Project Overview

Reports

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Target Pests

Practices

Scorpions, predatory arachnids in the order Scorpiones, are distributed worldwide excluding Antarctica. There are over 2500 species of scorpions with most considered to be beneficial arthropods. However, approximately 104 species are considered medically relevant with 101 of these belonging to the family Buthidae. In the Americas, the prevalent genera of medically relevant scorpions are Tityus and Centruroides with 37+ and 24+ medically relevant species. Centruroides species are primarily found throughout Central and North America with Mexico having the vast majority of medically relevant Centruroides species. The U.S. contains only a single medically relevant scorpion species, Centruroides sculpturatus, which can be found from California to Texas with some populations in the four corners area. The highest prevalence of these scorpions however is in Arizona for where they got their colloquial name, Arizona bark scorpions (ABS). While ABS were originally only a problem in low-density housing areas near open spaces, these scorpions have become a prevalent pest in areas of high-density human populations. Hundreds of these scorpions can be collected in areas of less than a few hundred meters in suburban areas of the Phoenix metropolitan area.

Proximity of high-density human populations and large populations of ABS has led to numerous envenomation incidents with thousands reported to poison control centers every year. Generally, only those resulting in a hospital visit are reported, which underestimates the total number of envenomations. The annual number of scorpion stings is often larger than the number of envenomation events of snakes and spiders combined. Centruroides sculpturatus produces a class III sting, meaning that envenomation by this species could result in severe and life-threatening symptoms. The most common symptom is intense pain lasting for several hours or days. Some individuals may experience local or regional paralysis with the most dangerous symptoms being the potential for vital organ failure—cardiac and respiratory. Envenomation of an infant or small child necessitates medical care and often hospitalization. Because of the human health risk of ABS, there is a low tolerance for scorpions in homes and workplaces. The application of insecticides is a common practice, although most products have poor efficacy. Some insecticides may have a repellant rather than lethal effect on scorpions.

We are proposing a multi-objective approach utilizing alternative strategies from related fields of entomology and adapting them for urban usage against ABS. Our objectives include determining the presence and activity of scorpions during lunar fluctuations to develop spray techniques that target periods of active foraging. This will be done both in the field and in lab to verify whether there is an effect of lunar light and cycle on ABS activity. Secondly, we will evaluate the resistance levels of urban populations compared to natural populations to active ingredients of commonly used insecticides, primarily pyrethroids. Evaluating the most used classes of insecticides will help elucidate their effectiveness against ABS when used as a spray. Both objectives will help create strategies that could be utilized to control ABS populations and help forward the development of Integrated Pest Management (IPM) techniques.

Objective 1: Preliminary Analyses on the Relationship between ABS Presence and Lunar Cycle

1. Field Analysis of ABS Activity and Lunar Light Fluctuations: Understanding how ABS activity correlates with lunar cycle fluctuation is essential for developing IPM strategies targeting scorpion behavior. This objective supports WIPMC priorities for "Urban Pest Management" and "New Technologies to Manage Pests", given the lack of ABS control protocols based on behavioral insights.
   • Methods: In the field, teams will count scorpions at three independent locations twice monthly—once during the full moon and once during the new moon—over five months (June-October). Parameter measurements will include lux at ground level, temperature, humidity, and windspeed at each location.
   • Expected Outcome: Based on prior sampling from these sites we anticipate gathering sufficient data to conduct comprehensive analyses, with a high likelihood of success over the sampling period.
2. Controlled Lab Experiment on ABS Light Avoidance: This experiment will verify whether urban-caught ABS exhibit avoidance behavior toward specific light wavelengths, potentially informing the development of a scorpion-deterrent device. This directly supports the “New Technologies to Manage Pests” priority.
   • Methods: Scorpions collected from urban sites identified in the first experiment will be exposed to light wavelengths informed by prior research (Zwicky, 1970; Gaffin et al., 2011). A device has already been constructed that integrates programmable laser systems capable of emitting specific wavelengths, allowing precise testing of ABS phototactic responses. Scorpion behavior during exposure will be recorded using EthoVision® (Noldus North America, Leesburg VA) software to measure avoidance parameters, including the time spent in illuminated areas and velocity when moving away from the light source.
   • Current Progress and Potential Impact: The device, already operational, provides a reliable framework for exploring phototactic behavior. Its modular design allows for easy adjustments to test different light wavelengths. If specific wavelengths are confirmed to trigger avoidance behaviors, this could directly lead to the development of practical scorpion management tools.
   • Expected Outcome: With the foundational device already constructed we anticipate clear and replicable results from this experiment. This work validates the potential for light-based scorpion deterrents.

Objective 2: Assess Resistance Levels in Urban ABS Populations from Areas of High and Low Relative Insecticide Usage.

1. Resistance Comparison of Urban ABS Populations: Determining insecticide resistance levels in urban-caught ABS compared to less-managed populations is crucial for identifying effective formulations and guiding rotation strategies to delay resistance buildup. This objective directly addresses the WIPMC “IPM for Pest-Resistance Management” and “Urban Pest Management” priorities.
   • Methods: Dose-response assays will be performed on scorpions from urban environments of different levels of relative insecticide management to compare resistance levels. The assays will assess LD₅₀ values for pyrethroid and organophosphate formulations, as well as neonicotinoids depending on collection numbers.
   • Expected Outcome: We expect to collect enough scorpions from urban sites with relatively high and low insecticide usage. Scorpions have previously been observed and collected in the hundreds in these locations and we have a high probability of gathering the necessary samples within the study’s timeframe.