Ladybird spider (Eresus sandaliatus)

KingdomAnimalia
PhylumArthropoda
ClassArachnida
OrderAraneae
FamilyEresidae
GenusEresus
SizeMale length (excluding legs): 6-9 mm
Female length (excluding legs): 10-16 mm

The ladybird spider is classified as Endangered in the British Red Data Book and protected under Schedule 5 of the Wildlife and Countryside Act, 1981.

The attractive ladybird spider (Eresus sandaliatus) is one of the rarest in the UK. The males have a bright orange or vermilion back with four large black spots and two smaller ones, and superficially resemble a ladybird. Females and juvenile males are black and velvety. Both sexes and immature individuals have obvious large bulbous heads.

Found scattered across northern and central Europe; the ladybird spider is replaced by closely related species in the Mediterranean and elsewhere in Europe (including E. cinnaberinus). It is rare everywhere, especially in the UK. It used to be found on the Dorset heaths, and possibly in the Isle of Wight and Cornwall, but is now restricted to a patch of heathland in Dorset measuring about 50 metres across surrounded by a pine plantation.

The ladybird spider favours south-facing, sheltered slopes with well-drained sandy soil. It constructs a silk-lined burrow among sparse heather and lichen.

Ladybird spiders live in burrows with silk trip-wires covered with dense fluffy threads that radiate outwards to catch their prey. These include large insects, including devil's coach horse and violet ground beetles. The female rarely leaves her burrow and the male only emerges for two weeks in May to breed. Having found a burrow containing a female, the male plucks at the trip wires in a way that distinguishes him from prey; this protects him from becoming a meal. After mating, the female lays up to 80 eggs in a cocoon in her burrow during the summer and guards them until the spiderlings hatch in July or August. She feeds them on regurgitated food and finally the spiders eat their own mother, the female can therefore only breed once. The spiderlings disperse to make their own burrows in the following April, and are mature after three or four years.

Loss and neglect of habitat is the chief reason for the scarcity of the ladybird spider. Their existing patch of Dorset heath is threatened by invading rhododendron scrub and pine seedlings.

By 1993 it was estimated that there were probably no more than 50 individuals left in Britain and the ladybird spider was added to English Nature's Species Recovery Programme. The first priority was to manage the spiders' existing site and enlarge the area of suitable habitat. The next task was to establish a captive breeding colony. It was considered too risky to take spiders from the Dorset colony so, in partnership with the Federation of Zoological Gardens and the Wildfowl and Wetlands Trust, English Nature obtained permission to collect spiders from Denmark. Captive mating was successfully achieved in 1995. A large number of spiderlings hatched and these were taken into the care of the Wildfowl and Wetlands Trust at Martin Mere Nature Reserve Centre in Lancashire since when some have been reared to maturity.

The Dorset spider site was enlarged by clearing Rhododendron and pine with the help of the Forestry Commission and the ladybird spiders began extending their territory with the help of some hot, dry summers. By 1996, the number of burrows counted had reached 139. Other suitable heathland sites have been surveyed and, with the lessons learned from the Danish spider colony, hopes were high that an establishment using captive bred British spiders could get underway. However, the UK wild population of ladybird spiders seems to be increasing very happily. By the end of the summer of 2000 nearly 600 individuals had been counted and eight occupied burrows were moved successfully. This has led to a change of plan and the Dorset site may now prove sufficiently established to allow re-introductions to be made to former known sites using pure-bred UK spiders instead of captive bred ones.

The UK BAP Species Action Plan is available on-line at:
http://www.ukbap.org.uk
Visit the British Arachnological Society website:
http://www.britishspiders.org.uk/index.html

Information supplied by English Nature
http://www.english-nature.org.uk and authenticated by Dr Peter Merrett of the British Arachnological Society:
http://www.britishspiders.org.uk/index.html