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A Male Wolf Spider in College Station, Texas

This article by Jerry Cates and Sarah A. Woller, first published on 25 November 2012, was last revised on 18 January 2013. © Bugsinthenews Vol. 13:11(05).

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Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Dorsal Habitus

001. Dorsal habitus

On 24 November 2012 Sarah A. Woller, of the Texas A&M Institute for Neuroscience, Department of Psychology, wrote that she had taken some photos of a wolf spider, and that while the spider was in captivity it exuded a mucus-like material that covered much of its abdomen. Would I like copies of the photos?

Sarah, an outstanding photographer, had already sent me a number of excellent images, all of which I hope to post on bugsinthenews soon. I knew the products of her photographic labors would almost certainly be of extraordinary quality, and that led to an immediate reply in the affirmative. Not that I insist on using only high quality images here. Mediocre, even poor photos of important organisms make worthy postings if they are the best to be had. My latest micrograms, for example — which prove that shooting good photos through a dissecting microscope lens is an art I’ve yet to master — testify to that. But I digress…

The three photos Sarah sent of her wolf spider are posted here. Because of their high resolution (she took them with a Nikon D3200, a 24.2 megapixel DX format DSLR F-mount camera that Nikon officially launched on April 19, 2012) it was possible to select portions of each for enlargement to show closeups of important anatomical features.

About this specimen…

As mentioned in my previous articles on the Lycosidae, identifying a wolf spider to genus and species is — at least for me — a difficult thing to do. Unless, of course, the specimen is adorned with a unique, easily recognized marking of some kind. The rabid wolf (Rabidosa rabida), for example, is no trouble at all, as are all the other species in that genus (thanks to Brady & McKinley, 1994). Alas, however, that’s the exception most of the time, primarily because the common wolf spider one happens upon in the field — one, for example, such as Sarah’s specimen — is usually clad in such ho-hum colors and pedestrian markings as to make it appear, to the uninitiated, much like all the other wolf spiders one encounters.

I confess, with a tinge of shame, to being one of those “uninitiated.” But it pains me so to admit it that, given time to do so, I’ve intended to develop at least a modicum of expertise in the subject. This requires achieving an acceptable level of familiarity with the genera and species of the Lycosidae family, which according to Dondale (2005) in North America number 16 and 238 respectively. The threshold of an “acceptable level of familiarity” will be reached, methinks, when I can no longer honestly say “if you’ve seen one, you’ve seen them all.”

Well, that’s been my plan for some years now. The self-imposed pressure to move my plan forward has been building, albeit slowly. Now comes Sarah, with a set of beautiful photos that provide the last ounce of impetus needed to overcome the barriers of inertia. Analyzing them requires a careful comparison with the various genera into which the Lycosidae is divided. That alone, more than anything else, will be the purpose of this article, and much should be learned in the process. It is, of course, only a beginning, and a small one at that. Yet, as they say, it portends a journey of a thousand miles…

Let us begin by identifying this spider’s gender…

We know immediately, on looking at Sarah’s photos, that her spider is a male. The observations that the abdomen is much smaller than the cephalothorax, and that the legs are decidedly longer than the body, suggest this, according to B. J. Kaston, on page 18 of his seminal book, How to know the spiders (The Pictured key nature series). But the most important distinguishing feature in this regard, for most araneid arachnids (i.e., spiders, as distinguished from ticks, mites, scorpions, harvestmen, and solpugids, all of which are non-araneid arachnids) is the morphology, i.e., the form, of their palps. A spider’s palps consist of a pair of diminutive leg-like appendages that stretch outward from its face. While similar to true legs, palps lack the latter’s next to last segment, the metatarsus. Female palps appear identical to true legs in all respects save that missing segment, and are employed in rather mundane tasks such as palpating an article of food prior to its consumption. Not so in the male, for that gender’s palpal tarsi (the terminal segments) serve as organs of sperm storage preparatory to, and of intromission during, copulation, besides being used as signalling devices during courtship.

If you presume that, in order to perform these crucial masculine functions well, extraordinary architectural modifications would have to have been made to the male palpal tarsi, you are correct. Typical modifications involve not only their diametrical expansion, making them appear swollen, but also the introduction of intricate internal and external structures, the precise arrangement and design of which vary widely within families and genera, and — though less so — between species within a generic grouping.

