| Anelosimus eximius | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Theridiidae |
| Genus: | Anelosimus |
| Species: | A. eximius |
| Binomial name | |
| Anelosimus eximius Keyserling, 1884 | |
Anelosimus eximius is a 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. [1]
The natural range of A. eximius extends from Panama to southern Brazil in its north-south direction and from Trinidad and eastern Brazil to Peru in its east-west direction. It inhabits rainforest and second-growth forest habitats. [1]
A. eximius webs consist of a roughly oval, horizontal sheet of nonadhesive silk, retreats constructed from leaves curled and held in place with silk, and vertical threads, referred to as "knockdown threads", that extend from the sheet and retreats to branches above the web. Webs can be found from ground level to up to 20 meters of height within forest canopies. In size, webs can range from 10-25 cm in length to over 3 m across. The smallest webs are typically home to only a few spiders, while the largest can contain hundreds or thousands of individuals. [1]
Anelosimus eximius are classified as a social spider species because they engage in shared brood care and cooperate to capture prey within their web, which allows them to capture prey much larger than a single individual would be able to. [2] [3]
Mature colonies consist of a mixture of adult and immature individuals of both sexes. The gender ratio is skewed towards females, as males only make up between 5% and 22% of a given colony's population. Reproduction occurs throughout the year. Young are fed by regurgitation; females will feed young other than their own. [1]
The sociality of Anelosimus eximius aids in the increased fitness of the species. One potential cost of sociality in Anelosimus eximius is that they produce fewer egg sacs. However, each egg sac holds more individual offspring than most arachnid egg sacs would normally hold. Thus, the benefits seem to outweigh the costs. [4]
It is difficult to explain how sociality has evolved from a typically solitary animal. One trait that has facilitated this shift is the lack of discrimination against foreign offspring. It has also been questioned whether the alloparental behavior of Anelosimus eximius was an ancestral trait or if the species had to overcome discrimination[ when defined as? ] in order to gain their trait of sociality. Through studies on social and sub-social species that observed reactions to foreign offspring, scientists discovered that the species did not need to overcome discrimination; both sub-social and social species of arachnids showed no discrimination towards foreign offspring. [3]
Anelosimus eximius are notable for favoring large prey items, which make up a much larger portion of their diet compared to solitary or less social species. A. eximius colonies are recorded to primarily capture prey in the 10-20 mm range with peaks reaching up to 50 mm or more, while solitary species from the same locations rarely take prey exceeding 10 mm in size. In a comparative study, large prey items such as wasps, bees, coleopterans, lepidopterans, heteropterans, blattodeans and orthopterans were found to make up 74.8% of the diet of A. eximius but only 22.5% of the diet of Anelosimus jucundus , a related but less social species. Smaller prey is often ignored by the spiders and is typically able to escape from the web. A. eximius webs typically makes use of non-sticky "knockdown strands" up to several meters long which are strung across open flyways through which larger flying insects tend to move. Insects that collide with these strands fall into the web below, where their struggling movements attract the spiders. Large groups of spiders will swarm captured insects; larger prey and animals that struggle longer will typically attract more spiders. Groups of 30-50 spiders or more can be observed attacking a single large insect. [5] Large prey items are afterwards fed on collectively by multiple individual spiders. [1]
A. eximius webs do not capture large numbers of prey, but the prey that are caught are significantly larger than most prey captured in the webs of other individual social or antisocial spider species. Thus, their techniques provide more nutrients than other social spider colonies may obtain. These techniques are most efficient in Anelosimus eximius colonies of about 1,000 individuals. [6] [7]
Colony distribution is known to occur in two manners: budding and dispersal. Budding occurs when an established colony splits into two or more independent webs, either due to being broken by falling debris or other accidents or due to a number of spiders establishing a secondary web in its vicinity. Dispersal occurs when a large number of mated females leave the colony and disperse individually, each creating a solitary web. These solitary females may be joined by other dispersing individuals, typically other females whose attempts to establish a new colony have failed. Newly-founded webs have high failure rates, but are more likely to survive if joined by other females. New colonies with multiple founders tend to be encountered near established webs, while single-founder webs are usually more distant. Males and juveniles do not leave their natal webs during dispersal events. [1]
These patterns of distribution lead to A. eximius colonies often occurring in aggregations of two to forty distinct webs, which may be separated from other such clusters by distances ranging from a few meters to several kilometers. Colonies within a single cluster tend to be derived from budding events, while distinct clusters may originally become established through dispersal founder events. Neighboring colonies are typically in close proximity, and may share the same knockdown threads or be in physical contract. Gene flow among colonies within a single cluster is high. Gene flow is low to absent among distinct clusters, as individual spiders do not typically move between unrelated colonies. It is however possible that new colonies might be established by a number of unrelated females. Consequently, populations of A. eximius exist as mosaics consisting of groups of geographically and genetically distinct colony clusters. [1]
A. eximius is preyed upon by Zatypota parasitoid wasps, the larva of which feed on the spider's hemolymph and induce the spider to move away and spin an abnormal web, serving as a cocoon for the pupating insect to feed on the spider and emerge. The process is particularly noteworthy because the actions induced do not seem to be part of the spider's typical behaviour repertoire. [8]
Spider behavior refers to the range of behaviors and activities performed by spiders. 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 which is reflected in their large diversity of behavior.
