Spider Colonies

This page summarizes the tendency of spiders to form colonies and to live in integrated societies rather than in a solitary fashion.

The female rarely, if ever, seeks out the male but will sometimes tolerate his continued presence nearby provided he avoids making provocative movements. She is normally well aware of his presence, perhaps because of vibrations transmitted through her web (assuming she has one), although the males of species such as Arachnura higginsi are much smaller than the females and appear to go almost unnoticed. For some species there may even be several males lurking nearby, all hoping to be able to make a successful approach. Males of Deliochus zelivira even manage to survive indefinitely in close proximity to a female, perhaps because she is usually in her retreat and the male is shielded by leaf fragments and webbing.

For a typical spider species the actual mating is preceded by an elaborate courtship ritual in which the male shows great enthusiasm and the female appears aggressive or indifferent. It is probably most common for a male to approach a female from behind and/or from underneath in order to stay out of her field of vision. The eventual coupling is usually abdomen to abdomen, though the two sexes may be facing in opposite directions, but sometimes the male positions himself on one side of the female. For mygalomorphs such as the funnel-web species, Hadronyche infensa, the approach is front-on and the male makes use of structures such as leg spurs to restrain the female from attacking during sperm transfer. Once mating has occurred the male of some species may escape to repeat the process, not necessarily with the same female, or may do little to avoid being eaten by his mate. This is particularly true for those species for which the males die soon after maturing even if they have never managed to find a female to mate with.

Maternal behaviour
Many kinds of spiders lay batches of eggs then move away, leaving the emerging spiderlings to fend for themselves. However, other spider species do exhibit some degree of maternal care for their egg sacs and for the spiderlings, at least until the young spiders have moulted a couple of times and are now half grown. Huntsman spiders such as Holconia immanis exhibit this phenomenon well and it is not uncommon for a collector to strip a piece of loose bark from a dead gum tree only to suffer a shower of about 30 quite large huntsman spiderlings along with the adult female.

Fortunately, these spiders then try to escape rather than attack the person who destroyed their temporary home. A different form of maternal care is practised by wolf spiders such as Lycosa godeffroyi. Lycosid females typically drag their egg sacs around behind them when they wander above ground and then subsequently piggyback the newly hatched spiderlings on their upper surfaces. Presumably, this latter practice also allows efficient dispersal of the young spiders.

Interactions of spiderlings
For species where the spiderlings have been left to fend for themselves it is common to find them gathered together, often on a small primitive web. However, this communal effort appears to be a temporary phenomenon and cannibalism among the spiderlings means that only the strongest spiderlings survive to disperse and grow to adulthood.



Utilisation of available resources
Most instances of apparent colony formation among spiders are not genuine examples of social behaviour but are simply individual spiders living in close proximity to each other in order to make use of optimal circumstances. Thus, in the same way the humans gather together in cities to benefit from the conveniences that cities offer but still live in discrete houses, many spider species will build webs in the same shrub or dead tree because it is such a good location for insect-catching. In South-east Queensland it is not uncommon to find large dead trees with dozens of individual Nephila edulis webs attached and it is often difficult to determine where one web finishes and the next one starts. However, the spiders seem to know which is their own web and rarely stray onto that of their neighbours. Cyrtophora moluccensis webs are divided into inner areas of uniform tent web and outer areas of tangled silk and occasionally are so extensive that they appear to be a single massive web. The same situation is said to exist for Badumna socialis webs in the Jenolan Caves of New South Wales.



Mutualism
This term is defined as a situation in which two different species or several members of the same species live in a 'colony' arrangement which is beneficial to all individuals involved. Totally social communities are to be found among honey bees and ants, some members of the community acting as workers, others as soldiers, and one or a few as egg-layers. Spiders probably never exhibit this kind of organised social behaviour but a few temporary or 'opportunistic' instances of mutualism among spiders are known. In Australia the spider most often mentioned as exhibiting colonial behaviour is the desid, Phryganoporus candidus. This species forms dense masses of webbing in which there are many individuals (including other predators and scavengers) using a communal network of tunnels.

However, the non-territorial interaction that occurs in this comunal nest only involves immature specimens and each spider (apart from the original adult female) leaves the colony before maturing. Some authors have suggested that small theridiids such as Argyrodes species display a better example of mutualism. These theridiids don't need to make their own webs because they spend most of their time on the edges of araneid webs and may serve to keep the orb-weaver's web tidy while feeding on trapped insects that are too small to attract the attention of the araneid itself. Realistically, this may not be true social behaviour either in that the araneid is probably not even aware of the smaller spider's existence and is actually being deprived of a portion of its food source.



Some related sources of information
The page on growth and reproduction in spiders contains some information relevant to what is covered in the above paragraphs.