A Spitting spider from North Austin, Texas

BugsInTheNews is a VIEWER-PARTICIPANT WEBSITE. This article by Jerry Cates and Laura, first published in December 2008, was revised last on 27 November 2012. © Bugsinthenews Vol. 09:12

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Scytodidae: Spitting Spider (Sytodes thoracica); dorsofrontal view; Laura, Austin, TX--12.13.2008

001. Scytodidae: Spitting Spider (Scytodes); dorsofrontal view; Laura, Austin, TX--12.13.2008

Scytodidae: Spitting Spider (Sytodes thoracica); frontolateral view; Laura, Austin, TX--12.13.2008

002. Scytodidae: Spitting Spider (Scytodes); frontolateral view; Laura, Austin, TX--12.13.2008

A total of five genera and 228 species of spitting spiders, all in the Scytodidae family (first described by the British naturalist John Blackwall, in 1864), were recognized as of 31 December 2011 (Platnick 2012b). Thus, this relatively obscure family — which is one of 110 (0.91%) spider families recognized today — represents but 0.13 % of the genera, and 0.53 % of the species of all the world’s presently recognized spiders (3,859 genera, 42,751 species: Platnick 2012b).

Of the five Scytodidae genera, one (Scytodes, first described by the French zoologist Pierre André Latreille in 1804) and 7 of its species are known to be found in North America (Ubick, 2005).

Both the family and generic names are derived from the Greek stem σκυτωδης (skutodes) = “like leather,” a reference to the pattern of the markings on the dorsal carapace, which in some species resembles the mottled appearance of finely-tanned leather.

One species, Scytodes thoracica, a notorious synanthrope, is relatively common worldwide, as well as within the United States, though primarily in the eastern U.S. north to Canada (Ubick 2005).

Emerton (1902), who classed the genus Scytodes within the Theridiidae family (which at the time embraced many spiders now ensconced in separate families), mentions only S. thoracica in his account of the Scytodes, describing the species as a “very peculiar spider, probably imported from Europe, and found in cellars and closets.” He goes on to list its physical features, without any mention of its nocturnal predatory habits or its unusual chelicerae.

Comstock (1914), who listed the genus Scytodes with the recluse spiders of the Sicariidae family (the sicariids and scytodids are similar in many ways), states that, at the time, “only two species (in the genus Scytodes) have been observed in the United States.” He lists S. thoracica as being “not uncommon, even in the North, where it is found in cellars and closets” and S. longipes as being the larger of the two, found in the Antilles, in tropical South America, in Bermuda, and in Austin, Texas (where he personally collected specimens of the species). He reported that, in Bermuda, it is known as the dust spider; it moves slowly, he wrote, and is easily captured.

Kaston (1978) depicts in drawings and text, besides S. thoracica, the two species S. perfecta and S. fusca. Gertsch (1979) lists — in addition to S. thoracica (Latreille) — S. fusca (Walckenaer 1837), which Ubick (2005) describes along with S. longipes (Lucas 1844) as being pantropical and probably synanthropic, all of which are found in North America.

A Texas authority (Dean 2012) lists the following species, in addition to S. thoracica,  as being found in the Lone Star State:
2. Scytodes atlacoya (Rheims, Brescovit & Durán, 2007)
3. Scytodes dorothea (Gertsch, 1935)
4. Scytodes lugubris (Thorell, 1887),
5. Scytodes univittata (Simon, 1882), and
6. Scytodes zapatana (Gertsch & Mulaik, 1940).

At least two species of spitting spider found in Florida, while observed, have not yet been described, according to G. B. Edwards (pers. comm. from Edwards to Ubick 2005). Similar reports exist on spitting spiders in other parts of the U.S.

From the forgoing, one readily surmises that the Scytodidae family in North America, while subjected to much study in the past, is yet to be fully explored. This situation is not unusual, as many, if not most spider families in the U.S. await the rigorous and thorough collecting, cataloging, and preservation, not to mention the ensuing microscopic, and genomic analyses of the collected and preserved specimens, necessary to ensure the family has been fully documented.

