*Whitebanded fishing spider (Dolomedes albineus), Cedar Park, Texas
Report and Photographs Courtesy of Carla E., 31 July 2007
Hi---This was in my friend's back yard in mid July, 2007. I don't have any measurements (she was a little freaked out) but it was a large spider. Identity? Thanks, Carla [Editor's Note: Carla later wrote that the spider's body was 1.5 inches long. Cedar Park, Texas, is north-northwest of Austin, on U.S. Highway 183] .
Editor's Notes: This large, extraordinarily beautiful spider (the body was reported to be 1.5 inches in length, and the photographer was quite shaken by its appearance) was not immediately identified to species. It appeared, to me, to be a nursery web spider in the family Pisauridae, a member of the genus Dolomedes (known collectively as fishing spiders, comprised mostly of aquatic species, along with a few terrestrials and arboreals). It is good to be cautious when identifying unusual spiders from photographs alone. A great number of arabesque orbweavers (Neoscona arabesca) have been--methinks--erroneously identified on a number of Internet pages as barn orbweavers (Araneus cavaticus), the species that inspired E. B. White to write his children's book "Charlotte's Web". One wonders how so many mistaken identities could have occurred. Are they due to the former's hairy, ugly appearance (consistent with the way many authorities describe Araneus cavaticus)? Or--just as likely--can the majority of those erors be traced back to a single instance, on a much-viewed website, where a Neoscona arabesca was misidentified as Araneus cavaticus? It is incumbent on the analyst to use care. I try to take pains not to violate that rule...
After reviewing much literature on the Pisauridae, I feel confident that it is what many amateur arachnologists classify as a whitebanded fishing spider (Dolomedes albineus). One reason for this confidence is that it does not fit the descriptions of any of the other eight species of Dolomedes found in the United States, but is reasonably similar to the description of Dolomedes albineus. That's the best I could do, but inasmuch as so primitive a procedure has worked well for me in the past, I feel emboldened to use it here as well. A large size is characteristic of the Pisauridae, and the arrangement of the eyes is consistent with that taxonomical placement. Furthermore, the architecture of the carapace is what one would expect of a Dolomedes.
It is not a wolf spider, as the posterior median eyes (PME) in the middle of the blackened dorsal face shown below, are too small (they appear similar in size to, or slightly larger than, the posterior lateral eyes, PLE, further out to the side at the posterior margin of the black facial marking; the Lycosid's PME are, by contrast, considerably larger than its PLE and face forward, not upward as with this fellow. Note how the anterior margin of the face forms a sharply delineated straight line along the dark facial marking, then projects slightly forward laterally; these features are characteristic of the Dolomedes. Notice also that the cephalic grooves (the lines of demarcation on each side, between the head and thorax) curve gently around the posterior head, meeting behind the head, at the center of the cephalothorax, to form a tongue-like formation at the anterior thoracic furrow. That tongue-like formation is common to most Dolomedes, though it is muted in Dolomedes triton and Dolomedes tenebrosus, pronounced in Dolomedes vittatus, and somewhere between those extremes for Dolomedes albineus.
The small, leg-like structures projecting out from each side of the head, and positioned with their tips forward of the head, have remarkably swollen tips. These structures are pedipalps, which in the female are fitted with ordinary tips, but in the male are greatly enlarged at their extremities with emboli used during mating. Hence the firm conclusion that this is a male. Note the extraordinary covering of hairs, on all body parts including the legs. Such pubescence seems unusual for an aquatic fishing spider, leading me to think, early on, that this a terrestrial species. Dolomedes albineus is, indeed, arboreal.
When the carapace of this spider is viewed with the head pointed downward, it appears to resemble the face of a cow. Click on the link, above, for a look.
Only nine species of Dolomedes have been identified in the United States, though additional species are found in Mexico and Central America. When I first pored over photos of each of the nine identified U.S. species, I failed to find anything resembling this specimen, though it did resemble the gross features of Dolomedes albineus. Later, in several other sources, I found images of the whitebanded fishing spider that had many of the features of this specimen. It is not unusual for single specimens of spiders (and of snakes as well) to show variations in markings and coloration that vary significantly from others of their species.
*Note: The common name of this spider is not listed in the authoritative "Common Names of Arachnids, Fifth Ed., 2003", published by the American Arachnological Society Committee on Common Names of Arachnids, R. G. Breene, Chairman. However, it appears to conform to the guidelines of that document, is frequently applied by amateur arachnologists to the species, seems reasonably descriptive thereof, and appears unlikely to lead to undue confusion with arachnids having similar common names, e.g., the whitebanded crab spider (Misumenoides formosipes Walckenaer), and the whitebanded tarantula (Acanthoscurria geniculata C.L. Koch). In the Nearctic Spider Database, published in the Canadian Arachnologist, a publication of Department of Biological Sciences, University of Alberta, Edmonton, Alberta, the common name of this species is listed as "none". In a personal communication Dr. Breene on 12 August 2007 suggested that whitebanded fishing spider was an appropriate common name for this species, but mentioned that the American Arachnological Society Committee on Common Names of Arachnids has not yet added it to their list. Dr. Breene also mentioned that he has retired from the chair of that committee, and his replacement has not yet been selected.
Many thanks to Carla for this excellent photo!!!
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