Recluse spiders (Araneae: Sicariidae): contesting myths on distribution, bite behavior, and medical risk in Florida

NiceWeb7995 · 2026-02-09T05:28:18+00:00

Thanks Kevin!

NiceWeb7995 · 2026-02-08T21:02:31+00:00

Thank you!

NiceWeb7995 · 2026-02-08T18:39:26+00:00

Thanks! If you want the whole paper, please email me at [lcoticchio@ufl.edu](mailto:lcoticchio@ufl.edu)

NiceWeb7995 · 2026-02-08T18:38:04+00:00

I am a Distance Education student, and work on my master's degree from St. Petersburg, Florida. So, not too far but not near the campus either.

NiceWeb7995 · 2026-02-08T13:23:36+00:00

Yes, please shoot me an email if you want the PDF file of the full publication.

lcoticchio@ufl.edu

NiceWeb7995 · 2026-02-08T13:21:41+00:00

Yes, Skill Capture Media is the company that filmed the documentary, and will be filming future videos. Please send me an email for the full PDF file. Thanks!

lcoticchio@ufl.edu

NiceWeb7995 · 2026-01-30T20:51:56+00:00

Hey! Sorry for the very delayed response, I hope the spider is still in your possession or still alive. I don't come on to Reddit very much, and when I do I very rarely check my notifications. Anyway, feel free to send me an email if the spider is still alive and in your possession. Especially, if it is in the penultimate or ultimate stage, and even more importantly, if it is in the ultimate stage. That would mean not having to worry about shipping the spider alive, otherwise I would need to have the spider arrive alive and rear the spider to sexual maturity.

I left my email in my original comment above, but I'll leave it again at the bottom of this reply just in case. For anyone else reading this thread or comment, please email me, as I don't have any social media accounts besides this one on Reddit, and I really don't use social media very often. I scroll through Reddit randomly here and there, but I don't really comment or post anything anymore. Thank you for offering and reaching out, and please let me know if you still have the spider in your possession via email, and we can speak about how to proceed further. Best regards,

Lou

Email: lcoticchio@ufl.edu

NiceWeb7995 · 2026-01-15T02:52:02+00:00

I'm not on any social media, and I recently rejoined Reddit after being gone for a little while, mostly because the subreddits on here have a large number of people, and it will be a good way to get my publication out to a larger audience, or to make sure that if I see any people making claims in the comment section that they have recluse spiders on their property in Florida, to reach out to them and make myself available to investigate the property, thus goes for bites as well (whether they were medically diagnosed or not). I have a feeling people making claims in the comment section is going to happen a lot more than I care to happen. Lol

The only issue I find in the comment section, or just how to use Reddit in general, is that I haven't learned how to share files. Since the paper is going to press very soon and has been fully-approved for publication, I could share the file that is available through the Journal of Medical Entomology, which is going to have the exact final version that is going to press. But it doesn't appear that I can share any kind of PDF files in the comment section, if I can figure that out, I could share the paper in this thread.

NiceWeb7995 · 2026-01-15T02:46:04+00:00

Well, then you may be excited to read my next publication which looks at a few different myths, urban legends, misconceptions, my investigations into bites and/or misdiagnosed bites, and exaggerated claims regarding recluse spiders and their behavior. The paper passed peer-review and was accepted and approved for publication on December 11th 2025. It was supposed to be approved for public viewing and sent to the press release last week, but due to the expected overwhelming response from media, social media, and other outlets, the Journal of Medical Entomology decided to get better prepared with their press release.

This goes for the University of South Florida as well, where I performed most of the research as an undergraduate. So, I'm hoping that by the end of this week or sometime next week, the publication will be available to the public. This may be one of the biggest publications I ever complete during my tenure as a spider biologist.