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Frontal Habitus

002. Frontal habitus

Notice that the distal ends of the palps of Sarah’s specimen have a larger diameter than the preceding proximal segments; that’s a strong clue that this spider is of the male gender. Fig. 001 shows this well, and fig. 104 provides an enlargement of the portion of that photograph that includes the right palp, with its ventral (underneath) and retrolateral (posterior) surfaces in view. Unfortunately, because the palps are not in sharp focus, we cannot discern the details of the palpal structure beyond these meager points.

The epigastric furrow…

Fig. 107 depicts the spider’s ventral abdomen. Click on the photo to enlarge it. Then notice the thin dark line that appears to divide the abdomen, laterally, about one fourth the distance from the sternum (the shield-like area in the upper right corner of the photo) to the spinnerets (the darkened structures at the very tip of the posterior abdomen). The thinner portions of this line, on the sides, are lung slits through which air is drawn into and expelled out of the spider’s internal book lungs; the sclerotized covers over the book lungs are, in this specimen, paler than the surrounding portions of the abdomen, and here divide the abdomen, anterior of the lung slits, into three sections; the left and right book lungs themselves, and an unsclerotized area between them. At the middle third of this dark line, anterior of the unsclerotized area between the book lungs, it becomes darker, revealing the epigastric furrow. For a thorough discussion on this, you may wish to read Rainer Foelix’s excellent book, Biology of Spiders, but it is here through which, in the male, sperm produced in the testes is released to the outside preparatory to mating. Were this a female, her eggs would be released from the ovaries through this furrow after fertilization; further, the unsclerotized area between her book lungs would include an epigynum which, in entelegyne spiders such as the Lycosidae, is itself sclerotized and of a very distinct architecture that, like the male’s palps, varies from one genus to the next and thus is diagnostic of the genus to which the spider belongs.

Recall that Sarah mentioned this spider exuding a mucous-like material that covered a portion of its abdomen. She kept the spider for several days and it appeared healthy when she released it into the wild, so the exudate she saw early on was not a sign of trauma or her spider would likely have expired. Most likely, then, it was sperm that the spider had exuded preparatory to mating. Male spiders eject their sperm into a sperm web that is produced from silk glands lining the anterior edge of the epigastric furrow; they then dip their palps into the sperm web to charge them with its contents. The walls of the male palps of entelegyne spiders such as the Lycosidae have a complex mixture of sclerotized parts (sclerites) and resilient, softer, inflatable areas (hematodochae), both of which often bear special protrusions or apophyses, whose architectures figure significantly in the copulatory process.

What makes it a wolf spider?

What enables us to distinguish this specimen as a “wolf” spider, i.e., a member of the Lycosidae family, is the number and arrangement of its eyes. Fig. 002 provides Sarah’s image of the spider facing the camera, and fig. 105 is an enlargement of the face from that photo. Notice first that this spider has a total of eight eyes. All lycosids, as well as many other spiders, are so provisioned, but none has eyes arranged quite like those of the Lycosidae.

In the Lycosidae four small, subequal eyes form a distinct row (the AER, or anterior eye row) directly above the jaws, with two much larger eyes (the PME, or posterior median eyes) directly above them. Two more eyes (the PLE, or posterior lateral eyes), also larger than those of the small row, (together forming the PER, or posterior eye row) spaced further back on the carapace so that these four larger eyes form a quadrangle that appears as two separate eye rows (but with an appreciation of arachnid anatomy is properly seen as the four eyes of the PER). Only the lycosids have this general eye arrangement. The Pisauridae (nursery web spiders) come close, but for them the PER is not spaced far enough back on the carapace to give the illusion of forming two separate eye rows.

Identifying this specimen to genus and species…

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All photos provided in this and in other articles posted on bugsinthenews may be enlarged for more detailed viewing by hovering your cursor over the photo and clicking.

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Note (fig. 105) that the four smallest eyes of the AER are not exactly the same size: the ALE (anterior lateral eyes) are smaller than the AME (anterior median eyes). Further, though they describe a generally horizontal row, in this spider the row is not straight, but is procurved (each ALE is anterior of the adjacent AME). Also, though the eyes in the AER are not the same size, they appear at first glance to be about the same distance from one another across the row (this observation, however, deserves closer scrutiny).