Because the spitting spiders are so unique, in terms of the morphology of their venom glands and chelicerae, and their mode of predation, it is natural to expect them to have received more coverage in the media than ordinary spiders. However, such appears not to be the case.

The following examples illustrate the level of attention that spitting spiders receive in the popular scientific literature: One book on spiders and scorpions (Preston-Mafham, 1996) devotes two pages of cursory material to them. A recent book on the spiders of the eastern U.S. (Howell & Jenkins 2004), where these spiders are particularly common, devotes about three pages to them, and makes reference to one species, S. thoracica. A book on worldwide arachnids (Beccaloni 2009) discusses spitting spiders in in three sentences on one page and one paragraph on another. A detailed, 419-page treatise on spider biology (Foelix 2011) describes these spiders, and their unique mode of predation, in two short paragraphs and illustrations, with little of the detail that author otherwise provides on similarly arcane topics.

Fortunately, on proceeding beyond the popular literature to the peer-reviewed scientific papers written by arachnologists for their colleagues to read, one finds considerable, detailed material on the spitting spiders and their biology. The referenced links provided at the end of this article includes many of these papers, most of them available on-line to those interested in reading them.

Scytodidae: Scytodes: Left Frontodorsal Carapace; Laura, N. Austin --- 13 Dec 2008

100. Scytodidae: Scytodes: Left Frontodorsal Carapace; Laura, N. Austin --- 13 Dec 2008

Scytodidae: Scytodes: Left Frontodorsal Carapace; Megan P., S. Austin --- 12 Jan 2012

101. Scytodidae: Scytodes: Left Frontodorsal Carapace; Megan P., S. Austin --- 12 Jan 2012

The Megatherium Society is presently engaged in conducting a survey of North American spitting spiders (see the request for specimens, below). It is fitting that, inasmuch as Comstock, in his 1914 book, actually collected specimens of S. longipes in Austin, that the collection of Scytodidae specimens begin in that Texas city.

Photo 100 shows the carapace markings of Laura’s specimen, collected in north Austin, in December of 2008, compared, in photo 101, with those of a specimen collected by Megan P., in south Austin, on 12 January 2012. Note that the similarity of the markings for these two specimens is so  striking as to strongly suggest each represents the same species. The semi-educated guess would be that these are both S. thoracica, owing to the similarity of their markings, the boldest of which resemble the curved arms of a lyre. In an earlier version of this web page, Laura’s specimen was so identified, based on this superficial resemblance. Later that tentative identification was redacted, out of the realization that not enough care had been taken to exclude other possibilities.

The peculiar markings of the carapace characteristic of S. thoracica, as depicted by various authorities, differ somewhat from one drawing to the next, and none seem to show the markings of Laura’s specimen exactly. Also, a search of the literature for definitive images and/or drawings of S. longipes, S. atlacoya, S. dorothea, S. lugubris, S. univittata, and S. zapatana had not yet borne entirely satisfactory fruit. Then the fresh specimen from, from Megan P., in south Austin arrived, with marks identical to those of Laura’s.

Two arachnologists, Robert Suter (Vassar College) and Gail Stratton (University of Mississippi), have published a number of unusually detailed papers on the spiders in this family over the past ten years. Both were asked to comment on the possible identity of the two specimens pictured above. Dr. Suter’s remarks, received on 15 January 2012, are as follows:

The markings on your Scytodes are in the right pattern for S. thoracica and I’ve sometimes come across ones in which the dark parts are so black. That doesn’t necessarily mean anything.  S. thoracica has a wide range and can be expected to vary across it, and I don’t know what the characters are that allow species discrimination in the genus (they probably have to do with male palp and female epigynum details).

Dr. Suter pointed out, in a kindly way, the importance of studying the characters of the male palp and female epigynum. The Scytodidae, though, are haplogynes. Since the haplogyne epigynum is not sclerotized, the epigynal distinctions between species is less stark than would be the case for an entelegyne female. This presents irksome hurdles, particularly for a lazy microscopist like me who is always looking for the easy way out.

