Social spider
Encyclopedia
A social spider is a spider
species whose individuals form relatively long-lasting aggregations
. Whereas most spiders are solitary and even aggressive toward conspecifics
, some hundreds of species in several families show a tendency to live in groups, often referred to as colonies, and continue to provoke the curiosity of naturalists.
, of which there are six defined. Agnarsson et al. estimate that spiders as a whole have independently evolved sociality 18 or 19 times. Most of these social spiders broadly fit into the quasi-social definition of sociality, meaning they show cooperative brood care, use the same nest (web), and have some amount of generational overlap. Several permutations of social behavior exist amongst the 23 species of spider considered to be quasi-social out of some 39,000 known species of spider . These 23 species are phylogenetically
scattered in 11 genera across eight widely separated families. The level of sociality often varies between species (interspecies) but can vary within a species (intraspecies) as well. Intraspecific variation is generally habitat dependant, where some populations within a species show all the characteristics of quasi-sociality, yet a population a mile away may be largely solitary because they inhabit a different environment. This facultative sociality allows them to survive periods of sub-optimal conditions, when sustaining large aggregations is not feasible.
Some of these aggregations can contain as many as 50,000 individuals as in the case of Anelosimus
eximius
(in the family
Theridiidae
). The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar
are at least somewhat social. Members of other species in the same family but several different genera have independently
developed social behavior. For example, although Theridion
nigroannulatum belongs to a genus
with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella
species (family Uloboridae), Agelena
consociata
(family Agelenidae) and Mallos
gregalis
(family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous
spider Bagheera kiplingi
lives in small colonies which helps to protect eggs and spiderlings. Even widow spider
s (genus Latrodectus), which are notoriously aggressive and cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.
A few species, such as Anelosimus
eximius
, are also known to exhibit reproductive division of labor. Some biologists argue that this classifies these species as fully eusocial as these non-reproductives can be considered a non-sterile worker caste. This reproductive division of labor is a result of resource availability and monopolization of those resources. It is believed that certain female individuals will opportunistically gain a head start as juveniles by securing more prey than their peers, allowing for faster growth and larger size. In spiders, dominance is directly proportional to size, and thus with their larger size these spiders are able to monopolize prey items for themselves and further enlarge the size differential between them and the now subordinate spiders. The dominant females are better capable of producing progeny
and also more capable of monopolizing male suitors and eating them after copulation. This process creates a social dichotomy consisting of reproductive dominant females and largely non-reproductive subordinate females which still care for the dominant females’ broods.
Many more species of spider are considered to be sub-social than quasi-social meaning they lack fixed or complex social organization. These species may only display social behaviors as a seasonal venture and have an obligate solitary phase. Some other species will establish territories within the colony and can even have discrete webs, narrowly connected to other webs within the colony. This is not a fully cooperative behavior as there is little to no cooperative nest maintenance or brood care occurring. The subsocial species, however, appear to be crucial for the evolution of sociality in spiders. Recent theory suggests that social spiders evolved along a restricted pathway through solitary subsocial ancestors. It has been shown that the subsocial spiders of genus Stegodyphus tolerate a low level of inbreeding with low inbreeding depression, suggesting a possible stepping stone towards the fully inbred mating system found in social spiders.
Several social spiders including Achaearanea
wau and Anelosimus
eximius
also swarm in an analogous way to the eusocial ants, bees and wasps
. These species disperse and establish new colonies by means of synchronized emigrations of adult and sub-adult females. After courtship and copulation, but prior to oviposition, many females will emigrate to a new nesting site and deposit their eggs, forming a new colony. In this way social spiders are also extremely inbred, as there is limited migration of males or juveniles to different colonies, forcing the offspring to mate with one another decreasing genetic variation within the colonies. Occasionally males will emigrate with females or will emigrate from one colony to another but this is a rare event and has not been studied sufficiently to quantify for any social spider species. Females can also out-number males as much as 10:1 in many species; this too acts as a genetic bottleneck and further decreases the genetic variation of the species.
Most species of social spiders live in the tropical regions of the world where insect size and density is highest but several species reach into the eastern United States and other temperate areas. By building a communal web, it is thought that the spiders approximately maximize total biomass capture per spider. Having a larger web and multiple spiders to work together to subdue prey allows them to prey on larger organisms that would be impossible if they led a solitary existence. The colonies can grow large enough to take down birds and bats as well as very large insects.
Living in a colony also has another major benefit for spiders: cooperative nest maintenance. Nest maintenance does not rely solely on an individual in a colony setting and thus saves on a per-capita investment in maintaining silk structures. Predator defense is also increased in a colony with a large web and multiple individuals analogous to schools of fish or herds of mammals.
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
species whose individuals form relatively long-lasting aggregations
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...
. Whereas most spiders are solitary and even aggressive toward conspecifics
Conspecificity
Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....
