Anelosimus eximius

Geographic Range

Anelosimus eximius is a social spider found in the Neotropical region, specifically in Central and South America. In particular, it inhabits as far north as Panama and then sthrough eastern Ecuador to Peru. This spider is found patchily in locations such as Suriname as well as eastern and southern Brazil. Colonies can also be found on islands such as Trinidad and the Lesser Antilles. (Smith, 1986; Vollrath, 1986)


Anelosimus eximius is found in the lowland rainforest. In particular, this social spider is found in the interior forest floor and forest edge. Therefore this species of spider is rarely ever found in the canopy levels of the rain forest. Typically, they are found in cleared areas or around tree falls. The webs can be found as low as a meter off the ground to 20 meters in the canopy.

Colonies can be found from 30 meters to 880 meters above sea level. Anelosimus eximius colonies decrease in web area size altitude decreases. According to Volrath (1986), this is due to seasons generally being harsher at lower altitudes and damaging the webs. (Majer, et al., 2013; Smith, 1986; Vollrath, 1986)

  • Range elevation
    30 to 880 m
    98.43 to 2887.14 ft

Physical Description

Female Anelosimus eximius size can range from 4.4 to 6 millimeters. Guevara and Aviles (2011) report the female weight ranges from 2.55 to 11.82 mg. Females are reported to be larger in weight and length than males although no specific measurements have been published for males. The size and weight of juvenile spiders have not yet been recorded in any published studies. (Guevara and Aviles, 2011)

  • Sexual Dimorphism
  • female larger
  • Range mass
    0.00255 to 0.01182 g
    0.00 to 0.00 oz
  • Range length
    4.4 to 6 mm
    0.17 to 0.24 in


The social spider, like other arachnids, begins as an egg. Here in this first stage, the spider goes through its first molt. The incubation period within the egg sac is 20 to 30 days. After the first molt the spiders emerge from the egg sacs. After emerging the social spiders then go through 5 to 6 developmental stages, depending on sex. Each time period in between molts is numbered as an instar, or stage. The third instar is when the spiders begin to take part in colony duties. The males reach reproductive maturity in their 5th instar while females reach reproductive maturity in their 6th instar. Reaching these maturity stages can take up to 2 to 3 months. (Aviles, 1986; Aviles, 1997; Breene, 2014; Vollrath, 1986)


Males can attract females through patterned vibrations with the strings that make up their web, as well as visual cues, such as swaying of the legs. In addition males can lay down a scent of pheromones on a line of thread to direct the female towards them. In some cases, the males use both methods of vibration and pheromone communication.

In most cases males seek out the female because the females stay with the nest to invest in the web and eggs. This social spider is considered polygynandrous. (Aviles, 1986; Krafft and Cookson, 2012; Vollrath, 1986)

The breeding season of Anelosimus eximius is aseasonal, meaning the spiders do not have a particular season. Furthermore, the social spider can breed more than once in its life span. Depending on the resource factor, such as food, each egg sac can carry 17 to 53 eggs. The eggs hatch after an incubation period of 20 to 30 days.

Females reach maturity in the 6th instar while males mature in the 5th instar. When spiders reach their 3rd instar they become involved in colony tasks, such as hunting, maintenance, and mating. (Aviles and Tufino, 1998; Aviles, 1997; Vollrath, 1985)

  • Breeding interval
    Anelosimus eximius breed aseasonally and randomly.
  • Breeding season
    The spider's courtship and mating is random
  • Range number of offspring
    17 to 53
  • Range gestation period
    20 to 30 days
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    2 to 3 months
  • Range age at sexual or reproductive maturity (male)
    2 to 3 months

Aviles (1986) suggests that both parents invest an equal amount in the offspring. However, according to Vollrath (1985), females invest significantly more into the young. Vollrath says the males contribute little to nothing beyond the mating process.

The spiderlings are cared for by the female until the 3rd instar. The female protects, feeds, and hunts for the young. The adult social spiders invest in the spiderlings until they can interact in colony duties. (Aviles, 1986; Vollrath, 1985)


According to Avilés (1986), female spiders have an average life span of 76 ± 13 days while males have an average of 71 ± 13 days. The maximum lifespan of sexes are close in range. A single female was reported to have lived 94 -103 days in the wild, while there are recordings of three males living 103 ± 13 days in the wild. These spiders are not kept in captivity. (Aviles, 1986)

  • Range lifespan
    Status: wild
    90 to 116 days
  • Average lifespan
    Status: wild
    71 days
  • Typical lifespan
    Status: wild
    94 to 103 days
  • Average lifespan
    Status: wild
    71 days


Being called a social spider, Anelosimus eximius is colonial. Colonies consist of thousands of spiders.

