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Images and Species Descriptions
Text and photographs © 2011 Jørgen Lissner
The Spiders of Europe and Greenland
Family: Philodromidae (Running Crab Spiders)
Biology: The Philodromidae is a medium sized spider family comprising a world fauna of about 522 species in 29 genera. They range in size from small to large (2-16 mm body size). Philodromids have agile flattened bodies and laterigrade legs, which in most genera are of about the same lengths and thickness. They move rapidly around as their claw tufts and scopulae provide good adhesion to slippery surfaces. Species of Philodromus are able to move from one side of a leaf to the other or halfway round a stem so quickly that human eyes hardly manage to follow the motion. Once they stop running they instantly adopt a motionless, camouflaged posture with the legs stretched to closely follow the contour of the substrate. The laterigrade legs allow them to slip in to bark crevices etc. without raising the leg joints almost as they are 2-dimensional creatures. Many species are cryptic coloured and blend in with the substrate being very difficult to spot. Most species inhabit the foliage, branches, and stems of bushes and trees but many are also found running about at ground level, e.g. species of Thanatus. Species of Tibellus are elongated and adapted to a life on grass stems. Many species of Philodromus are capable of changing the depth of colour to conform to different backgrounds. Philodromus margaritatus occurs in two colour forms one of which is mottled in grey and brown perfectly camouflaged on bark. The second colour form Philodromus margaritatus forma laevipes is lighter with dark blotches and perfectly camouflaged on lichen covered stems. Most species in the northern temperate regions hibernate as subadults becoming adult in spring. The female constructs a woolly egg sack across a leaf, under bark etc. and some species stands guard directly over it while other species sit nearby.
Characters of family: The philodromids belong to the group of araneomorph, ecribellate spider families having 8 eyes and 2 tarsal claws. The eyes are not situated on tubercles. In many species they are fairly equal in size, however in some species all eyes of the anterior row or just the anterior medials are larger. The eyes are arranged in two recurved rows of four with the posterior row sometimes more strongly recurved than the anterior row. All legs are of about the same lengths or legs II alone longer (twice as long in Ebo). The legs are laterigrade so that the morphologically dorsal surface is rotated about one quarter of a turn to a posterior position. Tarsi I and II are provided with scopulae and claw tufts composed of spatulate hairs (thickest point on the distal half). The anterior tibia are sometimes provided with a row of long spines. Other diagnostics characters which separate philodromids from the related thomisids and sparassids include the lack of a colulus and the absence of tapetum in the secondary eyes. The carapace is as long as wide or elongate, rather flattened usually with fovea absent. It is densely clothed in recumbent plumiform or spatulate hairs. The carapace is frequently marked by a lighter longitudinal band of about the same width as the eye rows. The sternum is oval corresponding with carapace form, apex blunt between coxa IV. The cheliceral fang furrow usually has no teeth. The labium is longer than wide. Endites are longer than labium and converge in front. The female palp has a small toothed claw. The shape of the abdomen is oval, in some species slightly longer than wide, in others quite elongate. In most species the widest point of the abdomen is found in the rear half. It is densely covered with recumbent hairs and sparsely covered with longer, erect hairs. The cardiac mark is darker than the surrounding abdomen, sometimes very distinctive as in e.g. Thanatus. It may be followed by a series of chevrons. The spinners are simple. The tracheal spiracle is situated close to the spinners. The epigyne is usually small having a median septum. The male palp is furnished with a tibial apophysis; the shape of which is important when identifying to species level using the stereomicroscope.
Genus: Philodromus Walckenaer, 1826
Characters of genus: The spiders of this genus have flattened bodies, and latigrade legs that often are held very close to the substrate such as all segments appear as being in the same plane. Most species have relatively short abdomens, only slightly longer than broad and with the widest point behind midway. In this respect they resemble many species of the Thomisidae. The posterior row of eyes is recurved and the distance between the medial eyes is about 1.5 times the distance between a median and a lateral eye. Most species live on plants on which they are able to move around rapidly, their flat bodies enable them to hide under bark. Some species are extremely well camouflaged and almost impossible to spot unless they move. Other species are qiute conspiceous even when motionless.
Philodromus glaucinus Simon, 1870
Range: Bulgaria, France (Corsica), France (Mainland), Greece (Dodecanese Islands), Greece (Mainland), Italy (Mainland), Italy (Sardinia), Macedonia, Malta, Portugal (Mainland), Russia (Southern European), Spain (Balearic Islands), Spain (Mainland) (van Helsdingen 2009.1). Global range: Mediterranean to Azerbaijan (Platnick 10.0).
Genus: Thanatus C. L. Koch, 1837
Characters of genus: The members of this genus have oval, sligthly elongate abdomens with a clear cardiac mark. The abdomen is the least flattened among the crab and running crab spiders and the legs are the least laterigrade. Therefore they bear some resemblance to the wolf spiders (Lycosidae), but they eyes are quite different. Species of Thanatus differ from species of Philodromus by having legs IV the longest and the strongly recurved posterior row of eyes. The anterior row is short. Eyes of the posterior row are almost uniformly spaced. The carapace and abdomen is without a dark longitudinal band.
Thanatus arenarius L. Koch, 1872
Range: Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Finland, France (Mainland), Germany, Greece (Crete), Greece (Dodecanese Islands), Greece (Mainland), Greece (North Aegean Islands), Hungary, Italy (Mainland), Latvia, Lithuania, Macedonia, Moldova, Norway (Mainland), Poland, Romania, Russia (Central European), Russia (Eastern European), Russia (Southern European), Slovakia, Spain (Balearic Islands), Spain (Mainland), Sweden, Ukraine, Yugoslavia (van Helsdingen 2009.1). Global range: Europe to Central Asia (Platnick 10.0).
Female abdominal markings.