, some hundreds of species in several families show a tendency to live in groups, often referred to as colonies, and continue to provoke the curiosity of naturalists.
Spider Sociality
Social spiders exhibit varying levels of socialityEusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
, of which there are six defined. Agnarsson et al. estimate that spiders as a whole have independently evolved sociality 18 or 19 times. Most of these social spiders broadly fit into the quasi-social definition of sociality, meaning they show cooperative brood care, use the same nest (web), and have some amount of generational overlap. Several permutations of social behavior exist amongst the 23 species of spider considered to be quasi-social out of some 39,000 known species of spider . These 23 species are phylogenetically
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
scattered in 11 genera across eight widely separated families. The level of sociality often varies between species (interspecies) but can vary within a species (intraspecies) as well. Intraspecific variation is generally habitat dependant, where some populations within a species show all the characteristics of quasi-sociality, yet a population a mile away may be largely solitary because they inhabit a different environment. This facultative sociality allows them to survive periods of sub-optimal conditions, when sustaining large aggregations is not feasible.
Some of these aggregations can contain as many as 50,000 individuals as in the case of Anelosimus
Anelosimus
Anelosimus is a genus of tangle web spider described by Eugène Simon, in 1891, from Venezuela. It includes the South American social spider Anelosimus eximius and related species....
eximius
Anelosimus eximius
Anelosimus eximius is species of social spider in the genus Anelosimus, native to the Lesser Antilles and the area from Panama to Argentina. Colonies can comprise several thousand individuals....
(in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Theridiidae
Theridiidae
Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
). The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
are at least somewhat social. Members of other species in the same family but several different genera have independently
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
developed social behavior. For example, although Theridion
Theridion
The spider genus Theridion, after which the family Theridiidae is named, consists of almost 600 described species that occur all around the world....
nigroannulatum belongs to a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella
Philoponella
Philoponella is a genus of uloborid spiders. Like all Uloboridae, these species have no venom.The species P. vicinus uses its silk to crush its victims to death.-Cooperation:...
species (family Uloboridae), Agelena
Agelena
Agelena is a genus of Agelenid spiders that trap their prey by weaving entangling non-sticky funnel webs. The genus is limited to the Old world, where it occurs from Africa to Japan...
consociata
Agelena consociata
Agelena consociata is a social species of funnel web spider that occurs in tropical forests in West Africa and lives in colonies of one to several hundred individuals.-Distribution:This species is found in rainforest habitats in Gabon...
(family Agelenidae) and Mallos
Mallos (spider)
Mallos is a spider genus belonging to the Dictynidae family.Among the genus, Mallos gregalis is known to be a social spider species, living in groups and signaling each others by vibrating their web.-External links:*...
gregalis
Mallos gregalis
Mallos gregalis is a spider species belonging to the Dictynidae family.It is known to be a social spider species, living in groups and signaling each others by vibrating their web....
(family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
spider Bagheera kiplingi
Bagheera kiplingi
Bagheera kiplingi is a species of jumping spider found in Central America including Mexico, Costa Rica and Guatemala. It is the type species of the genus Bagheera, which includes one other species, B. prosper. B. kiplingi is notable for its peculiar diet, which, uniquely for a spider, is mostly...
lives in small colonies which helps to protect eggs and spiderlings. Even widow spider
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
s (genus Latrodectus), which are notoriously aggressive and cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.
A few species, such as Anelosimus
Anelosimus
Anelosimus is a genus of tangle web spider described by Eugène Simon, in 1891, from Venezuela. It includes the South American social spider Anelosimus eximius and related species....
eximius
Anelosimus eximius
Anelosimus eximius is species of social spider in the genus Anelosimus, native to the Lesser Antilles and the area from Panama to Argentina. Colonies can comprise several thousand individuals....
, are also known to exhibit reproductive division of labor. Some biologists argue that this classifies these species as fully eusocial as these non-reproductives can be considered a non-sterile worker caste. This reproductive division of labor is a result of resource availability and monopolization of those resources. It is believed that certain female individuals will opportunistically gain a head start as juveniles by securing more prey than their peers, allowing for faster growth and larger size. In spiders, dominance is directly proportional to size, and thus with their larger size these spiders are able to monopolize prey items for themselves and further enlarge the size differential between them and the now subordinate spiders. The dominant females are better capable of producing progeny
Progeny
Progeny can refer to:*A genetic descendant or offspring*An academic progeny Other uses*Progeny Linux Systems*Progeny - an episode of the television series Stargate Atlantis...
and also more capable of monopolizing male suitors and eating them after copulation. This process creates a social dichotomy consisting of reproductive dominant females and largely non-reproductive subordinate females which still care for the dominant females’ broods.