These particular social spiders perform tasks that are shared through the colony. The tasks include web maintenance and construction, brood care, defenses, along with attacking prey for when insects hit their trap. Furthermore, the spiders cooperate when capturing the trapped insects. According to Settepani et al. (2013), these tasks are often separated by age and sex. Females after the third instar are more likely to perform the colony tasks as well as hunt. Researchers believe Anelosimus eximius performs these tasks to be more efficient in the idea of maintaining a successful colony.

The social spiders are sedentary. Emigration is very rare. However, according to Smith and Hagen (1996), when the spiders do relocate it occurs when the nests are by the roadside. This may be due to the nests being more open or vulnerable to trucks driving or having less cover from the weather. (Agnarrson, 2005; Kim, et al., 2005; Powers and Aviles, 2007; Settepani, et al., 2013; Smith and Hagen, 1996)

  • Range territory size
    20 to 28 m^2

Home Range

Home range and territory size is the size of their web. Rarely, does Anelosimus eximius travel out of its own web. Therefore its home range is a 3-D area with the range of volume from 0.0001 to 1,000 meters cubed.

Nentwig (1985) records area of the social spiders' webs being from 20 to 28 meters squared. (Krafft and Cookson, 2012; Nentwig, 1985; Smith, 1986)

Communication and Perception

According to Vakanas and Bertrand (2001) and Kraft and Cookson (2012), there is no observable direct communication between the spiders. However, there does appear to be organization and cooperation, leading to the ability to catch larger prey. The spiders appear to adjust their behavior to match the situation or the prey.

In terms of perception, these social spiders perceive their surroundings through their web. The span of their web acts as a visual perception of depth of their environment.

Likewise, the web is also used for communication. Anelosimus eximius utilizes the strings by vibration of the legs and abdomen to communicate with another spider. In addition, they can also communicate through attaching pheromones to threads for sexual communication. (Krafft and Cookson, 2012; Vakanas and Bertrand, 2001)

Food Habits

Anelosimus eximius creates its web to act as a net trap. Above their main net they have a vertical non-stick web. This part acts as a net to trap and cause insects to fall into a bowl shaped nest below to be bombarded by the thousands of spiders (Vollrath, 1986). Although they are small organisms this technique allows them to catch much larger prey. Reported by Nentwig (1994), the diet of Anelosimus eximius was studied in two sites. The first was Cerro Galera, Panama where their prey-capture made up of 19.9% of Formicoidea (ants), 17.8% of Coleoptera (beetles), 17.2% of Heteroptera (true bugs), and 12.7% of Blattodea (roaches). The second was El Valle, Panama where their diet composed of 9.1% of Formicoidea, 35.0% of Coleoptera, 10.6% of Heteroptera, and 10.6% of Blattodea. the authors concluded that the spiders are consuming these groups in larger percentages than what is naturally available. (Nentwig, 1985; Vollrath, 1986)

  • Animal Foods
  • insects


There are no known natural predators recorded.

Ecosystem Roles

Within the ecosystem of Anelosimus eximius, the spider has kleptoparasites that thrive within their web. These are organisms that are also referred to as food stealers. The social spiders' main kleptoparaiste is Argyrodes ululans. These are smaller spiders that steal prey that is around 11mm in size from Anelosimus eximius. According to Cangialosi (1990) due to the parasitic spiders, the social spiders can lose up to 26% of their food resource. Consequently, the social spiders address this problem through avoiding, tolerating, and fighting off the kleptoparasites. (Cangialosi, 1990)

Commensal/Parasitic Species
  • spider Argyrodes ululans

Economic Importance for Humans: Positive

There are no known positive economic effects of Anelosimus eximius on humans.

Economic Importance for Humans: Negative

There are no known negative economic effects of Anelosimus eximius on humans.

Conservation Status

The conservation status of this spider has not yet been reported. This spider is not recognized by the IUCN Red List, is not protected by CITES, and is not federally or state listed. Because no scientific publications suggest its populations are in peril, no conservation measures are currently in place. ("IUCN Red List", 2014)


Skyler Carrell (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University.



living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


chemicals released into air or water that are detected by and responded to by other animals of the same species


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


2014. "IUCN Red List" (On-line). Accessed March 23, 2015 at

Agnarrson, I. 2005. A revision of the New World eximius lineage of Anelosimus (Araneae, Theridiidae) and a phylogenetic analysis using worldwide exemplars. Zoological Journal of the Linnean Society, 146/4: 553-593.

