Other Common Names
Dark Fishing Spider (Schwartz et al., 2013)
Synonyms and other taxonomic changes
Dolomedes tenebrosus Hentz, 1844
for synonyms, see the
World Spider Catalog.
Size
body length of female 15-26 mm, of male, 7-13 mm
Identification
Brownish to gray with few white marks, dark W-shaped marks on dorsal surface of abdomen. Note that mature females are much larger than mature males--see Life Cycle.
The main difference between scriptus and tenebrosus is that the 'W' pattern on scriptus is outlined in white all the way across the abdomen. The pattern in tenebrosus is broken.. and it generally has less white. It also appears that scriptus has a fuller and more complete median carapace stripe.
Dolomedes scriptus
Dolomedes tenebrosus
Additionally
Dolomedes tenebrosus features an inverted "v shaped" black mark beginning at the AME extending to the edge of the clypeus enclosing a light spot on the anteromedial margin compared to
Dolomedes scriptus which is dark only around each eye with a homogenous medium gray clypeus
(1):
Dolomedes scriptus
Dolomedes tenebrosus
Epigynum:
Palp:
Range
Eastern North America: southeastern Canada south to Florida, west to North Dakota, Texas.
Habitat
Bushes, rocks, etc., near permanent bodies of water, sometimes in dry woodlands. D. tenebrosus is the Dolomedes species most commonly found in human dwellings.
Juveniles are often found sitting on large leaves
Life Cycle
The male of this species always dies during mating (Schwartz et al., 2013). There is extreme sexual dimorphism and divergence in life histories. Quoting Schwartz et al., with references removed:
While females and males of most Dolomedes species are similarly sized, D. tenebrosus exhibits extreme female-biased sexual size dimorphism: females weigh 14 times more than males and have cephalothoraxes that are 2.5 times as wide. Like many spiders, D. tenebrosus live for 1–2 years, but the sexes appear to have different life-history strategies. Of hundreds of juveniles collected in the field and reared in the laboratory over a 4-year period, males always matured the same season, whereas females took an additional year to mature. Additionally, within a season, males mature earlier than females.
A YouTube video of the male and female mating can be seen
here.
Print References
Howell and Jenkins, pp. 224-225, fig. 137
(2)
Kaston, p. 179, fig. 451
(3)
Carico, J. E., 1973. The Nearctic species of the genus Dolomedes (Araneae: Pisauridae). Bulletin Museum of Comparative Zoology Harvard 144: 435-488. (
Species Description Here)
Schwartz SK, Wagner WE Jr, Hebets EA. Spontaneous male death and monogyny in the dark fishing spider. Biol Lett. 2013 Jun 19;9(4):20130113. doi: 10.1098/rsbl.2013.0113. PMID: 23784928; PMCID:
PMC3730621.