Lycosids in the genus Trochosa have a recurved AER (the AME are anterior of the ALE); though the markings of the anterior carapace are reminiscent of the Trochosa’s paired dark longitudinal streaks (found in the pale area anterior to the dorsal groove), they are not as prominent as those of the typical Trochosa, and the arrangement of the AER rules that genus out. Spiders in the genus Hesperocosa (1 species in North America, H. unica) have ALE that are larger in diameter than their AME.  Note that in fig. 105 the ALE do not appear to be situated on small tubercles, though they are not exactly flush with the carapace; fig. 106 provides another view from underneath which lends no support to the ALE having underlying tubercular foundations; this seems to rule out the six species of spiders in the genus Sosippus. On the basis of these observations, then, we will tentatively exclude the Trochosa, Hesperocosa, and Sosippus from further consideration.

Fig. 108 shows the ventral tibia of the spider’s right legs, I and II (the first and second legs, counting from the anterior of the spider’s body backward). Note that each tibia has exactly three pairs of macrosetae (pointed, rigid spines, situated in sockets and capable of articulating). Lycosids in the genera Trabeops and Pardosa, and one species in the genus Pirata (P. spiniger), have additional pairs of macrosetae here. 28 other species in the genus Pirata have a v-shaped mark, on the anterior carapace, which is lacking in this specimen; one additional species in the genus Pirata (P. bryantae), though having the three pairs of macrosetae shown in fig. 108, is distinguished by having a totally black carapace, abdomen, and legs I and II. On the basis of these observations we will tentatively drop the genera Trabeops, Pardosa, and Pirata from contention.

Fig. 101 shows the ventral habitus of Sarah’s specimen. Note that the underside of this spider is pale in color. The ventral cephalothorax of some spiders in the genus Hogna is solid black. However, that is true only for some of the 25 species in this genus. The Hogna ALE is either smaller than or equal to, but never larger than, the AME, consistent with Sarah’s specimen.

Fig. 102 shows clearly that this specimen has a pubescent carapace, vs. the generally glabrous carapaces of lycosids in the genus Arctosa as well as those in the genus Allocosa. Exceptions to this “rule” abound, however, so we must be careful.

More to come…

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Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Frontal Habitus

100. Frontal habitus

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Ventral Habitus

101. Ventral habitus

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Carapace

102. Carapace

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Dorsal body

103. Dorsal body

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Right palp

104. Right palp

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Frontal face

105. Face

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Ventral mouthparts

106. Ventral mouthparts

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Ventral abdomen

107. Ventral abdomen

Male Lycosidae; Sarah A. Woller, College Station, TX, 24 Nov 2012 --- Ventral tibiae, right legs I & II

108. Ventral tibiae, RL I & II

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Taxonomy:

  • Kingdom Animalia (an-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 1778), using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
  • Phylum Arthropoda (ahr-THROPP-uh-duh) first described in 1829 by the French zoologist Pierre André Latreille [November 20, 1762 – February 6, 1833], using the two Greek roots αρθρον (AR-thron) = jointed + ποδ (pawd) = foot, in an obvious reference to animals with jointed feet, but in the more narrow context of the invertebrates, which have segmented bodies as well as jointed appendages;
  • Subphylum Chelicerata (Kuh-liss-uh-RAH-tah) — first described in 1901 by the German zoologist Richard Heymons [1867 - 1943] using the Greek noun χηλη (KEY-lay) = a claw, talon, or hoof + the Greek noun κερας (Ser-as) = an animal’s horn + the Latin suffix ata — which by convention is suffixed to the names of animal subdivisions — to refer to animals that have specialized appendages before the mouth that they use in feeding, capturing and securing prey and that — in the case of spiders — are further equipped to inject venom and digestive agents into their prey; 
  • Class Arachnida (uh-RAKH-nuh-duh) first described in 1812 by the French naturalist and zoologist Jean Léopold Nicolas Frédéric Cuvier [August 23, 1769 – May 13, 1832], usually referred to as Georges Cuvier, using the Greek noun αραχης (uh-RAH-kes) = a spider, in reference to all eight-legged arthropods, including such disparate animals as ticks, mites, scorpions, harvestmen, solpugids, and spiders;
  • Order Araneae (uh-RAY-neh-ee) — first described in 1757 by the Swedish entomologist and arachnologist Carl Alexander Clerck [1709 – 22 July 1765], who used the Latin word aranea = a spider or a spider’s web, to refer to eight legged arthropods that spin webs;
  • Suborder Opisthothelae (oh-PIS-thoh-THEE-lee) — first described in 1990 by the American arachnologists Richard C. Brusca and Gary J. Brusca, who used the Greek words οπισθεν (oh-PIS-thehn) = behind, at the back, yet to come + θηλη (THEE-lee) = nipple or teat, to distinguish this grouping of spiders from the more primitive spiders in the suborder Mesothelae, in that certain characters (e.g., tergite plates, ganglia in the abdomen, and — in particular, inasmuch as the suborder name is a direct reference thereto — median-positioned spinnerets) of the latter are absent in the former; thus spiders in this suborder have spinnerets positioned at the hindmost portion of the abdomen;
  • Infraorder Araneomorphae (Uh-RAY-nee-oh-MOHR-fee) — distinguished from the mygalomorphae by having opposing fangs that open and close perpendicular to the spider body’s longitudinal axis, in a pinching action, whereas spiders in the infraorder mygalomorphae (e.g., tarantulas and trapdoor spiders) have fangs that open and close more nearly in alignment with the spider body’s longitudinal axis;
  • Series Entelegynae (inn-TELL-uh-jiy-nee) — araneomorph spiders which, unlike the Haplogynae, have hardened, i.e., sclerotized, female genitalia. Foelix (2011) points out that “entelegyne spiders have more complex reproductive organs (with an epigyne and separate fertilization ducts in the female)…” and that “Male entelegyne genitalia are very diverse…“;
  • Superfamily Lycosoidea (lye-koh-SOY-dee-uh) — a superfamily of eight-eyed entelegyne araneomorph spiders comprised of 11 families, 291 genera, and 4,191 species (Platnick 2012a, in the AMNH World Spider Catalog, version 13.5):
    • Family Lycosidae (Sundevall, 1833) — 120 genera, 2,393 species (Platnick 2012a; #69 in WSCv13.5; 5 species added since v13.0); commonly known as wolf spiders;
    • Family Trechaleidae (Simon, 1890) — 16 genera, 119 species (Platnick 2012a; #70 in WSCv13.5; 1 species added since v13.0); found in Central and South America;
    • Family Pisauridae (Simon, 1890) — 48 genera, 331 species (Platnick 2012a; #71 in WSCv13.5; reduced by one genus since v13.0); commonly known as nursery web spiders;
    • Family Oxyopidae (Thorell, 1870) — 9 genera, 444 species (Platnick 2012a; #72 in WSCv13.5; 11 species added since v13.0); commonly known as lynx spiders;
    • Family Senoculidae (Simon, 1890) — 1 genus, 31 species (Platnick 2012a; #73 in WSCv13.5; unchanged from v13.0); bark-hunter spiders found only in Central and South America;
    • Family Stiphidiidae (Dalmas, 1970) — 22 genera, 135 species (Platnick 2012a; #74 in WSCv13.5; unchanged from v13.0); tent-web spiders found in Australia, New Zealand, and Mauritius;
    • Family Zorocratidae (Dahl, 1913) — 5 genera, 42 species (Platnick 2012a; #75 in WSCv13.0; unchanged from v13.0); a little known family of hunting spiders;
    • Family Psechridae (James, 1989) — 2 genera, 51 species (Platnick 2012a; #76 in WSCv13.5; unchanged from v13.0); lowland funnel-web spiders found only in Southeast Asia;