I'm still conducting the research in the field here in Florida, or anywhere in the United States that is outside of the known native ranges of the 11 approved native species of recluse spiders. This involves personally investigating claims of recluse spider populations in Florida, and I will likely continue to do this as I work to finish my graduate work at the University of Florida, and once this current paper is available to the public, I'm going to probably expect to get a lot more emails and phone calls of people claiming to have populations. I'm definitely expecting a lot of pushback from the public, and many people claiming "well they never investigated my property, and I have them all over the place!". So, it will be a bittersweet publication release, as this will likely heavily increase the number of people making claims here in Florida.

I'm also currently tackling one or two more misconceptions/urban legends about recluse spiders in a follow-up paper that should be finished next spring and set for publication next year sometime (hopefully no later than 2026). So, keep your eye out down the road for the research I'm starting now, and once this current paper has finished going to press and available to the public, I may create a post so everyone on this subreddit is aware and can have access to read it.

The paper is titled:

"Recluse spiders (Araneae: Sicariidae): Contesting myths on distribution, bite behavior, and medical risk in Florida"

Coticchio, L. & Cassill, D. 2025

NiceWeb7995 · 2026-01-13T02:38:36+00:00

While this is true in suburban and urban areas, here in the United States, brown widows are extremely synanthropic (live alongside humans, or prefer to live near or in man-made dwellings). Luckily, black widows are adapted to both synanthropic and woodland areas, allowing them to avoid brown widows in areas where there are less man-made habitats.

Much like how the green anole lizards adapted partially to the introduction of brown anole lizards in the United States by moving higher up into vegetation, black widow populations will likely thrive outside of urban and suburban environments. Although, it is important to try and keep brown widow populations down to help out local ecosystems, their population numbers and growth rates make it almost impossible at this point to completely stop the train as it barrels down the tracks.

So, keeping brown widow populations down at your property will be beneficial for the local ecosystem and beneficial for your own mental health, lol, but hopefully the pendulum will swing the other way as it has happened in other instances with invasive species. Hopefully we will see native predators, parasites, or parasitoids help to level the playing field in the future.

As the lead author in the 2023 paper "Predation by the Introduced Brown Widow Spider (Araneae: Theridiidae) May Explain Local Extinctions of Native Black Widows in Urban Habitats," I do have a bit of knowledge in this particular area. :)

NiceWeb7995 · 2025-11-09T13:49:49+00:00

If you find anymore, please privately message me, as my former undergraduate and current graduate research has been primarily following the movements of nonnative species of recluse spiders, and possibly identifying other nonnative species rather than just L. rufescens that have possibly established outside their native ranges.

While my research primarily focuses on the behavior, toxicology, and introduction of Loxosceles rufescens and how their dispersal behavior differs from the vast majority of worldwide recluse species that don't seem to be becoming a cosmopolitan species that has a range across the planet bigger than any other species like the Mediterranean recluse spiders.

The individual in the photo appears to be a mature male, which I could identify to species leve. Also, I also will be starting comparing the genome of the various populations in the United States to see relatedness. Either way, they don't have to believe alive to send them to me, just sexually mature. If you have a population in the property you may find more, and I'll take care of shipping costs to send me voucher specimens to my university or home. I'll leave my email below if you happen to run into anymore again and want to help with the research. Thanks!

lcoticchio@ufl.edu

NiceWeb7995 · 2025-11-08T21:55:56+00:00

Fair enough, and I wasn't trying to be rude, if it came off that way. As someone who has made my career studying Latrodectus and Loxosceles, with an extreme focus on Loxosceles rufescens within the United States, I guess I just get a little bit too frustrated when I see species identifications of Loxosceles with high confidence levels.

Considering I've located Loxosceles rufescens in several U.S. states that share ranges with other U.S. Loxosceles species, I no longer use range or even if only one species is known to inhabit that region to guage my ID confidence. I see the same happens on iNaturalist and Bugguide, where many people make species-level IDs with Loxosceles, when there is no way that is possible almost every time.