Stegodyphus lineatus is the only European species of the spider genus Stegodyphus. Male S. lineatus can grow up to 12 mm long while females can grow up to 15 mm. The colour can range from whitish to almost black. In most individuals the opisthosoma is whitish with two broad black longitudinal stripes. Males and females look similar, but the male is generally richer in contrast and has a bulbous forehead. The species name refers to the black lines on the back of these spiders. S. lineatus is found in the southern Mediterranean region of Europe and as far east as Tajikistan.
Anelosimus is a cosmopolitan genus of cobweb spiders (Theridiidae), currently containing 74 species. Anelosimus is a key group in the study of sociality and its evolution in spiders. It contains species spanning the spectrum from solitary to highly social (quasisocial), with eight quasisocial species, far more than any other spider genus. Among these is the South American social species Anelosimus eximius, among the best studied social spider species.
A social spider is a spider species whose individuals form relatively long-lasting aggregations. Whereas most spiders are solitary and even aggressive toward other members of their own species, some hundreds of species in several families show a tendency to live in groups, often referred to as colonies.
Anelosimus studiosus is a subsocial tangle web spider or theridiid spider living in both North America and South America. In 2012, genetic analysis revealed a previously identified species, A. tungurahua, is in fact the same species as A. studiosus.
Vespula pensylvanica, the western yellowjacket, is a Nearctic species of wasp in the genus Vespula. It is native to regions of North America, largely in areas with northern temperate climates. Its reproductive behavior is constrained by cold weather, which successfully reduces the number of western yellowjackets in cold months. However, in the absence of cold weather, this wasp's population can explode. The western yellowjacket has become particularly invasive in the Hawaiian Islands, resulting in their label as a major pest.
Cyrtophora citricola, also known as the tropical tent-web spider, is an orb-weaver spider in the family Araneidae. It is found in Asia, Africa, Australia, Costa Rica, Hispaniola, Colombia, and Southern Europe and in 2000, it was discovered in Florida. C. citricola differs from many of its close relatives due its ability to live in a wide variety of environments. In North America and South America, the spider has caused extensive damage to agricultural operations.
Spiders are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms. Spiders are found worldwide on every continent except Antarctica, and have become established in nearly every land habitat. As of November 2023, 51,673 spider species in 136 families have been recorded by taxonomists. However, there has been debate among scientists about how families should be classified, with over 20 different classifications proposed since 1900.
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. This species is found in rainforest habitats in Gabon. It favors dense forests along creeks where colonies can build huge complex webs.
Polistes metricus is a wasp native to North America. In the United States, it ranges throughout the southern Midwest, the South, and as far northeast as New York, but has recently been spotted in southwest Ontario. A single female specimen has also been reported from Dryden, Maine. Polistes metricus is dark colored, with yellow tarsi and black tibia. Nests of Polistes metricus can be found attached to the sides of buildings, trees, and shrubbery.
Anelosimus oritoyacu is a species of tangle-web spider found in Ecuador and Mexico at altitudes from 1,800 to 2,000 metres. It is subsocial, although it has some features which distinguish it from other social or subsocial spiders in the genus. It has long-lived nest sites, unlike the social spider Anelosimus eximius which has more transitory nest sites, and its webs do not have aerial threads found in other social and sub-social species. It has a female-biased sex ratio, which is indicative of social behavior, although its sex ratio is smaller than other social species. It was first identified as distinct from Anelosimus studiosus in 2006 by Ingi Agnarsson. It is named for Oritoyacu, Ecuador, where the type specimen was collected.
Anelosimus pratchetti is a species of tangle-web spider found in New South Wales, Australia. Initial field observations indicate it is a subsocial spider. It lives in low elevation environments, including beachfront mangrove forests. It was identified by Ingi Agnarsson in 2012, who named the species after Terry Pratchett, whom Agnarsson described as "a comic genius".