Many more species of spider are considered to be sub-social than quasi-social meaning they lack fixed or complex social organization. These species may only display social behaviors as a seasonal venture and have an obligate solitary phase. Some other species will establish territories within the colony and can even have discrete webs, narrowly connected to other webs within the colony. This is not a fully cooperative behavior as there is little to no cooperative nest maintenance or brood care occurring. The subsocial species, however, appear to be crucial for the evolution of sociality in spiders. Recent theory suggests that social spiders evolved along a restricted pathway through solitary subsocial ancestors. It has been shown that the subsocial spiders of genus Stegodyphus tolerate a low level of inbreeding with low inbreeding depression, suggesting a possible stepping stone towards the fully inbred mating system found in social spiders.
Several social spiders including Achaearanea
Achaearanea
Achaearanea is a genus of spiders in the Theridiidae family.-Taxonomy:This genus used to include the extremely abundant common house spider, which was transferred to genus Parasteatoda in 2006, together with many other species. A. veruculata and many more species were moved to genus Cryptachaea in...
wau and Anelosimus
Anelosimus
Anelosimus is a genus of tangle web spider described by Eugène Simon, in 1891, from Venezuela. It includes the South American social spider Anelosimus eximius and related species....
eximius
Anelosimus eximius
Anelosimus eximius is species of social spider in the genus Anelosimus, native to the Lesser Antilles and the area from Panama to Argentina. Colonies can comprise several thousand individuals....
also swarm in an analogous way to the eusocial ants, bees and wasps
Hymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
. These species disperse and establish new colonies by means of synchronized emigrations of adult and sub-adult females. After courtship and copulation, but prior to oviposition, many females will emigrate to a new nesting site and deposit their eggs, forming a new colony. In this way social spiders are also extremely inbred, as there is limited migration of males or juveniles to different colonies, forcing the offspring to mate with one another decreasing genetic variation within the colonies. Occasionally males will emigrate with females or will emigrate from one colony to another but this is a rare event and has not been studied sufficiently to quantify for any social spider species. Females can also out-number males as much as 10:1 in many species; this too acts as a genetic bottleneck and further decreases the genetic variation of the species.
Most species of social spiders live in the tropical regions of the world where insect size and density is highest but several species reach into the eastern United States and other temperate areas. By building a communal web, it is thought that the spiders approximately maximize total biomass capture per spider. Having a larger web and multiple spiders to work together to subdue prey allows them to prey on larger organisms that would be impossible if they led a solitary existence. The colonies can grow large enough to take down birds and bats as well as very large insects.
Living in a colony also has another major benefit for spiders: cooperative nest maintenance. Nest maintenance does not rely solely on an individual in a colony setting and thus saves on a per-capita investment in maintaining silk structures. Predator defense is also increased in a colony with a large web and multiple individuals analogous to schools of fish or herds of mammals.
Quasi-social Spider Families and Genera
- Agelenidae
- Agelena consociataAgelena consociataAgelena consociata is a social species of funnel web spider that occurs in tropical forests in West Africa and lives in colonies of one to several hundred individuals.-Distribution:This species is found in rainforest habitats in Gabon...
- Agelena republicana
- Agelena consociata
- Desidae
- Phryganoporus candidusPhryganoporus candidusThe Foliage webbing spider is a spider widespread, but endemic in Australia. It is up to 10 mm long, silvery grey to brown with a pattern of light and dark brown markings on the abdomen. Unlike most other spiders, P. candidus lives socially at one stage: Spiderlings live together in a nest...
- Phryganoporus candidus
- Dictynidae
- Aebutina binotata
- Mallos gregalisMallos gregalisMallos gregalis is a spider species belonging to the Dictynidae family.It is known to be a social spider species, living in groups and signaling each others by vibrating their web....
- Eresidae
- Stegodyphus dumicola
- Stegodyphus mimosarum
- Stegodyphus sarasinorum
- Stegodyphus manaus (possibly social, see Kraus & Kraus 1992)
- Nesticidae
- Species not identified (Quintero & Amat 1995)
- Oxyopidae
- Tapinillus sp. (Aviés 1994; Avilés et al. 2001)
- Sparassidae
- Delena cancerides
- TheridiidaeTheridiidaeTheridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
- Achaearanea disparata
- Achaearanea vervortii
- Achaearanea wau
- Anelosimus domingo
- Anelosimus eximiusAnelosimus eximiusAnelosimus eximius is species of social spider in the genus Anelosimus, native to the Lesser Antilles and the area from Panama to Argentina. Colonies can comprise several thousand individuals....
- Anelosimus guacamayosAnelosimus guacamayosAnelosimus guacamayos is a species of social cobweb spider that occurs in the lower Ecuadorian sierra. The live in large nests , and are found in disturbed areas. Like rain forest cobweb spiders, they cooperate in the capture of prey and building of a communal nest....
- Anelosimus oritoyacu
- Anelosimus puravida
- Anelosimus lorenzo
- Anelosimus rupununi
- Theridion nigroannulatum
- Thomisidae
- Diaea ergandros
- Diaea megagyna
- Diaea socialis