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Wolf Spider

Arctosa cinerea

It is a rare and wonderful thing to glimpse the Arctosa cinerea wolf spider outside of its burrow. With females growing up to 17mm long, this wolf spider is among the largest in the Lycosidae family.

Description
Due to its washed-out spot pattern and its grey-brown and yellow-gray colouring, this spider is nearly impossible to spot against the ground when resting. Its eight legs – which are larger in males – exhibit a dark ringed pattern.

Distribution
The range of the Arctosa cinerea extends across all of Central Europe. In the Donau-Auen National Park it can be found on gravel banks along the shore.

Endangerment and Conservation Status
River regulation has eliminated most of the wolf spider's suitable habitats, a development which has likely not been good for the species. Thus the Arctosa cinerea is among the rarest of all spiders in the region today.

Behaviour
Ideal habitats are formed by untouched rivers with sandy and gravelly banks; in fact, this spider is sometimes called a "sand wolf spider" due to its preference of such sandy environments. Especially favourable are areas which are regularly flushed out by flooding and thus free of vegetation. The spider digs a finger-thick den in protected sandy ground and pads it with silk. By day, the spider remains in the burrow or lies in ambush for prey. By night, it leaves its hiding place. Using its sense of sight, it actively hunts down a variety of prey, including ground beetles, grasshoppers, insect larvae or other spiders, then pounces. Using its claw-like limbs (chelicerae) it injects venom and a secretion to aid digestion into its victim, then sucks it dry.
Once autumn has passed, spiders leave the shore area and find places to dig their hibernation burrows which are beyond the flood-prone areas.
Mating takes place in the spring, and starting around June the female carries a silk cocoon sac around with her containing eggs from which young spiders hatch starting in July. The young are also carried and watched over by the female.

Special Characteristics
The wolf spider's den is usually found in areas affected by high waters. If threatened by flooding, the den's entrance will be sealed. It is assumed that the Arctosa cinerea can survive by utilising a structure built of silk and the air bubble which is trapped within.
This spider is one of several endangered species which benefit immensely from river renaturalisation measures carried out in the Donau-Auen National Park.