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Parawixia bistriata

Parawixia bistriata

Ñandutí
Aranha do Cerrado

Family: Araneidae
Order: Araneae
Class: Arachnida
Phylum / Division: Arthropoda
Kingdom: Animalia

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Synonyms: Eriophora bistriata.





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Records from Santa Fe


Description


Belongs to the family Araneidae and is recognized as one of the few spider taxa that exhibits highly coordinated social behavior. It presents a pronounced sexual dimorphism, with adult females reaching body lengths of 15 to 20 mm, while males are notably smaller, measuring approximately 10 to 12 mm. Its morphology is characterized by a robust, reddish-brown prosoma covered with whitish setae. The opisthosoma is globose, featuring two well-developed humeral tubercles and a distinctive dorsal pattern consisting of two longitudinal light yellow or cream-colored stripes running along the dorsum, flanked by dark brown or grayish tones. Its legs are strong, spiny, and exhibit alternating light and dark bands that give them a highly characteristic brindled appearance under nocturnal light.

Geographical distribution: It is widely distributed across the South American Neotropics. Its presence is solidly documented in countries such as Brazil (particularly in the Cerrado, Pantanal, and fragmented areas of the Atlantic Forest), Paraguay, Uruguay, northern and central Argentina (reaching as far south as the temperate provinces of the Pampean region), and adjacent areas of Bolivia.

Habitat: It primarily inhabits open and semi-open biomes with scattered shrubby and woody vegetation. It is especially abundant in the Cerrado, the wooded savannas of the Chaco, subtropical forest edges, degraded pastures, and human-modified transitional areas, such as commercial forestry plantations, agricultural fence lines, and suburban gardens where it finds suitable structures for anchoring its complex and imposing web networks.

Feeding: It is a generalist and opportunistic insectivorous predator that exploits seasonal prey pulses. Its diet is mainly composed of medium to large flying insects such as beetles, flies, moths, grasshoppers, and hymenopterans. It highly efficiently exploits the massive swarms of winged termites and flying ants during the rainy season, times when the colony can capture thousands of prey items in a single night due to the massive capture surface area of their interconnected webs, which act as large filters in the canopy.

Behavior: It manifests one of the most complex forms of socialization among arachnids, classified as intermediate social or quasisocial. During the day, individuals gather compactly in a communal retreat (bivouac) constructed with dense silk threads, dry leaves, and debris, located on tree branches at a safe height to protect themselves from predators and solar desiccation. At twilight, the colony becomes active in a highly synchronized manner; hundreds of individuals emerge from the bivouac and cooperate in building a colossal three-dimensional support structure from which dozens of individual orb webs hang, which are actively built and defended by each spider. At dawn, they consume their individual orb webs to recycle the silk protein and return in perfect single file to the communal retreat, demonstrating remarkable spatial and temporal coordination.

Reproduction: This biological process is concentrated mainly during the transition between autumn and winter in the Southern Hemisphere. Mating occurs near the communal retreat, where males, abandoning their foraging habits on the web, court females through rhythmic vibrations on the tension threads. After copulation, gravid females deposit their eggs in communal silk egg sacs (cocoons) of cottony texture and yellowish or ocher coloration, which are firmly attached near the bivouac or in cracks in the bark of nearby trees. Each egg sac can contain between 200 and 500 eggs. Adult females die shortly after oviposition, cementing an annual life cycle. The spiderlings emerge in late winter or early spring and remain together in the communal nest, showing mutual social tolerance before dispersing via ballooning or founding new subcolonies.

Conservation status: This species is currently not evaluated (NE) by the International Union for Conservation of Nature (IUCN). However, it is a common and abundant taxon throughout most of its distribution range. Its main local threats stem from habitat loss due to deforestation, the fragmentation of native forests by agricultural expansion, and the indiscriminate use of broad-spectrum insecticides in agricultural fields adjacent to its natural colonies, which drastically reduces its food sources.



