{{Short description|Species of spider}} {{Speciesbox | name = Raft spider | image = AttackPosition.jpg | image_caption = Raft spider attack position | taxon = Dolomedes fimbriatus | authority = (Clerck, 1757)<ref name=WSC_s27290/> | range_map = Distribution.dolomedes.fimbriatus.1.png | synonyms = ''Araneus fimbriatus'' Clerck, 1757 | synonyms_ref = <ref name=WSC_s27290/> }}
The '''raft spider''' (''Dolomedes fimbriatus'') is a large semi-aquatic spider of the family Dolomedidae found throughout north-western and central Europe.<ref>{{Cite web|url=http://srs.britishspiders.org.uk/portal.php/p/Summary/s/Dolomedes+fimbriatus|title=Summary for Dolomedes fimbriatus (Araneae)|website=srs.britishspiders.org.uk|access-date=2019-03-01}}</ref> It is one of only two species of the genus ''Dolomedes'' found in Europe, the other being the slightly larger ''Dolomedes'' ''plantarius'' which is endangered in the UK.<ref>{{Cite web|url=https://www.dolomedes.org.uk/homepage|title=Welcome to the web site dedicated to the fen raft spider {{!}} Dolomedes.org.uk|website=www.dolomedes.org.uk|access-date=2019-03-02}}</ref>
== Habitat and description == thumb|Juvenile raft spider
Raft spiders are semi-aquatic and adults inhabit freshwater wetlands, specifically wet heaths and acid swamps;<ref name=":1">{{Cite web|url=https://www.dolomedes.org.uk/drupal/index.php/index.html?q=biology/index.html|title=Biology {{!}} Dolomedes.org.uk|website=www.dolomedes.org.uk|access-date=2019-03-02}}</ref> although juveniles are predominantly found in terrestrial vegetation surrounding wetland areas.<ref name=":1" /> 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).<ref>{{Cite web|url=https://araneae.nmbe.ch/data/411/Dolomedes_fimbriatus|title=araneae - Dolomedes fimbriatus|website=araneae.nmbe.ch|language=en|access-date=2019-03-01}}</ref> Dolomedes fimbriatus was described in chapter 5 of the book ''Svenska Spindlar'' by the Swedish arachnologist and entomologist Carl Alexander Clerck. It is the type species of its genus.
== Behaviour == Like many other species of the genus ''Dolomedes'' (Greek translation= crafty or wily),<ref>{{Cite book|title=Svenska Spindlar|last=Clerck|first=Carl Alexander|year=1757|location=Sweden}}</ref> the raft spider typically hunts on the surface of the water with its front appendages outstretched and relies on aquatic vibrations to detect prey.<ref>{{Cite journal|date=1984|title=Sensory ecology of a semi-aquatic spider (Dolomedes triton)|journal=Behavioral Ecology and Sociobiology|doi=10.1007/bf00299501 |last1=Bleckmann |first1=Horst |last2=Rovner |first2=Jerome S. |volume=14 |issue=4 |pages=297–301 |s2cid=1893217 }}</ref> Juveniles are thought mainly to hunt in terrestrial vegetation.<ref name=":0">{{Cite web|url=http://www.uksafari.com/raftspider.htm|title=Raft Spiders - Dolomedes fimbriatus - UK Safari|website=www.uksafari.com|access-date=2019-03-01}}</ref> Their diet consists largely of freshwater invertebrates such as water beetles, pond striders and dragonfly larvae, but they occasionally feed on small vertebrates such as sticklebacks and small frogs.<ref name=":1" /> To avoid predation by birds, the raft spider can fully submerge itself in water and has been known to hide underwater for several minutes.<ref name=":0" />
As is the case with some other ''Dolomedes'' species'', Dolomedes fimbriatus'' is sexually cannibalistic, meaning that the female will sometimes eat the male before, during or immediately after mating.<ref>{{Cite journal|date=1992|title=Courtship Behavior and Sexual Cannibalism in the Semi-Aquatic Fishing Spider, Dolomedes fimbriatus (Clerck) (Araneae: Pisauridae)|journal=The Journal of Arachnology}}</ref><ref>{{Cite journal|date=2005|title=Precopulatory sexual cannibalism in fishing spiders (Dolomedes triton): a role for behavioral syndromes|journal=Behavioral Ecology and Sociobiology|doi=10.1007/s00265-005-0943-5 |last1=Johnson |first1=J. Chadwick |last2=Sih |first2=Andrew |volume=58 |issue=4 |pages=390–396 |s2cid=20652406 }}</ref> Males will try to court the female and prevent her from attacking by signalling their presence using vibrations on the female dragline.<ref name=":2">{{Cite journal|date=2016|title=Mate choice and sexual size dimorphism, not personality, explain female aggression and sexual cannibalism in raft spiders|journal=Animal Behaviour|doi=10.1016/j.anbehav.2015.10.013 |last1=Kralj-Fišer |first1=Simona |last2=Čandek |first2=Klemen |last3=Lokovšek |first3=Tjaša |last4=Čelik |first4=Tatjana |last5=Cheng |first5=Ren-Chung |last6=Elgar |first6=Mark A. |last7=Kuntner |first7=Matjaž |volume=111 |pages=49–55 |s2cid=54282825 }}</ref> However, ''Dolomedes fimbriatus'' is one of the few species known to attempt to attack nearly all approaching males.<ref name=":2" /> This behaviour is regarded as unusual among biologists as it can prevent both the male and the female from copulating successfully.<ref>{{Cite journal|date=2018|title=Sexual cannibalism and population viability|journal=Ecology and Evolution}}</ref>
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 spiderlings are ready to disperse into the surrounding habitat.<ref>{{Cite web|url=https://www.dolomedes.org.uk/biology/life_history.html|title=Life history {{!}} Dolomedes.org.uk|website=www.dolomedes.org.uk|access-date=2019-03-02}}</ref>
<gallery> JuvenileFimbriatus.jpg|Juvenile raft spider Dolomedes fimbriatus 720x576.ogv|''Dolomedes fimbriatus'' (video) Raft spider (Dolomedes fimbriatus) female.jpg|Female raft spider carrying egg sac Juvenile Dolomedes fimbriatus.jpg|Juvenile Dolomedes fimbriatus
</gallery>
==References== {{Reflist|refs= <ref name=WSC_s27290>{{citation |title=Taxon details ''Dolomedes fimbriatus'' (Clerck, 1757) |work=World Spider Catalog |publisher=Natural History Museum Bern |url=http://www.wsc.nmbe.ch/species/27290 |access-date=2017-09-13 }}</ref> }}
==Further reading== *{{Cite journal | pages = 222–226 | last = Arnqvist | first = G. | title = Courtship behavior and sexual cannibalism in the semi-aquatic fishing spider, Dolomedes fimbriatus (Clerck)(Araneae: Pisauridae) | journal = Journal of Arachnology | date = 1992 | url = http://www.anst.uu.se/goarn789/ja%2092.pdf }}
==External links== * {{Wikispecies-inline}} * {{Commons category-inline|Dolomedes fimbriatus|''Dolomedes fimbriatus''}} * [http://www.digitalwildlife.co.uk/minibeasts/spiders/Raftspider.htm Raft spider at Digital Wildlife] {{Webarchive|url=https://web.archive.org/web/20100410150423/http://www.digitalwildlife.co.uk/minibeasts/spiders/Raftspider.htm |date=2010-04-10 }} *[https://web.archive.org/web/20081204151731/http://www.coldspringschool.org/Mill/raft.html Raft spider photos]
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Category:Articles containing video clips Category:Dolomedes Category:Spiders of Asia Category:Spiders of Europe