Unfortunately, none of the specimens obtained thus far have been males, whose distinctive palpal bulbs more readily assist in distinguishing between species. Suter’s subtle hint was not unexpected, as it mirrored that of Dr. Lehtinen (Turku University, Finland), a specialist in the Thomisidae, when I asked for help in identifying a crab spider found in Cameron, Texas. The lesson these scientists seek to press home is that genital characters are much more reliable keys to speciation than carapace markings. This means, quite simply, that we must be patient until additional specimens, including those of males, can be studied. Too bad. Analyzing carapace markings is much the easier of the two.

In the meantime, the epigynal characters of the female specimens in our possession need to be examined more closely, too. Yes, I know: laziness is no excuse.

Dr. Suter provided a link to a paper he co-authored with Gail Stratton which had not been included in the list of references at the end of this article. That 2009 paper, entitled “Spitting performance parameters and their biomechanical implications in the spitting spider, Scytodes thoracica,” was immediately added to the reference list.

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Request for Specimens:

An on-going study of spitting spiders in North America is being carried out under the auspices of the Megatherium Society. Multiple specimens of males and females of all North American species presently recognized in the genus Scytodes are being sought for microscopic analysis. It is possible that, in the process, additional species will be discovered, as studies suggest that several new N. A. species — yet to be described — have been observed in the past.

Those who collect specimens of spitting spiders for this project are asked to collect them alive if possible, singly (these spiders are notoriously cannibalistic), in plastic containers kept in a dark, cool place while arrangements are made (Call Jerry Cates at 512-331-1111) to have them picked up.

If the specimens are not alive, or if keeping live specimens for pickup is not an option, they should be preserved in pure ethanol (Everclear or equivalent, in preference to denatured ethyl or isopropyl rubbing alcohol) diluted with distilled water to a solution of 70-80% alcohol, in leakproof plastic vials. Such vials should be shipped to:

Megatherium Society Scytodidae Project
Attn: Jerry Cates
8411 Columbia Falls Drive
Round Rock, TX 78681

For more information please Telephone  Jerry directly at 512-331-1111, or e-mail jerry.cates@bugsinthenews.info.

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The specimen used to illustrate this species here is a tiny spider–it measures, from head to tail, about 4mm (3/16ths inch), long. It was collected by Laura, in north Austin, TX, on 12-13-2008, and appears to be an immature female, though it may be a male (until the penultimate stage [click here for an educational, amusing discourse on the meaning of penultimate], gender cannot be distinguished).

As an Emergency Medical Technician, Laura had a professional curiosity about the spiders around her, particularly those that might produce dangerous bites. She asked several of her fellow EMTs what kind they thought this spider was. When one told her it was a brown recluse, she became concerned.

She’d called me earlier this year about a snake, and decided to ask about the spider, too. I asked her to take some digital photos for me to examine, but when she had trouble getting her digital camera to focus on such a small critter, I offered to come by and pick it up. Later, at her home, without a magnifying glass (uncharacteristically, I’d left home without one), I guessed it might be a juvenile thin-legged wolf spider.

Back at the lab, under the microscope, its six eyes and convex dorsal cephalothorax quickly identified it as a spitting spider in the family Scytodidae.

As mentioned earlier, one of the more common species of spitting spiders found in North America is Scytodes thoracica, and Laura’s specimen appears to have similar markings to those of that species. None of the species in the genus Scytodes have been assigned a common name, so each is  simply referred to as a  spitting spider.

Two British arachnologists, L. Watson & J. Dallwitz (2004) report that this is the only species found in Britain (see the drawing provided, which is obviously taken from an early scientific treatise on the species, but for which no attribution is provided).

Scytodidae: Spitting Spider (Sytodes thoracica); eyes; Laura, Austin, TX--12.13.2008

200. Scytodidae: spitting spider (Scytodes); eyes; Laura, Austin, TX--12.13.2008

Scytodidae: Spitting Spider (Sytodes thoracica); Tarsal claw; Laura, Austin, TX--12.13.2008

201. Scytodidae: spitting spider (Scytodes); Tarsal claw; Laura, Austin, TX--12.13.2008

The spitting spiders are unique arachnids that squirt a glue-venom mixture from their chelicerae to ensnare and kill their prey, but they are considered harmless to humans and other mammals. (Ubick et al., 2005, p. 217-218).

