Clive Muir and Sue Eatock go peering under rocks and stones to tell us all about the only protected spider in the EU – the Andalucian funnel web
IN Andalucía there lives a fairly large, black burrowing spider belonging to the venomous funnel web tarantula family. Its scientific name is Macrothele calpeiana and it belongs to the Hexathelidae group, which is normally associated with Australia, New Zealand, Asia, Central Africa and South America. There is one species known for the Mediterranean region (Walckenaer, 1805). The genus name is derived from Ancient Greek makro meaning big and thele, which refers to the spinnerets. The origin of the name calpeiana is from Calpe – a name the Phoenicians gave to Gibraltar.
This spider is known in Spanish as La Araña Negra de los Alcornocales, as within the Los Alcornocales Natural Park (Cadiz province) can be found the largest populations. Los Alcornocales is a forest of evergreen oak trees, mainly cork oak (Quercus suber) with its vast shady canopy creating an almost tropical feel. The temperatures and humidity levels in that area are more suited to these spiders’ requirements with a deep leaf litter for ease of burrowing.
Home sweet home
The first sign of their location is a silken white, sheet-like web anchored firmly to twigs, rocks, plants etc. This narrows to a tube near the centre, the entrance to the tunnel, which often leads to cooler depths underground. Although, there may be a labyrinth of several entrances to the one tunnel, the spiders are rarely communal.
The range of sites for these webs can be a simple scrape under a rock, vegetated banks, under logs, crevices in dry-stone walls, tree trunk bases and even tree hollows up to two metres above ground level. The underground portion can be to a depth of 80 centimetres, the upper part of which has a non-sticky web lining and the rest is left bare.
The day-time temperature at the burrow end can be 3 to 5 degrees Celsius cooler than at the entrance.
The Andalucian funnel-web spider is considered to be the largest in Europe and is easily recognisable. They are jet black with a glossy carapace and fine hairs on their legs and abdomen. The 1.5cm-long spinnerets, at the rear, almost look like extra legs. The body can be up to 3.5cm long and the stretched legs can reach a span of 8cm.
When under threat it can raise up its front legs into an attack position, exposing its fangs.
This is the only spider in Europe to be protected by the European Union Habitats Directive. They are found mostly in Cádiz and Málaga provinces with smaller numbers in scattered enclaves discovered in Huelva, Sevilla, Granada, Jaén, Gibraltar and the furthest north Badajoz, in Extremadura.
Two smaller communities found in North Africa are thought to be accidental imports from Spain. Further reports of their existence on the French side of the Pyrenees have been put down to their being carried with Olive trees and such. However, they are unlikely to survive cold winter temperatures.
These spiders are most active at night when they will wait at the tunnel entrance for prey to become glued onto the silken web. Their diet consists of small insects such as beetles, woodlice, millipedes and crickets.
When they feel the vibration of a trapped insect they will carefully approach, then bite the ill-fated prey with venom, which liquefies the victim as it is wrapped in silk. The venom is injected into the prey through openings in the tips of the pair of fangs. The glands that produce this venom are located in the two segments of the chelicerae (the parts to which the fangs are attached). “Dinner” is then taken into the private and protected retreat area behind the web to be devoured.
After eating they are fastidious cleaners. Any food debris will be discarded away from the web and around an hour of thorough grooming will follow.
Around April-May time, males wander around at night in search of a female with which to breed. It is thought there are pheromones in the silk of a female’s web that attract a mate. A gentle courtship ensues, as the male does not want to become the next meal.
The female then eats more over the ensuing weeks.
In early July, she seals herself into the retreat in order to produce the egg sac.
The females care for the egg sac by carrying it with them, manoeuvring to different parts of the tunnel to maintain the right levels of temperature and humidity.
The young have their first moult within the sac and she then helps to release them using her fangs. Possibly 100 to 250 eggs will hatch into baby spiders, known as spiderlings. They will accompany the female to the outer web after dark and are thought to feed on smaller prey.
At some point cannibalism among the young may occur, triggering dispersal of the survivors. At this point, many of the young will fall prey to other animals.
As they prefer little disturbed areas and are active at night, you will not normally encounter these spiders. Be cautious if you are moving logs, rocks etc and see a sheet like web. If provoked these spiders will rear up in a threatening manner and can even give an audible hiss. A famous close relative is the Australian funnel-web (Atrax robustus), whose bite can be fatal. Macrothele calpeiana venom is mild in comparison giving localized but painful swelling.
Clive and Sue launched wildsideholidays.com as an advertising medium for ethically-minded nature holiday businesses in Spain. The aim is to provide an internet site on which people searching for this type of holiday can easily find what they are looking for.
Together with iberianature.com, wildside holidays also run the iberianature forum (www.iberianatureforum.com) – the best online resource for learning about the nature of Iberia.