Palystes superciliosus – the Rainspider

We watched in  fascination the construction of the rain spider’s egg sac  outside  our bedroom door.  Most of the hard work seem to have been done during the night; leaves were gathered and somehow attached to form a ‘globe’, carefully anchored to the wall, glass and creeper, then covered with a delicate layer of silk. At first a small slit was left open, possibly for the spider to enter the sac, after she laid the eggs, the opening was carefully sealed.

Night time construction of Egg sac

Sac completed, note the effective anchoring

The common rain spider (Palystes superciliosus),  is a species of huntsman spider native to Southern Africa. It is the most common and widespread species in the genus Palystes. It has a body length of 15–36 mm and a leg span of up to 110mm. The species was first described by Ludwig Carl Christian Koch in 1875.  Palystes is derived from either the Latin “palaestes” or Greek “palaistes” meaning wrestler. These are the large spiders, often referred to as “tarantulas”, that cause havoc by entering buildings during summer or before rain.

The size of these spiders, combined with the yellow and black banding on the underside of the legs exposed when the spider is in threat pose, give them a fearsome appearance. An experiment was done in 1959 where a Palystes superciliosus was allowed to bite an adult guinea pig on the nose. The guinea pig died within 7 minutes, leading to a belief that the spider’s venom was dangerous.  However, further research on anaesthetized guinea pigs showed that the original guinea pig had actually died of shock, rather than as a result of the spider’s venom. In humans the bite is no more dangerous than a bee sting. It causes a burning sensation, and swelling which lasts for a few days. Recovery is spontaneous and complete.

Its preferred habitat is scrubland and savannah woodland. Spiders in the genus Palystes are commonly called rain spiders, or lizard-eating spiders. Palystes spiders will often enter homes before rain, where they will prey on geckos (usually Afrogecko porphyreus in Gauteng, the Western Cape, or Lygodactylus capensis in the eastern parts of southern Africa). Males are regularly seen from August to December, probably looking for females.

After mating in the early summer, the female constructs a round egg sac about 60–100 mm in size made of silk, with twigs and leaves woven into it. These egg sacs are commonly seen from about November to April. The female constructs the sac over 3–5 hours, then aggressively guards it until the spiderlings, who hatch inside the protective sac, chew their way out about three weeks later. Females will construct about three of these egg sacs over their two-year lives. Many gardeners are bitten by protective Palystes mothers during this period.

After hatching from the eggs the spiderlings stay within the egg sac until they undergo their first moult – their small cast skins can be seen inside the old egg sac. After this they emerge, having cut a neat hole in the sac with the fangs (perhaps aided by a silk digesting fluid and sometimes helped by the female from outside). The spiderlings cluster together initially, still living largely upon the remnants of yolk sac in their abdomens.

After several days or weeks, the spiderlings begin to disperse gradually away. This is necessary to avoid competition for food and prevent cannibalism among the hungry siblings.

Having survived the perils of wasp, fly and mantispid lacewing egg parasitism in the egg sac, the life of spiderlings remains beset with dangers. Only a few will avoid being eaten and find adequate shelter and food to ensure their survival to adulthood. Very few will reach adulthood, it is therefore necessary to protect these creatures  and not to kill them.

People tend to fear rainspiders mainly because of their big size (these guys do get to be very large indeed!) and the fact that they so often wander into our homes. They also put up quite a show when provoked, raising their front legs and exposing their fangs, often running towards and attempting to bite anything brought close to them. Unfortunately, this usually ends in the poor spider simply being killed – either suffering a prolonged death by being sprayed with insecticide not made for anything nearly as large as a rain spider, or by simply being squashed. It is so sad that people in this day and age still do not realise that the rain spider means them no harm and if left alone will most likely find its own way out again, to where it will not be disturbed by lights and people. The most ironic thing is probably killing one of nature’s best pest controllers with the very insecticide that was meant for the rain spider’s natural prey.

If you do happen to find a rain spider in your home, what do you do? Well, easy. Usually just leaving it alone works pretty well and the spider will make its own way out again. If having the spider inside your home bugs you, taking it out is very simple. A large container and a poking instrument of sorts is all you need. Simply place the container in front of the spider and then gently poke its backside with your poking instrument. Now I have to add, these spiders are pretty aggressive, so if you are afraid of spiders rather get someone else to do it! Also, if possible take them out during the day – as they are nocturnal hunters they are almost inactive during the day and it makes taking them out a breeze. At night they tend to run around a bit. Once the spider is in your container (with a lid on preferably), take it out and release it in a remote spot in the garden which has  plenty of plant growth for the spider to hide in.

Palystes is also regularly seen in more unfortunate circumstances where it is being dragged around by a wasp or often the wasp is missing and all one finds is what seems to be a dead spider on the pathway. What has in fact happened is that the spider has been stung and immobilized by a female wasp of the family Pompilidae. These wasps hunt only spiders that they sting and paralyse and then stock each of their nests with a paralyzed spider, lay an egg on it and then seal the nest. The wasp eggs then hatch and the larvae have live fresh food on which to feed. All peripheral tissue is eaten first and lastly the vital parts so the meal stays fresh long enough for the larva to mature and then pupate.

 

Info: Wikipedia, Moreleta Kloof Nature Reserve, Larsen, N. 2005. More than just a bag of old leaves: A look into our Rain Spiders. Newsletter of the Spider Club of South Africa 20 (2): 12