Aviles, L. 1997. Causes and consequences of cooperation and permanent-sociality in spiders. The Evolution of Social Behavioral in Insects and Arachnids: 476-498.

Aviles, L. 1986. Sex-ratio bias and possible group selection in the social spider Anelosimus eximius. The American Naturalist, 128/1: 1-12.

Aviles, L., W. Maddison. 1991. When is the sex ratio biased in social spiders?: Chromosome studies of embryos and male meiosis in anelosimus species (Araneae, Therididae). The Journal of Arachnology, 19/2: 126-135.

Aviles, L., P. Tufino. 1998. Colony size and individual fitness in the social spider Anelosimus eximius. The American Naturalist, 152/3: 403-418.

Breene, R. 2014. "Arachnid Developmental Stages: Current Terminology" (On-line). Welcome to The American Tarantula Society Headquarters. Accessed March 01, 2015 at

Cangialosi, K. 1990. Social spider defense against kleptoparasitism. Behavioral Ecology and Sociobiology, 27/1: 49-54.

Ebert, D. 1998. Behavioral asymmetry in relation to body weight and hunger in the tropical social spider Anelosimus eximius (Araneae, Theridiidae). Journal of Arachnology, 25: 70-80.

Fowler, H., E. Venticinque. 1996. Interference competition and scavenging by crematogaster ants (Hymenoptera: Formicidae) associated with the webs of the social spider Anelosimus eximius (Araneae: Theridiidae) in the Central Amazon. Journal of Kansas Entomological Society, 69/3: 267-269.

Guevara, J., L. Aviles. 2011. Influence of body size and level of cooperation on the prey capture efficiency of two sympatric social spiders exhibiting an included niche pattern. Functional Ecology, 25/4: 859-867.

Kim, K., K. Bertrand, J. Choe. 2005. Cooperative prey capture by young subsocial spiders: II. Behavioral mechanism. Behavioral Ecology and Sociobiology, 59/1: 101-107.

Krafft, B., L. Cookson. 2012. The Role of silk in the behaviour and sociality of spiders. Journal of Entomology, 2012: 1-25.

Laurence, W. 2002. Hyperdynamism in fragmented habitats. Vegetation Science, 13/4: 595-602.

Majer, M., I. Agnarsson, J. Scenning, J. Bilde. 2013. Social spiders of the genus Anelosimus occur in wetter, more productive environments than non-social species. Naturwissenschaften, 100/11: 1031-1040.

Nentwig, W. 1985. Social spiders catch larger prey: A study of Anelosimus eximius (Araneae: Theridiidae. Behavioral Ecology and Sociobiology, 17/1: 79-85.

Powers, K., L. Aviles. 2007. The role of prey size and abundance in the geographical distribution of spider sociality. Animal Ecology, 76/5: 995-1003.

Saffre, F., A. Mailleux, J. Deneubourg. 2000. Exploratory recruitment plasticity in a social spider (Anelosimus eximius). Journal of Theoretical Biology, 205/1: 37-46.

Salomon, M., D. Mayntz, Y. Lubin. 2008. Colony nutrition skews reproduction in a social spider. Behavioral Ecology, 19/3: 605-611.

Settepani, V., L. Grinsted, J. Granfeldt, J. Jensen, T. Bilde. 2013. Task specialization in two social spiders, Stegodyphus sarasinorum (Eresidae) and Anelosimus eximius (Theridiidae). Journal of Evolutionary Biology, 26/1: 51-62.

Smith, D. 1986. Population genetics of Anelosimus eximius (Araneae, Theridiidae). Arachnology, 14/2: 201-217.

Smith, D., R. Hagen. 1996. Population structure and interdemic selection in the cooperative spider Anelosimus eximius. Journal of Evolutionary Biology, 9/1: 589-608.

Vakanas, G., K. Bertrand. 2001. Coordination of behavioral sequences between individuals during prey capture in a social spider, Anelosimus eximius. Journal of Insect Behavior, 14/6: 777-798.

Vollrath, F. 1986. Environment, reproduction and the sex ratio of the social spider Anelosimus eximius (Araneae, Theridiidae). Journal of Arachnology, 14/2: 267-281.

Vollrath, F. 1985. Eusociality and extraordinary sex ratios in the spider Anelosimus eximius (Araneae: Theridiidae. Behavioral Ecology and Sociobiology, 18/4: 283-287.

Yip, E., L. Rayor. 2013. The influence of siblings on body condition in a social spider: Is prey sharing cooperation or competition?. Animal Behavior, 85/6: 1161-1168.