Tag Archives: Medical Entomology

Big Bugs, Medical Entomology

Scorpion Hitchhikers in Wisconsin

While scorpions are common in southern parts of the US, they aren’t native to Wisconsin or the Upper Midwest. Occasionally, they show up in the state as hitchhikers from other locations. In the last decade, I’ve seen only a handful of cases where scorpions were spotted in the Badger state. Interestingly, I’ve now had three reports of live scorpions submitted to the UW Insect Diagnostic Lab this year—from Milwaukee, Madison, and recently from Prairie du Chien (as shown in the video clip below). In the rare cases that scorpions do make an appearance, they tend to be the striped bark scorpion (Centruroides vittatus) or a close relative.

 

The striped bark scorpion is one of the most commonly encountered scorpions in the United States. This arachnid can reach lengths of roughly 2½ inches. It typically has a beige or yellowish body with two dark stripes running down its back—hence the name. They also have a dark triangular pattern near the eyes at the front of the body, which can help distinguish them from other species.

The striped bark scorpion is primarily found in the south-central United States, with most sightings coming from Texas. Its range extends west to New Mexico and eastern Colorado, and as far northeast as the St. Louis area. The species is also present in Mexico. Occasional sightings have been reported outside this typical range. In their natural habitat, these scorpions prefer secluded spots such as under loose tree bark, logs, rocks, and woodpiles. They may also seek shelter near buildings and can inadvertently wander indoors.

A striped bark scorpion found in a home in Prairie du Chien. Photo credit: PJ Liesch, UW Insect Diagnostic Lab.

Like many other scorpions, striped bark scorpions are nocturnal and are mostly active after dark. These arachnids are generalist predators, hunting insects and other small arthropods. They use their pedipalps (“pincers”) and telson (“stinger”) to subdue prey. While technically venomous, the striped bark scorpion’s venom is relatively mild and not considered medically dangerous to humans. However, stings from this species can still be quite painful.

Do the three reports of live scorpions mean that these creatures are becoming more common in our area?  No, not necessarily.  While it’s hard to tell how the range of scorpions may push northwards with climate change, we’re still well north of the native range of species like the striped bark scorpion.  The vast majority of Wisconsinites will never see one of these creatures in the state outside of captivity.  If anything, the three cases this year may simply illustrate how scorpions can be moved around by humans under the right conditions.

Biting Insects, Medical Entomology, Pollinators

Do mosquito yard sprays harm other insects?

If you’ve noticed all the lawn signs for mosquito treatments, you may be wondering if mosquito yard sprays harm other insects. If so, you’re not alone.  As an Extension entomologist, this is a common question that I get from the public every year.  To get to the bottom of this question, it helps to understand the different types of mosquito spraying that’s done.

One approach (Ultra Low Volume or ULV) is sometimes used by municipalities or abatement districts to control mosquitoes.  These ULV applications generally involve using specialized equipment mounted on trucks or aircraft to apply extremely tiny droplets which kill adult mosquitoes by direct contact as the droplets float in the air.  Such applications use very small volumes of insecticides either undiluted or with minimal dilution and are often applied after dark when mosquitoes are most active.  The microscopic droplets from ULV treatments disperse relatively quickly and have little residual activity—think of them like a “one time strike” to knock down mosquito numbers.

The vast majority of research on mosquito sprays and non-target organisms has looked at these ULV-type treatments.  Some good news is that these studies suggest that impacts to non-target insects are relatively small and short-lived.  It turns out that the ULV treatments are most effective on insects with very small body mass, so insects larger than mosquitoes tend to be spared.  A good summary of the impacts of ULV treatments on non-target organisms can be found in a 2012 review paper by J.A.S. Bonds in Medical and Veterinary Entomology. 

Many mosquitoes like to rest on vegetation during the day, so some mosquito sprays specifically target these resting sites. Photo credit: Public Domain Image.

Case closed, right?—Not quite. Here in Wisconsin, we don’t really use ULV treatments a whole lot for mosquitoes.  The common yard treatments are what we’d call “perimeter”, “barrier”, or “residual” treatments.  Such treatments are applied via a backpack sprayer to create a coating or “barrier” on treated surfaces which affects mosquitoes that land on it.  These treatments involve applying a residual insecticide (usually from the pyrethroid group) to vegetation in yards and around structures.  The pyrethroid products are broad-spectrum and often last for a few weeks or longer depending on the formulation.  These same ingredients (and sometimes the exact same products) can also be used to control a wide range of yard, garden, and structural pests (e.g., Japanese beetles, garden pests, household ants, etc.).

