volunteers put their arm into an arena with 25 mosquitos to see if they would bite the area covered in the fats.
Cod oil and alligator oil provided the longest protection from bites on skin with an effective time of over 1 hour. These and bear fat both were effective in repelling mosquitos in the choice tube arenas. Across each animal, the more rancid versions of these were more effective than the fresh. The scores from people smelling them also correlated to the molecular analysis of the fats, proving that the smell reported in the historical accounts meant the fats were rancid and that changed the chemical makeup of the material.
Native people used animal fats in a multitude of ways including food and medicines, with some reports saying the fats were used as lotions and even sunblock. While the repellency of these fats was relatively short lived compared to repellents today, it was better than nothing. Since we have so little information from the historic accounts, we cannot discount the possibility that the animal fats were combined with plant materials too. In other medicinal uses, fats were combined with plant materials but the study had to start somewhere, so it is possible that a more effective solution existed. The researchers made efforts to contact the contemporary indigenous peoples of the area for comments and input but were unable to obtain any. This is why they relied on the historical sources available.
Future studies could look at other species of mosquito, but generally Aedes aegypti is the one recommended for such testing. I think the molecules that indicate rancidity may have merit to be explored in the context of future repellent development either on its own or potentially as synergists for other compounds used. Many insecticides and repellants we use today are based on the natural world so looking at human history to see what methods may have been used before, could be key to innovating in the future.
Article by Ellie Sanders, BCE-Intern
References
Esmaeili D, Salas KR, Luker HA, Mitra S, Galvan CJ, Holguin FO, et al. (2024) Rancid rumors or Native wisdom: Evaluating the efficacy of animal fats as insect repellents attributed to historic-period Native Americans. PLoS ONE 19(7): e0301677. https://doi.org/10.1371/journal.pone.0301677
Pheromones in Indian Meal Moths
Evaluation of Microencapsulated Liquid Pheromone for the Control of Indian Meal Moth (Plodia interpunctella) in a Retail Environment
Stored product pests, such as the Indian meal moth, Plodia interpunctella, are frequently managed with traps and dispensers that utilize synthetic pheromones. The goal of these products is to saturate the environment with the synthetic version of the sex pheromones of female moths. This process, known as mating disruption, prevents males from finding females. Without the boy-moth-meets-girl-moth, the pests are unable to reproduce and therefore are unable to grow the population, leading to effective management.
The purpose of this study was to evaluate the potential of using microencapsulated liquid synthetic pheromones in commercial retail settings to manage populations of Indian meal moths. The researchers chose four pet stores in the surrounding area that featured similar layouts and products sold. They began by using pheromone traps to measure the current populations of Indian meal moths in each of the stores. Following that baseline measurement, the microencapsulated pheromone was applied at the label rate in three of the stores, while one was left as a control. The microencapsulation was applied using a battery-powered backpack sprayer under shelving units, walls, and unreachable corners of the store. Applications were made every 90 days over the course of a year (so a total of three times), and monitors were retrieved, counted, and replaced monthly. Monitors were placed in specific areas of the stores to track not only how the population fared overall, but to measure if certain products sold were more appealing at certain times of the year.
Overall, the researchers found that the microencapsulated liquid synthetic pheromone could effectively reduce Indian meal moth populations in commercial settings. Particularly, the application of the microencapsulation every 90 days was the most effective in the stores that featured low to medium infestations, which the researchers counted as 15 moths or less per trap in each monthly check. In these cases, the researchers were able to document an 85.8-95.2% reduction in the Indian meal moth populations over the course of the year. The store that featured a “high” population of Indian meal moths still saw a reduction, but only at 33.8%. This data tracks with other mating disruption products, as the more individuals there are in a population, the more likely they are to meet each other and continue the population, despite the synthetic siren song that may be in the area.
The researchers additionally tracked how these pest populations fluctuated over time, but also how they fluctuated across the stores. All stores showed an increase in moth captures during the months of October and December. The researchers speculate that this increase may be due to moth displacement from both new holiday products as well as increased consumer traffic disturbing the shelves. However, the researchers hypothesized these bumps in the population may also be due to the increase in return of damaged products, which may provide opportunities for the moth populations to grow. Unsurprisingly, the areas that featured dog and cat food often saw the highest numbers of Indian meal moth captures, suggesting that these products may be either the original source of an infestation, or could be an attractant. Additionally, the backrooms of these locations showed high populations of moths, which is likely due to the storage of damaged products, or new products that are awaiting placement on the shelves. Overall, this data provides more context for the best times and locations to treat Indian meal moth populations in commercial settings.
This study provides a promising look at a new potential product for management of Indian meal moth populations in a commercial environment. As we well know, commercial environments can be some of the trickiest to treat, considering they are often areas of high movement, with limited available products to use, and require management strategies that are out of the public eye. Not only is this product potentially more cost effective with applications every 90 days, it also may act as a preventative tool that could potentially help stop populations from starting.
Article by Laura Rosenwald, BCE
References
Jessica C. Lindenmayer, James F. Campbell, James F. Miller, Alison R. Gerken,
Evaluation of microencapsulated liquid pheromone for the control of Indian meal moth (Plodia interpunctella) in a retail environment, Journal of Stored Products Research, Volume 110, 2025, 102479, ISSN 0022-474X, https://doi.org/10.1016/j.jspr.2024.102479.
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