The raft spider, scientific name ''Dolomedes fimbriatus'', is a large semi-aquatic
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
of the family
Dolomedidae
Dolomedidae is a family of spiders comprising seven genera formerly part of the family Pisauridae. It includes the genus '' Dolomedes'', known commonly as raft spiders, and its close relatives.
Taxonomy
The family was first circumscribed by Eug ...
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 Dolomedidae. 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, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
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 compr ...
'' 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 International_Code_of_Zoological_Nomenclature, 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 spe ...
of its genus.
Behaviour
Like many other species of the genus ''
Dolomedes
''Dolomedes'' is a genus of large spiders of the family Dolomedidae. 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 ...
'' (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 animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s such as water beetles,
pond striders and dragonfly larvae, but they occasionally feed on small
vertebrate
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain.
The vertebrates make up the subphylum Vertebra ...
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 close ...
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 ''
Dolomedes
''Dolomedes'' is a genus of large spiders of the family Dolomedidae. 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 ...
'' 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 heavy-duty excavator used in civil engineering and surface mining. It was invented in 1904, and presented an immediate challenge to the steam shovel and its diesel and electric powered descendant, the power shovel. ...
.
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
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
lings are ready to disperse into the surrounding habitat.
References
Further reading
*
External links
*
*
Raft spider at Digital Wildlife
{{Taxonbar, from=Q847066
Articles containing video clips
Dolomedes
Spiders of Asia
Spiders of Europe