While the pyrethroids are very common and widely used for a range of purposes, there’s a knowledge gap when it comes to the impacts of mosquito “barrier” treatments on other insects.  While this knowledge gap exists, a few studies raise concerns.  One study by Dr. Karen Oberhauser and colleagues found that monarch caterpillars could be harmed or killed even 3 weeks after spraying.  A more recent (2022) study by Qualls et al. found that honey bees were harmed 28 days after “barrier” treatments were applied.  Thus, if a yard is being sprayed for mosquitoes monthly during the warm season, there are reasons for concern.  More research is needed to help understand the effects of these “barrier” yard treatments on insects that often land on vegetation in yards, such as moths, butterflies, fireflies and other beetles, true flies, bees, wasps and other pollinators.  

Fireflies can be very common on vegetation in a yard during the summer months. Scientists view pesticides as a concern for fireflies globally. Photo credit: RachelEllen via FLickr CC.   

References:

  • Bonds, J.A.S. 2012. Ultra-low-volume space sprays in mosquito control: a critical review. Medical and Veterinary Entomology. 26: 121-130. 
  • Oberhauser, K.S., Brinda, S.J., Weaver, S., Moon, R.D., Manweiler, S.A., and N. Read. 2006. Growth and Survival of Monarch Butterflies (Lepidoptera: Danaidae) After Exposure to Permethrin Barrier Treatments. Environ. Entomol. 35(6): 1626-1634.
  • Qualls, W.A., Moser, B.A., Periera, R.M., Xue, R-D, and P.G. Koehler. 2022. Impacts Of Barrier Insecticide Mixtures On Mosquito, Aedes Aegypti And Non-Target Honey Bee, Apis Mellifera.  Journal of the Florida Mosquito Control Association 69: 34-42.

 

 

Medical Entomology, Ticks

The ABCs Of Tick Season In Wisconsin

As weather gets warmer and the outdoors beckons, people across Wisconsin are spending more time with the activities they wait for all winter long, including picnicking, hiking, camping, boating, fishing and more. While thoughts might be turning to filling the cooler with cold beverages and packing enough charcoal for the grill, there’s another aspect to the season that demands attention: tiny ticks and their potential to cause big problems this time of the year.

Wisconsin is home to only a few common tick species, but some pose significant medical concerns to both humans and pets, such as Lyme disease. However, following the ABCs of tick prevention can help ensure that outdoor activities remain fun and safe for family and friends.

    • Avoid: Given their small size, ticks have limited mobility. To find hosts, ticks often hang out on plants — such as tall, weedy grasses along the edges of trails and in wooded areas with dense vegetation — and they wait for a mammal to pass by.  Steering clear of these areas can help reduce the chances of encountering ticks in the first place.
    • Be aware: Become familiar with common ticks and symptoms of tick-borne illnesses to know what to look for. Anybody bitten by a tick should get it properly identified and consult their health care provider about any potential medical concerns.
    • Clothing: Long-sleeved clothes provide a physical barrier to help prevent ticks from getting to skin. Wearing lighter-colored clothing such as khakis can also make it easier to spot darker-colored ticks. Tucking pants into socks can serve as an additional protection to make it harder for ticks to bite.
    • DEET and other repellents: A number of Environmental Protection Agency-approved repellents (such as DEET) can help keep ticks at bay when properly used. Always consult the product label for important usage instructions, such as application to skin versus clothing and how often to reapply. As another consideration, clothing can be treated with repellent products containing permethrin. These products designed for clothing treatments are often sold at outdoor and camping stores and can provide long-term protection from ticks when properly used. Some outdoor clothing brands even use fabrics impregnated with permethrin to provide protection for extended periods of time, even through repeated washings.
    • Examine: Tick checks can be an important precaution for both people and pets. To effectively transmit the bacteria that cause Lyme disease, deer ticks have to be attached and feeding for extended periods of time, usually at least 24 hours. This time requirement for infection means that daily checks can help find and remove ticks before they’ve had a chance to transmit the bacteria. If a tick is found biting a person or pet, the best removal method is to use tweezers to grab near the tick’s mouth parts and use a slow steady pull to remove it.
    • Family pets: Don’t forget about four-legged friends — pets that spend time outdoors can also be affected by tick-borne diseases. Veterinarians should be consulted to select appropriate preventative tick (and flea) products. Topical repellent sprays are also available for those times people take their pets hiking in prime tick habitat. Pay special attention when selecting products for pets, as there are important differences between products available for dogs and cats. Always check with the veterinarian with any questions. For longer term prevention, Lyme disease vaccines for dogs are also available through veterinarians.

More information about ticks and tick-borne diseases is available through the University of Wisconsin-Madison Department of Entomology and the Wisconsin Department of Health Services.

This article was previously published on the Wiscontext website.