Compilation and publication: EcoRegistros – 13/08/2026




Geographic distribution


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Latest feeding records

Feeding on...
GroupSpeciesDateUser
InsectsMacrodactylus sp.09/01/2021Eduardo Beltrocco




Species photographs

Last published photographs

Foto
Photography ID: 462620
  Juvenile

Santa Fe
Santa Fe
Argentina
09/13/2017
Eduardo Beltrocco
Foto
Photography ID: 435376
 
Santa Fe
Santa Fe
Argentina
02/27/2021
Eduardo Beltrocco
Foto
Photography ID: 429291
♂ ♀
  Adult

Santa Fe
Santa Fe
Argentina
01/09/2021
Eduardo Beltrocco
Foto
Photography ID: 424735
  Juvenile

Santa Fe
Santa Fe
Argentina
12/15/2020
Eduardo Beltrocco
Foto
Photography ID: 424723
♂ ♀
  Juvenile

Santa Fe
Santa Fe
Argentina
12/14/2020
Eduardo Beltrocco
Foto
Photography ID: 406330
 
Santa Fe
Santa Fe
Argentina
01/07/2019
Gustavo Fernando Durán
Foto
Photography ID: 190580
  Adult

Santa Fe
Santa Fe
Argentina
02/16/2017
Pablo Capovilla
Foto
Photography ID: 190579
  Adult

Santa Fe
Santa Fe
Argentina
02/16/2017
Pablo Capovilla
Foto
Photography ID: 187137
  Adult

Santa Fe
Santa Fe
Argentina
11/16/2016
Pablo Capovilla
Foto
Photography ID: 128121
  Adult

Santa Fe
Santa Fe
Argentina
05/05/2012
Martin Ferrari
Foto
Photography ID: 68811
  Juvenile

Santa Fe
Santa Fe
Argentina
09/08/2013
Gustavo Fernando Durán
Foto
Photography ID: 63874
  Juvenile

Santa Fe
Santa Fe
Argentina
10/04/2014
Leandro Segovia



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Species reports



 Detail of places sorted by number of records








Page 1
Record IDDateExact timeCountryProvince / departmentPlaceFilmedPhotographedRecorded vocalObservedHeardWounded or deadNumber of individualsUser or BibliographyDetail
236935130/09/202509:08ArgentinaSanta FeReserva Natural Urbana del Oeste, Santa Fe5Gustavo Fernando Durán
204065103/06/2024ArgentinaSanta FeReserva Natural Urbana del Oeste, Santa Fe30Gustavo Fernando Durán
200811414/02/2024ArgentinaSanta FeMuseo y Parque de la Constitución Nacional, Santa Fe1Gustavo Fernando Durán
196771707/02/2024ArgentinaSanta FeReserva Natural Urbana del Oeste, Santa Fe1Gustavo Fernando Durán
190203420/10/2023ArgentinaSanta FeReserva Ecológica Ciudad Universitaria UNL (RECU), Santa Fe20Gustavo Fernando Durán
166402229/10/2022ArgentinaSanta FeReserva Ecológica Ciudad Universitaria UNL (RECU), Santa Fe2Gustavo Fernando Durán
166376128/10/2022ArgentinaSanta FeAvenida de Circunvalación de Santa Fe, Santa Fe50Gustavo Fernando Durán
165495007/10/2022ArgentinaSanta FeParque del Sur "General Manuel Belgrano", Santa Fe50Gustavo Fernando Durán
163403802/09/2022ArgentinaSanta FeParque del Sur "General Manuel Belgrano", Santa Fe70Gustavo Fernando Durán
163039322/08/2022ArgentinaSanta FeParque del Sur "General Manuel Belgrano", Santa Fe120Gustavo Fernando Durán
Page 1

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Recommended citation
Please use the following reference when citing this species account.
EcoRegistros. 2026. Parawixia bistriata – Species account. Accessed from www.ecoregistros.org on 23/09/2026.