    • Family Zoropsidae (Bertkau, 1882) — 14 genera, 86 species (Platnick 2012a; #77 in WSCv13.5; unchanged from v13.0); commonly known as false wolf spiders, native to Australia and South Africa, with one species (Zoropsis spinimana) introduced into North America, now found in homes in the San Francisco bay area;
    • Family Zoridae (F. O. P.-Cambridge, 1893) — 14 genera, 79 species (Platnick 2012a; #78 in WSCv13.5; number of genera and species unchanged from v13.0, but other changes were made to the file); mostly tropical spiders that hunt without webs;
    • Family Ctenidae (Keyserling, 1877) — 40 genera, 480 species (Platnick 2012a; #79 in WSCv13.5; 12 species added since v13.0); commonly known as wandering spiders;
  • Family Lycosidae (lye-KOH-suh-dee) —  first described in 1833 by the Swedish zoologist Carl Jakob Sundevall (1801-1875), who chose the Greek word λύκος (LYE-kos) = wolf, as a reference to the way wolves hunt for and take down their prey, though wolves hunt in packs and the arachnids Sundevall had in mind hunt alone; the spiders in this family are small to large (2.2-35.0 mm) hunting spiders with a distinctive eye arrangement: the anterior eye row (AER) is composed of four small, similarly sized eyes arranged frontally in a line across the front of the carapace just above the clypeus; the posterior eye row (PER) is composed of much larger eyes, such that the posterior median eyes (PME) are arranged frontally, just above the AER, with the posterior lateral eyes (PLE) positioned dorsally, posterior to, generally wider apart than, and forming a quadrangle with, the PME; the egg sac, or cocoon, is carried by the female attached to the spinnerets; when the spiderlings emerge from the egg sac they migrate to the female’s dorsum, where they remain for several days before dispersing; Lycosids come in tan, light brown, to dark charcoal brown background colors, with pale, cream, white, black, yellow or red markings. The carapace and/or abdomen may be boldly or vaguely marked with two or more longitudinal stripes. Legs are long and stout, and are often supplied with dense scopulae; the tarsi have three claws. Vision is used to detect, stalk, and ambush prey in a variety of habitats; this family is comprised, worldwide, of more than 100 genera, of which 16, grouped in four subfamilies and two groups, are known to be represented in North America:
    • Subfamily Sosippinae: Genus Sosippus (Simon 1888) — ALE on small tubercles; spiders live on a funnel web;
    • Subfamily Venoniinae:
      • Genus Pirata (Sundevall 1833) — One species (P. spiniger) has more than 3 pairs of macrosetae on the ventral tibiae of legs I & II; 28 species have a conspicuous v-shaped mark on the anterior carapace; one species (P. bryantae), though having the three pairs of macrosetae on the ventral tibiae of legs I & II, has a totally black carapace, abdomen, and legs I and II;
      • Genus Trabeops (Roewer, 1959) —Ventral tibiae I & II with more than 3 pairs of macrosetae;
      • Genus Trebacosa (Dondale & Redner, 1981) —
    • Subfamily Allocosinae: Genus Allocosa (Banks, 1900) — Generally glabrous carapace;
    • Subfamily Pardosinae:
      • Genus Acantholycosa (Dahl, 1908) —
      • Genus Pardosa (C. L. Koch, 1847) — Ventral tibiae I & II with more than 3 pairs of macrosetae;
    • Group Lycosinae-Lycosa:
      • Genus Alopecosa (Simon, 1885) —
      • Genus Arctosa (C. L. Koch, 1847) — Generally glabrous carapace;
      • Genus Lycosa (Latrielle, 1804) —
      • Genus Melocosa (Gertsch, 1937) —
      • Genus Paratrochosina (Roewer, 1960) —
      • Genus Varacosa (Chamberlin & Ivie, 1942) —
    • Group Lycosinae-Trochosa:
      • Genus Geolycosa (Montgomery, 1904) — Burrowing spiders, lacking dorsal spines on the posterior tibiae in females, but present in males; the cephalothorax viewed laterally is very high in head region, sloping steeply to the pedicel; retromargin of cheliceral fang furrow bears three teeth; females plain grayish to bluish-gray; males with middorsal white stripe on head bordered by black stripe either side, and a black middorsal stripe bordered by white stripe either side on abdomen; females 18-22mm, males 14-16mm;
      • Genus Gladicosa Brady, 1987 —
      • Genus Hesperocosa (Gertsch & Wallace, 1937) — 1 N.A. species (H. unica); ALE larger than AME;
      • Genus Hogna (Simon, 1885) —
      • Genus Tigrosa Brady, 2012 —  5 nearctic species, including 4 species transferred from the genus Hogna (Simon, 1885), and 1 species transferred from the genus Allocosa Banks 1900;
      • Genus Rabidosa (Roewer, 1960) —
      • Genus Schizocosa (Chamberlain, 1904) —
      • Genus Trochosa (C. L. Koch, 1847) — AER recurved; paired dark longitudinal streaks in pale area anterior to dorsal groove;

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References:

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— Questions? Comments? Corrections? e-mail jerry.cates@bugsinthenews.info. You may also register, log in, and leave a detailed comment in the space provided below.



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