Nota 
Note 
On a bite case of Steatoda triangulosa (Walckenaer) (Arachnida: Theridiidae) 
on a human being 
CARVAJAL, Mariom A.1, 2, 3, FAÚNDEZ, Eduardo I.2, 3*, & PEDEMONTE, 
Giuliana G.3, 4 
1 University of Maryland. Entomology Department. 4112 Plant Sciences Building College Park, MD 20742-4454, 
USA. 
2 Smithsonian Institution, National Museum of Natural History. 10th St. & Constitution Ave. NW, Washington, DC  
20560, USA. 
3 Laboratorio de entomología y salud pública, Instituto de la Patagonia, Universidad de Magallanes, Av. Bulnes, 
01855 Punta Arenas, Chile.   
4 SanVicente, Buenos Aires, Argentina. 
*E-mail: ed.faundez@gmail.com. 
 
Received 10 - X - 2022 | Accepted 04 - III - 2023 | Published 31 - III - 2023  
https://doi.org/10.25085/rsea.820111 
Sobre un caso de mordedura de Steatoda triangulosa (Walckenaer) (Arachnida: Theridiidae) 
en un ser humano 
RESUMEN. Se reporta el segundo caso de una mordedura de la “falsa viuda” Steatoda triangulosa 
en un ser humano. El ataque constó de dos mordeduras y ocurrió en San Vicente, Provincia de 
Buenos Aires, Argentina y la víctima es una mujer de 31 años, que se encontraba durmiendo y 
despertó al sentir las molestas y divisar la araña. El caso incluyó síntomas típicos del steatodismo 
como dolor local y radiante, y malestar general por cerca de un día. Adicionalmente se observaron 
eritemas en ambos sitios de las mordeduras que duraron cerca de 10 días, mientras que en el sitio 
de la primera mordedura apareció también un hematoma cuya duración fue de 3 días. Se discuten 
las implicancias de la mordedura en el contexto de las investigaciones actuales sobre steatodismo. 
PALABRAS CLAVE. Aracnidismo. Araña. Especie cosmopolita. Sinantrópico. 
 
ABSTRACT. The second case of a bite by the “triangulate false widow” Steatoda triangulosa is 
reported on a human being. The case occurred in San Vicente, Buenos Aires, Argentina on a 
female 31 years old victim, who woke up felling a nuisance and spotting the spider on her arm. The 
spider inflicted two bites causing typical steatodism symptoms including local and radiating pain 
and malaise which lasted for about a day. In addition, the appearance of an erythema on each bite 
side that lasted about 10 days plus a haematoma in the first bite site which lasted for 3 days. The 
implications of the case in the context of current research in steatodism is discussed. 
KEYWORDS. Arachnidism. Cosmopolitan species. Spider. Synanthropic. 
 
