Agelena consociata

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Agelena consociata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Agelenidae
Genus: Agelena
Species: A. consociata
Binomial name
Agelena consociata
Denis, 1965

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[edit]

This species is found in rainforest habitats in Gabon. It favours dense forests along creeks where colonies can build huge complex webs.

Description[edit]

Male and female spiders are similar in size but there are fewer males than females. This spider is a dull brown colour with two broad lateral grey stripes. The legs are banded in brown and black. Both body and legs are covered with short hairs.[1]

Ecology[edit]

The web structure consists of individual nests connected by flat sheets of silk supported by vertical scaffolding threads. There are a number of retreat holes leading into the nests and groups of nests are often joined by more sheets of webbing and scaffolding.[2]

Although these spiders live in colonies consisting of many individuals, each spider acts and breeds individually and there is not any specialization of role as there is with social insects. The spiders cooperate in the maintenance of the web and the catching of large prey. As many as forty spiders have been seen feeding on one victim and adults often regurgitate to feed juveniles that are not their own offspring.[3][4] In fact there is considerable tolerance of the young which continues into adulthood in a way that is not seen in non-social spiders. When spiders are introduced into a colony from elsewhere, they are accepted; it is the species that matters, not the origin. This again is in contrast to social insects which defend their nests against outsiders. The spiders communicate through the use of pheromones and also through the vibrations of the web structure.[5]

A new colony can be started by a single female spider, a group of immatures or by a group of adults and juveniles. Eggs are laid at times of high humidity and there are a large number of cocoons between November and January.[6]

No evidence was found of active dispersal from a colonial site. New colonies are usually founded as a result of accidental destruction of an existing colony by storm or falling branches. Another means of dispersal over larger distances is likely to be passive transport of spiders by bats or other vertebrates. On examination of the genetic makeup of the colony, it was found that colonies separated by thirty metres were likely to be as genetically distinct as colonies separated by many kilometres.[7]

The web structure may appear empty during the day because the spiders lie hidden, emerging at nightfall to repair the web and hunt. Most of the prey is caught at night.[1]

It is thought that this species may have developed colonial behaviour because of the difficulty of dispersal in the rainforest environment. Other reasons might be the individual cost of repeatedly repairing a web frequently damaged by tropical downpours and particularly, because of the continuity of generations that occurs, a thing that is not possible in cooler climates.[2]

References[edit]

  1. ^ a b Le monde des insectes
  2. ^ a b The ecology of the cooperative spider Agelena consociata in Equatorial Africa
  3. ^ Riechert, S . E. 1985 . Why do some spiders cooperate?, Agelena consociata, a case study. Insect Behay. Ecol. symp . 1984 . Florida Entomologist, 17 :105-116. et al 1985
  4. ^ Riechert, S . E. and J. Luczak . 1982 . Spider foraging : Behavioral responses to prey . Pp. 353-385, In Spider Communication : Mechanisms and Ecological Significance (P . N. Witt and J . Rovner, eds.). Princeton Univ . Press, Princeton, New Jersey.
  5. ^ Krafft, B. 1982. Eco-ethology and evolution of social spiders . Pp. 73-84. In Social Insects in the Tropics (P. Jaisson, ed.) Universite Paris-Nord, Paris.
  6. ^ Darchen, R . 1975 . La fondation de nouvelle colonies d’Agelena consociata et d’Agelena republicana, araignees sociales due Gabon . Problemes eco-ethologiques . C. R. IIIeme Coll . Arachnol . Express. franc ., Les Eyzies. pp. 20-39.
  7. ^ Dispersal and population-genetic structure of the cooperative spider Agelena consociata in West African rainforest