The raft spider, scientific name ''Dolomedes fimbriatus'', is a large semi-aquatic

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

of the family

Pisauridae Nursery web spiders (Pisauridae) is a family of Araneomorphae, araneomorph spiders first described by Eugène Simon in 1890. They resemble wolf spiders (Lycosidae) except for several key differences. Wolf spiders have two very prominent eyes in ad ...

found throughout north-western and central Europe. It is one of only two species of the genus ''

Dolomedes ''Dolomedes'' is a genus of large spiders of the family Pisauridae. They are also known as fishing spiders, raft spiders, dock spiders or wharf spiders. Almost all ''Dolomedes'' species are semiaquatic, with the exception of the tree-dwelling ...

'' found in Europe, the other being the slightly larger ''Dolomedes'' ''plantarius'' which is endangered in the UK.

Habitat and description

Raft spiders are

semi-aquatic In biology, semiaquatic can refer to various types of animals that spend part of their time in water, or plants that naturally grow partially submerged in water. Examples are given below. Semiaquatic animals Semiaquatic animals include: * Verte ...

and adults inhabit freshwater wetlands, specifically wet heaths and acid swamps; although juveniles are predominantly found in terrestrial vegetation surrounding wetland areas. Adults are dark brown with a conspicuous white, cream or yellow stripe along both sides of their abdomen and thorax. Juveniles are similar in appearance but often have green translucent legs. As is common in other spiders, female raft spiders (body length: 9–22mm) are usually larger than males (body length (9-15mm). Dolomedes fimbriatus was described in chapter 5 of the book ''

Svenska Spindlar The book ' or ' (Swedish and Latin, respectively, for "Swedish spiders") is one of the major works of the Swedish arachnologist and entomologist Carl Alexander Clerck and was first published in Stockholm in the year 1757. It was the first compre ...

'' by the Swedish arachnologist and entomologist

Carl Alexander Clerck Carl Alexander Clerck (1709 – 22 July 1765) was a Sweden, Swedish entomologist and arachnology, arachnologist. Clerck came from a family in the petty Swedish nobility, nobility and entered the University of Uppsala in 1726. Little is known of hi ...

. It is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of its genus.

Behaviour

Like many other species of the genus ''

'' (Greek translation= crafty or wily), the raft spider typically hunts on the surface of the water with its front appendages outstretched and relies on aquatic vibrations to detect prey. Juveniles are thought mainly to hunt in terrestrial vegetation. Their diet consists largely of freshwater

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s such as water beetles, pond striders and dragonfly larvae, but they occasionally feed on small

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

s such as

stickleback The sticklebacks are a family of ray-finned fishes, the Gasterosteidae which have a Holarctic distribution in fresh, brackish and marine waters. They were thought to be related to the pipefish and seahorses but are now thought to be more closel ...

s and small frogs. To avoid predation by birds, the raft spider can fully submerge itself in water and has been known to hide underwater for several minutes. As is the case with some other ''

'' species'', Dolomedes fimbriatus'' is sexually cannibalistic, meaning that the female will sometimes eat the male before, during or immediately after mating. Males will try to court the female and prevent her from attacking by signalling their presence using vibrations on the female

dragline A dragline excavator is a piece of heavy equipment used in civil engineering and surface mining. Draglines fall into two broad categories: those that are based on standard, lifting cranes, and the heavy units which have to be built on-site. Mo ...

. However, ''Dolomedes fimbriatus'' is one of the few species known to attempt to attack nearly all approaching males. This behaviour is regarded as unusual among biologists as it can prevent both the male and the female from copulating successfully. If successful copulation takes place, the female will carry her fertilised egg sac around with her, before placing the egg sac inside a silken nursery tent that she has made. The female will then guard the nursery until the

lings are ready to disperse into the surrounding habitat. JuvenileFimbriatus.jpg, Juvenile raft spider Dolomedes fimbriatus 720x576.ogv, ''Dolomedes fimbriatus'' (video) Raft spider (Dolomedes fimbriatus) female.jpg, Female raft spider carrying egg sack Juvenile Dolomedes fimbriatus.jpg, Juvenile Dolomedes fimbriatus

References

External links

* *
Raft spider at Digital Wildlife
{{Taxonbar, from=Q847066 Articles containing video clips Dolomedes Spiders of Asia Spiders of Europe

Habitat and description

Behaviour

References

Further reading

External links