 
Steatoda triangulosa (Walckenaer), commonly known as some cases largely surpass the spider size (Faúndez et 
“triangulate cobweb” or “triangulate false widow”, is a al., 2021; Faúndez & Albornoz, 2017). 
cosmopolitan and synanthropic spider, widely distributed Steatodism, the clinical condition caused by bites of 
in all continents except in the Antarctica (Levi, 1967, spiders in the genus Steatoda, is classically defined as 
Faúndez et al., 2021). This species is well known for causative of radiating pain (median duration 6 h) and 
having a wide range diet, including a variety of arthropods systemic effects (nausea, headache, malaise and 
and some vertebrates (Vitkauskaite et al., 2021), which in lethargy) (Isbister & White, 2004). However, during the 
CARVAJAL, M.A.   88 
CARVAJAL, M.A.et al. On a bite by Steatoda triangulosa 
past couple of years, new case studies have described an The development of the bites was followed and 
increase number of additional symptoms associated with photographed on a daily basis until it receded. Photos 
it, including headaches, nausea, debilitating pain, tremors, were taken with a digital camera. The pain was rated in a 
reduced or elevated blood pressure and fever, range of 1 to 10 scale where 10 is the most painful. The immediate 
duration from 1 to 72 hours (Dunbar et al., 2018, 2020a; symptoms included irritation and local pain (pinprick like), 
Faúndez & Tellez, 2016; Faúndez et al., 2020, 2021). and tingling, during the first half hour (pain 6/10). After that 
More recently, steatodism has been extended to severe the victim fell asleep and woke up five hours later. About 
symptoms that include necrosis and bacterial infections, 30 minutes later, the local initial symptoms disappeared 
updating its status from a mild to a moderate medically completely. At this time there was local pain and itching, 
important condition (Dunbar et al., 2020b, 2021). plus general malaise (including headache, lethargy, 
Most of the reported bites by “false widows” in the general myalgia) (8/10) which persisted for an additional 
literature correspond to S. nobilis and S. grossa (Isbister & 24 hours approximately. Two irregular erythematous 
White, 2004; Dunbar et al., 2020b). In S. triangulosa, only patches appeared in the area of each bite, of 20 mm and 
one case of steatodism has been described from France 15 mm, respectively, with a small wound at the center of 
(Pommier et al., 2006) with the assumption that it was S. each one, presumably in the exact location of the bite. On 
triangulosa. The purpose of this work is to provide a the second day a small haematoma appeared in the 
second case of biting of this species from San Vicente, border of the first bite (Fig. 1B), which lasted for about 
Buenos Aires, Argentina. 5 days (Figs. 1B-C). The erythema remained swollen and 
sensitive the first two days, and started to fade away after 
The bite reported here was exerted by a mature female 3 days since the bite (Fig. 1D) and took 10 days to fully 
specimen of S. triangulosa, and occurred in San Vicente, disappear. The victim did not receive any medical 
Buenos Aires, Argentina, on September 27th, of 2022 treatment and did not have any allergies to arthropod bite-
(Spring in Argentina), around 2:00 AM. When falling history. 
asleep, the victim felt something walking in the right 
forearm. The victim, unconsciously, tried to take off the The female genitalia of the spider was prepared 
arthropod and consequently the spider bit once. A few following the procedure in Carvajal et al. (2022). In 
seconds later, it bit again and left away, upwards towards systematics we followed the World Spider Catalog (2022). 
its web, near the ceiling and the upper side of a window For spider identification we followed Levi (1962, 1967) and 
where it was followed by the victim for its capture and later Faúndez et al. (2021). For terminology of the case we 
identification (Fig. 1A). The victim was a 31 years old followed Isbister & White (2004) and in descriptive format 
woman, in healthy status. The spider perpetrated two bites to Faúndez & Téllez (2016). The specimen was identified 
in the right forearm (Fig. 1 B-D). as S. triangulosa. 
 A recurrent hardship when reporting spider bites is not 
being able to recover or find the specimen that caused it 
and therefore making it impossible to identify. In the 
previously known case by Pommier et al. (2006), the 
authors attribute the bite to S. triangulosa because of the 
clinical signs and the result of a survey in the house of the 
victim, in which S. triangulosa was found to be prevalent. 
However, the specimen that induced the bite is unknown. 
Additionally, this was an area within the distribution of 
Latrodectus tredecimguttatus (Rossi), and symptoms of 
strong steatodism and mild latrodectism can overlap. The 
case presented in this work differs in the sense that the 
victim reacted when detecting the spider walking in her 
arm, followed and captured the specimen, thus allowing its 
taxonomical identification. Therefore, the case presented 
here is the first confirmed case of a bite by S. triangulosa. 
Taking this into consideration, the development of 
steatodism in the presented case is similar to the one 
described by Pommier et al. (2006) including symptoms 
like myalgia, erythema and a local burning sensation. 
However, it differs in that the victim in the previous work 
Fig. 1. Steatoda triangulosa diagnostic characteristics and 
injury caused by the bites. A. Epigynum of the dissected had a history of high blood pressure, which worsened 
female, showing vulva (Scale = 0,5 mm). B. Bites after 3 days during the onset of the symptoms but recovered without 
with haematoma (Scale = 10 mm). C. Bite after 4 days, the aid of additional medications. 
haematoma fading (Scale = 10 mm). D. Bite after 7 days, nearly 
disappearing (Scale = 10 mm). 1 = first bite, 2 = second bite. A peculiarity of the present case was the duration and 
(Photos, G. Pedemonte). timing of the onset of the symptoms. Usually, initial 
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Revista de la Sociedad Entomológica Argentina 82 (1): 88 - 90, 2023 
symptoms of steatodism last up to a couple hours and Dunbar, J.P., Vitkauskaite, A., O’Keeffe, D.T., Fort, A., 
cutaneous lesions recover fully within the week. In this Sulpice, R. & Dugon, M.M. (2021) Bites by the noble 
case we observed that an erythema and swelling false widow spider Steatoda nobilis can induce 
Latrodectus-like symptoms and vector-borne bacterial 
appeared about 48 hours after the bite. This could be 
infections with implications for public health: a case 
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from opportunistic commensals, microbes in the surface of 
Esmaeilishirazifard, E., Usher, L., Trim, C., Denise, H., 
the spider chelicerae or in the venom. This last being a 
Sangal, V., Tyson, G.H., Barlow, A., Redway, K.F., 
new discovery by Esmaeilishirazifard et al. (2022) in which Taylor, J.D., Kremyda-Vlachou, M., Davies, S., Loftus, 
the assumption that venom is sterile is challenged. T.D., Lock, M.M.G., Wright, K., Dalby, A. Snyder, L.A.S. 
Another reason for the extended onset of the symptoms Wuster, W., Trim, S. & Moschos, S.A. (2022) Bacterial 
could be the spider itself, since the specimen that bit was Adaptation to Venom in Snakes and Arachnida. 
a female and female spider venom is known to be stronger Microbiology Spectrum, 10(3), 1-16. 
due to the nutrition requirements related to producing Faúndez, E.I. & Téllez, F. (2016) Primer registro de una 
offspring (Lüddecke et al., 2022). mordedura de Steatoda nobilis (Thorell, 1875) 
(Arachnida: Araneae: Theridiidae) en Chile. Arquivos 
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Faúndez, E.I., & Albornoz, M. (2017) Sobre un registro de 
symptoms reappear after months or years after the bite predación de Steatoda triangulosa (Walckenaer, 
(Pincus et al., 1999; Carvajal & Faúndez, 2018). The 1802)(Araneae: Theridiidae) sobre Tityus trivittatus 
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