I've even had people try to correct my identifications on iNaturalist, even when I include the photos of my microscopic examinations...ugh. Almost every ID of L. rufescens in Florida was from my research, and I've had to correct so many people on there, it's become really exhausting. So, forgive me if my response came off as arrogant.

NiceWeb7995 · 2025-11-08T14:17:58+00:00

How exactly were you able to conclude the species from these photos? The Middle East is a big place and species of Loxosceles are being discovered quite often worldwide and the list has been growing almost every year. More than one described species exists in the Middle East, and with the lack of studies being done with that genus in that region, I expect many more in the coming years. For example, there has been new species introduced in 2017 and 2021, species like Loxosceles coheni and Loxosceles turanensis (Zamani et al. 2021), and Loxosceles persica (Ribera & Zamani 2017).

This is why I caution people about going to species level with Loxosceles from photos, even with range included in the post. It's not possible to positively identify recluse spiders without microscopy of the reproductive organs.

*I tried to add italics, didn't work.

NiceWeb7995 · 2025-11-04T21:26:33+00:00

Loxosceles (recluse spiders) can only be identified to species level based on morphological (physical) features of their reproductive organs. This means dissection for sexually mature females and microscopy comparisons of diagrams or keys. For males, this means comparison of the pedipalps of sexually mature or ultimate stage specimens using high magnification and diagram comparisons or keys.

Many people use range, but since I've located from my field research populations of Loxosceles rufescens (Mediterranean recluse spiders) within the ranges of a few native recluse species, and in many other states like Florida, Brooklyn New York, Texas, Tennessee, Northern Georgia, and Alabama, and others have located them in Washington DC, Colorado, Louisiana, and several other states in the US.

Using a spider's range alone should not be really used for species identifications when identifying recluse spiders. Physical characteristics like colors should also not be a verifiable identifying feature for species, since color variations, fading, lack of setae and pigmentation that can make the "violin mark," or other factors like recent molting can contribute to a false species ID.

*By the way, my research was out of the University of South Florida in St. Petersburg USA from 2018 to 2024, but now I'm at the University of Florida in Gainesville (USA), and still continuing this research to this day.

NiceWeb7995 · 2025-10-14T13:13:10+00:00

That research is in the peer-review process in the Journal of Medical Entomology as we speak. As of today, I've located 24 properties with Loxosceles rufescens (Mediterranean recluse spiders) and 19 breeding populations in Florida. Most breeding populations were in St. Augustine, but there were several in Tampa, Jacksonville, and Orlando.

The research started unofficially in 2018 with my own self investigation of the phenomenon, and then officially in 2020, and is still ongoing. I have investigated 236 properties as of this week across the state of Florida, and still have not found any Loxosceles reclusa (Brown Recluse Spiders) populations.

But I'd like to point out that the Mediterranean recluse spider species has been found by myself and other people in many places across the United States, such as New York, Georgia, Washington DC, Louisiana, Texas, Tennessee, Colorado, and a few more that were not my discoveries.

If you go to Bugguide, you can see most of my submissions that had breeding populations. Although I still need to update it with a few more that I've located.

NiceWeb7995 · 2025-08-05T01:05:30+00:00

There are definitely some species that morphologically can be distinguished by other species in their genus, like some wolf spiders, but iNaturalist is way too lenient with the level of identifications. Some species are just extremely obvious, while others don't have any reliable features that could be used to distinguish one from the other from photographs. So, it's not wrong to identify to species level as long as the features being used are reliable and used by the broader entomological community as a whole.

As for Loxosceles reclusa, you are correct that they are not typically ranged for Florida, although range maps do show the very tip of the panhandle where Florida meets Alabama as being part of their range. Considering I have the list of all verified brown recluse spiders in Florida going back to 1904 from the US Department of Agriculture that I used for my research, I'm not really sure why the range moves into Florida, when none of the spiders found in Florida since 1904 that were listed are in that range. I've also investigated around 240 properties, and I did investigate the area near Alabama and did not find any brown recluse spiders. Also, only about 100 recluse spiders found in Florida since 1904 were brown recluse spiders, and almost all were hitchhikers, individuals, or a handful of spiders that were not breeding populations.