For spiders in this family the tarsi of each leg has three claws. All three claws arise from a single cuticular platelet and cannot be articulated individually (Foelix 1996). By comparison, the Sicariidae have two claws (which, again, arise from a single cuticular platelet).

The middle claw of the spitting spider’s three claws is a hook, and is clearly shown in the photo, but its architecture is obscured by the poor quality of the imagery (mea culpa).

We can see from this photo, though, that the claws are essentially bare, without the profusion of hairs that many spiders have at the base of their claws. An absence of such tufts of hairs (known as scopulae) at the distal tarsus has important consequences.

This specimen, for example, was kept in a deep plastic dish, and Laura noted — with surprise — its inability to scale the smooth plastic walls. As Foelix (1996) pp. 19-21 points out, the scopulae permit spiders that possess them to climb smooth vertical walls of glass, but that faculty is denied spiders without these structures.

This same disability applies to the brown recluse, whose two-clawed tarsi are also without scopulae.

However, it should be pointed out that though spiders without scopulae (such as the spitting spiders and recluse spiders) cannot climb hard, smooth, vertical surfaces, they are quite able to use their tarsal claws to scale pliable, smooth, vertical surfaces, such as painted walls and hard plastic enclosures with miniscule mold seams. Furthermore, spiders in the Sicariidae and Scytodidae families have unusually long, spindly legs, which they are able to stretch to their full lengths as they palpate the walls of their confines in search of claw-holds. These are slow-moving spiders that tend to methodically examine every part of their environment, particularly when restricted to the bottom of an enclosure. If they are able thereby to find an attachment above them (such as a mold seam or an imperfection in an otherwise smooth surface) to latch onto, they will often manage, over time, to escape.

Though most spiders have eight eyes, those in the family Sytodidae have but six (the anterior median eyes, or AME, are absent), and their six eyes are arranged in three diads, or pairs. In the closeup image, the eyes of Laura’s specimen have a greenish cast, and are surrounded by a dark mask. One pair of eyes (the posterior median eye pair, or PME) faces forward, while the other pairs (the anterior and posterior lateral eyes, or ALE and PLE,  occupy a single diad) face to their respective sides.

This eye arrangement is almost identical to that of the Sicariidae family which, in North America, contains the genus Loxosceles (brown spiders, including the brown recluse). So, Laura’s friend was at least partially right. However, the brown spiders in the genus Loxosceles have a remarkably flat cephalothorax (the forward half of the spider’s body that includes the head and thorax), while that of the spitting spiders is remarkably convex, or domed.

Scytodidae: Spitting Spider (Sytodes thoracica); Ventral prosoma; Laura, Austin, TX--12.13.2008

202. Scytodidae: spitting spider (Scytodes); Ventral prosoma; Laura, Austin, TX--12.13.2008

Scytodidae: Spitting Spider (Sytodes thoracica); Ventral opisthosoma; Laura, Austin, TX--12.13.2008

203. Scytodidae: spitting spider (Scytodes); Ventral opisthosoma; Laura, Austin, TX--12.13.2008

Note that the sternum is convex and lightly marked, with few hairs, disposed below a large cephalothorax which at its posterior third extends outward the full length of coxae 3 and 4.

The palps (which, in the photo. appear as diminutive legs projecting forward of and on either side of the face) are absent any signs of a male sex organ, which in this genus consists of an obvious bulb with an embolus having a simple prong or more complicated projections.

The ventral opisthosoma (underside of abdomen) is remarkable for its absence of structures that typically quite visible on a spider’s ventral abdomen. Though they are not resolvable in this photo, six small, contiguous spinnerets are positioned on the posterior ventral abdomen. The lack of definition of these structures is most likely due to the fact this is an immature specimen whose morphology is undeveloped. When immature specimens like this are collected alive, it is best to rear them to maturity before conducting a full analysis of the body.