Anelosimus jabaquara is a species of spider found in subtropical, humid, lowland forests in Brazil. Anelosimus jabaquara was first described by Herbert W. Levi in 1956. These spiders cooperate to spin and repair the colonial web, capture prey, and care for the brood. Colony size is small, and the sex ratio is biased towards females.
Leticia Avilés is an Ecuadoran evolutionary biologist and ecologist who studies the evolution of social behavior and the evolution of life history traits in metapopulations. Her methods include a combination of theory and empirical work, the latter using social spiders as a model system. Her research on these organisms has addressed questions such as why some spiders live in groups, why do they exhibit highly female-biased sex ratios, and why have they evolved a system where individuals remain in the natal nest to mate from generation to generation.
Stegodyphus sarasinorum, also known as the Indian cooperative spider, is a species of velvet spider of the family Eresidae. It is native to India, Sri Lanka, Nepal, and Myanmar. This spider is a social spider that exhibits communal predation and feeding, where individuals live in large cooperatively built colonies with a nest or retreat constructed of silk woven using leaves, twigs, and food carcasses, and a sheet web for prey capture.
Matriphagy is the consumption of the mother by her offspring. The behavior generally takes place within the first few weeks of life and has been documented in some species of insects, nematode worms, pseudoscorpions, and other arachnids as well as in caecilian amphibians.
Philoponella oweni is a species of spider belonging to the family Uloboridae, the cribellate orb weavers. They are around 4.7–7.1 mm long in length and are primarily found in the arid southwestern parts of the United States. These spiders are most known for being semi-social, a rare trait within spiders. Semi-social, in the case of P. oweni, refers to the coexistence of facultatively communal and solitary females within the same habitat. These groups usually form in response to environmental factors, and often never involve true cooperation. This lack of true cooperation means these spiders do not share prey items, do not work together when spinning webs and do not care for one another's young. The coexistence of both solitary and communal species within the same habitat can be explained by both tactics have similar net reproductive success values. This was can be explained by comparing the number of eggs within egg cases to the number of surviving offspring for both tactics. The number of surviving offspring of communal and solitary beings does not vary significantly, which mostly due to the parasitism by pteromalid wasps. These wasp which prefer consume and parasitize communal P. oweni webs and eggs, counteracting the increase of eggs per egg case that communal spiders tend to produce over solitary.
Stegodyphus dumicola, commonly known as the African social spider, is a species of spider of the family Eresidae, or the velvet spider family. It is native to Central and southern Africa. This spider is one of three Stegodyphus spiders that lives a social lifestyle. This spider has been studied living in large natal colonies in large, unkempt webs. Each colony is composed mainly of females, where a minority act as reproducers, and a majority remain childless and take care of the young. Males live a shorter lifespan, during which they will largely remain in the natal nest. Females are known for extreme allomaternal care, since all females – even unmated virgin ones – will take care of the young until they are eventually consumed by the brood.
Metepeira incrassata, also known as the colonial orb-weaving spider, belongs to the spider family Araneidae and genus Metepeira. They are most famous for their social organization and group living behavior. They are generally found in tropical rainforest and agricultural sites in Mexico, and their habitats tend to be highly productive. Their group sizes are relatively larger than other colonial spiders, typically ranging from hundreds to thousands of individuals. 99% of the females are observed to participate in colonial living, generally with at least two other individuals. Because most M. incrassata females are communal, the colonies are often dominated by larger males. There is minimal sexual dimorphism observed in M. incrassata. Unlike other orb-weaver spiders, M. incrassata builds a colonial web by connecting each spider's individual webs together through semi-permanent framelines. These colonial webs of M. incrassata are prone to invasion by kleptoparasitic and araneophagic spiders such as the Theridiidae family. The reproductive cycle of M. incrassata occurs throughout the entire year, with multiple generations sharing the same time period. Within their colonies, M. incrassata is seen to change locations. Larger, fertile females with egg sacs prefer to reside in the central area of the group for increased protection from predators, while the younger spiders are mostly found in peripheral positions. Larger adult M. incrassata are also known to finish web-building earlier than smaller ones, gaining an advantage in strategically positioning themselves.
Parawixia bistriata is a spider species found mainly in South America. It is known to have social foraging behavior. Due to its complex social system, it can live in habitats with various resource levels. Recently, its social behavior has been well-studied. Also, this species can collectively change its web structure in response to changes in prey type. They live collectively in web systems and thrive in both dry and wet climates. The size of its body is very small, typically 2 cm (0.8 in) long.
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