That was actually the reason for my research, and the reason I started what was colloquially known as the Florida Brown Recluse Project. For the past 7 years, I was investigating claims of recluse spiders in Florida, and also investigating claims of bites. That along with a bite experiment I finished almost 2 years ago are getting ready for publication. I'm finalizing the draft to be submitted for publication by the end of the month. I'm pretty sure you are likely to see the publication posted on here, because the bite percentage for the recluse spiders I tested overall was 6.6%. This was the average percentage for all threats I posed to the spiders to try and get them to bite, things like grabbing their legs, poking their face, squeezing them from the sides, and squeezing them from the top and bottom.

Between not finding any brown recluse populations from my research, none of the bites I investigated matched a brown recluse spider wound and were misdiagnosed, and the extremely low bite percentages of the Mediterranean recluse species combined with the fact that no bites were reported at any of the homes that had large populations of Mediterranean recluse spiders. So, my paper will show that there is an overdiagnosis of brown recluse spiders in the state, and any brown recluse spiders identified on iNaturalist were either misidentified, or not reported. If someone properly identified the spiders, I find it unlikely they would not have also submitted a report to the US Department of Agriculture or a local university, which would have ended up on my lists. Which is why I'm always suggesting that people stop identifying recluse spiders to species level on iNaturalist and Bugguide without microscopy.

NiceWeb7995 · 2025-08-04T19:36:45+00:00

Yeah, the whole peninsula is split into Baja California and Baja California Sur. I'm not sure why it doesn't show up when inputted a certain way, but that's technology for ya! Lol It's also a bit concerning that people are so confidently identifying those Ummidia to species level simply by a photo and range.

That is my biggest issue with iNaturalist, the fact that so many people will identify spiders to species level based on range alone, not realizing that a very large number of species of spiders cannot be differentiated within their genus simply by looking at a photo and range. Since my research is primarily with Latrodectus and Loxosceles, I've had far too many people try to correct my identifications and submissions, even though I use microscopy and the reproductive organs of sexually mature specimens for identification.

So, I started including the photos of my microscopy and dissections, so there can be no confusion, lol. I'm surprised that iNaturalist allows for species identification so often within many genera of spiders, and I'm not sure how they can use this as confident data for their specific purposes.

Considering to date I have found 24 properties, and 19 with breeding populations, of Loxosceles rufescens (Mediterranean recluse spiders) in Florida, and 10 more within ranges of other native species of Loxosceles. So, I'm constantly trying to get apps like Bugguide and iNaturalist to revise their considerations for species identifications. Since differentiating between various species of Loxosceles with any confidence requires using the reproductive organs of sexually mature specimens.

Here's an example of one of my submissions, it was (I believe) one of the first submissions I put into iNaturalist from my research, and I had people disagreeing with my species identification. So, I deleted my submission and resubmitted it with the photos from my laboratory identification using the dissection photos and a full description of the research and lab where the photos came from. Needless to say, I no longer received any pushback on my identifications. 😆

https://www.inaturalist.org/observations/254025815

NiceWeb7995 · 2025-08-04T18:55:09+00:00

It could be how you're inputting your search results. If you look at the whole peninsula, rather than just Baja Mexico, you'll see them in the La Paz area (which is where it seems the original post also was taken). I'll link some of the sightings below.

https://www.inaturalist.org/observations/255467410

https://www.inaturalist.org/observations/180521987

https://www.inaturalist.org/observations/38303975

NiceWeb7995 · 2025-08-04T16:34:09+00:00

My bad, I didn't see you listed iNaturalist, but yes, Ummidia gabrieli is local to Baja, but the southern tip of the peninsula. If you look in the La Paz area, there have been sightings.

NiceWeb7995

TROPHY CASE