One pair of book lungs, positioned in the lateral ventral anterior abdomen, are hinted at by the light-colored areas in that portion of the image.

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Sytodidae: spitting spider (Sytodes spp.); habitus; Diana M., McAllen TX --- 10 Sept 2011

300. Scytodidae: spitting spider (Scytodes); habitus; Diana M., McAllen TX --- 10 Sept 2011

Note the image at left which is relatively indistinct yet provides sufficient detail to state with confidence this is not a recluse spider, as well as to make a better than good guess at the family it belongs to. On 10 September 2011, Diana M. wrote:

“Hi, I’ve attached a photo of a brown spider found in my kitchen. Would appreciate if you could ID it? The photo was taken at my home in McAllen, located in deep south Texas. “

The morphology of the prosoma (the anterior, or frontal division of the spider body, also known as the cephalothorax) is convex (bulbous), and highest in the thoracic region (the posterior portion). This character is rather unique, and is confined mostly to the Scytodidae family of spiders. When combined with the relatively long, smooth legs without conspicuous spines, the identification to this family is reasonably secure. As noted above, seven species are found in North America (Valerio, 1981, describes seven species from Central America in significant detail, though it is unclear if these are also the same seven species found further north), and it is not possible to assign this specimen to species from this photo.

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Taxonomy:

  • Kingdom Animalia (ahn-uh-MAYHL-yuh)  — first described in 1758 by the Swedish taxonomist Carolus Linnaeus [23 May 1707 – 10 January 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, in the mygalomorphae (e.g., tarantulas and trapdoor spiders), which have fangs that open and close more nearly in alignment with the spider body’s longitudinal axis.
  • Series Haplogynae (HAPP-loh-jiy-nee) — araneomorph spiders which, unlike the Entelegynae, lack hardened, i.e., sclerotized, female genitalia. Most have only six eyes (vs. the eight eyes of typical entelegyne spiders), though spiders in the Filistatidae and and Plectrueridae have eight, while spiders in the Caponiidae have two or four;
  • Superfamily Scytodoidea (skey-toh-DOY-dee-uh) — four families of six-eyed spiders with similar morphological characters: the Drymusidae (false violin or leaf-litter spiders, found mostly in the Caribbean and South America), the Periegopidae (one genus with two species, found in Australia and New Zealand, Scytodidae (spitting spiders), and the Sicariidae (recluse spiders);
  • Family Scytodidae (skey-TOH-dih-dee) — first described in 1864 by the British naturalist John Blackwell (1790-1881), at the grand old age of 74, following Latreille’s 1804 crafting of the generic name, Scytodes.
  • Genus Scytodes (skey-TOH-dees) — first described in 1804 by the French zoologist Pierre André Latreille (1762–1833), at age 42, using the Greek word σκυτος (SKEY-tohs) = skin, tanned hide, to reference the markings on the carapace of the most common spitting spider found worldwide, Scytodes thoracica, which appear similar to finely tanned cowhide, with the hair still on the hide;
  • Species Scytodes thoracica (skey-TOH-dees thoh-RAH-sick-uh) — the specific name thoracica was first described in 1802 by the French zoologist Pierre André Latreille (1762–1833), at age 40; several Greek words figured in the construction of this name: θωραξ (THOR-axe) = a breastplate (perhaps a reference to the extraordinarily convex carapace, which gives the illusion of a formidable guard against predators), θουρος (THOR-ohs) = rushing, impetuous + ακις (AH-kiss) = a point or barb, possibly a reference to the fangs that are used to deliver the fatal coup de grâce bite after the spider’s prey is immobilized by its venom/glue “spit”;

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Additional Bugsinthenews Articles on Spitting Spiders:

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References to Relevant Scientific Literature:

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BugsInTheNews is a VIEWER-PARTICIPANT WEBSITE.  Click on the link for information on what that means.Questions? Corrections? Comments? BUG ME RIGHT NOW! Telephone  Jerry directly at 512-331-1111, or 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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