A Male Trapdoor spider in San Antonio, Texas

— This article by Jerry Cates and Joy R., first published on 21 March 2010, was last revised on 10 January 2013. © Bugsinthenews Vol. 11:03(19).


Mygalomorph, Joy R 031910, laterodorsal body

Mygalomorph, Joy R 031910, laterodorsal body

The spider depicted on this page was photographed by Joy R., of San Antonio, Texas.

Joy wrote:

Jerry, this is the second of these spiders I have found in my living room.

My first instinct is to whack it with a shoe until it stops moving but I know how you bug people feel about that.

I just want to know if it’s dangerous other than the fact that I feel like I’m going to have a seizure when I see it!

Also, if I let it outside, far from the house, will it likely return?

Kindly, Joy R.

We see a lot of trapdoor spiders marching around in Texas after a cool rain. Many are dark black (others are chestnut, reddish, or tan), with shiny, almost plastic-looking heads (some have heads that are textured with a pebble-like surface), all have stout legs, and all have large, forward-reaching fangs that stretch out in front of their faces. Almost without exception they are males who are looking for females.

In the following narrative, replete with photos, we will refer to anatomical characters that bear on its identity, as described by a number of authorities, including the key provided in Ubick 2005, p. 25-37. Major changes to the taxonomy of the Mygalomorph spiders have recently taken place that must be taken into account before we can arrive at a conclusion regarding this spider’s taxonomical identity. In fact, because we do not have definitive images of this specimen’s genitalia, and no effort could be made to find and examine its burrows, arriving at a firm conclusion in this regard is practically impossible. Regardless, much can still be said about this spider.

Mygalomorph, Joy R 031910, pars cephalica and palpae

Mygalomorph, Joy R 031910, pars cephalica and palpae

Mygalomorph, Joy R 021910, pars cephalica and palpae 2

Mygalomorph, Joy R 021910, pars cephalica and palpae 2

In these photos, subtle anatomical features of the spider have been made more visible using image enhancement software. The original images Joy sent in were of an almost totally black spider, but the enhanced images show important details.

Notice, for example, the palps in front of the spider’s face. These structures look like diminutive legs, with swollen, elongated tips. Male mygalomorphs have enlarged palpal tarsi, which are actually insemination devices used by the spider to transfer semen into the female’s seminal vesicles during mating. Females have palps with ordinary tarsi (i.e., that are not enlarged), so that the palps appear as ordinary, but diminutive, legs.
Trapdoor spiders are a sign of a healthy lawn. These spiders will bite if picked up, especially if handled roughly. But, even though the bite can be quite painful, their venom is not considered dangerous to humans or our large pets.
My reply to Joy:


These guys (they are guys, for a fact) are pretty gnarly and big, aren’t they? And black, dark black.

They are harmless, essentially, though if you pick one up and play with it, and get rough enough to make it think you are a threat, it will bite and the bite will be painful–but of no medical consequence.

These are trapdoor spiders in the Megalomorphae. Probably in the family Cyrtaucheniidae. I have posted a photo of a very similar specimen on another page along with some text to explain the habits of this spider. Basically the males leave their nests in the soil, after a cool rain, to look for females. They then sometimes end up in our homes.
Hope this helps you sleep better.

Tell me where you are (city and state will do) and describe how it behaved. And, no, if you let it outside, far from the house, it won’t likely return. It isn’t looking for you, but for a female of its species. Especially if you will let it out in a place where that search will be successful.


She wrote back to say she lived in San Antonio, Texas.  Another posting relating to the trapdoor spiders can be reached by CLICKING HERE.


Joy wrote back again on March 23, 2010:


I just had a chance to read the addition to the section on this spider including my pictures.

I have to say, it almost makes me not hate spiders. 🙂

Honestly, I do appreciate what spiders do in my yard and in nature in general but I typically don’t feel that appreciation for them in my home.

Part of my fear stems from an incident six or seven years ago in Washington State with a spider simiar in size to the one we’ve been talking about. I actually woke in the night to find it on my cheek. I saw this as a violation of our relationship and have had a very hard time when I’ve seen them in my home ever since. Especially when they are big, black, and hairy.

The little ones I don’t mind so much but the ones that can stare back at you disturb me.

It was so good to learn about what’s in my home. If I see any more in the future, I’ll take photos and send them, although I have to say that I hope it isn’t soon. 🙂




  • 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 (1762 – 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 (SAIR-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 (1769 – 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 – 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 Mygalomorphe (my-GAL-oh-MOHR-fee) — spiders with paraxial chelicerae and two pairs of book lungs, as in the more primitive Mesothelae, but without the latter’s tergite plates and most of the latter’s abdominal ganglia, and having their spinnerets positioned at the abdomen’s hindmost portion rather than mid-ventrally as in the Mesothelae; presently comprised of fifteen families:
    • Atypidae (Thorell 1870) — 3 genera, 49 species (Platnick WSCv13.5); commonly known as purseweb spiders; 8-27 mm, yellow-brown to dark purple-black in color; the legs of male specimens of Sphodros rufipes (Latrielle 1829) and S. fitchi (Gertsch & Platnick 1980) are bright orange-red;
    • Antrodiaetidae (Gertsch 1940) — 2 genera, 33 species (Platnick WSCv13.5); commonly known as foldingdoor, collardoor, or turret spiders (Antrodiaetus), and trapdoor spiders (Aliatypus); 6-26 mm, tan to chestnut brown, with one or more tergites on the anterodorsal abdomen; live in burrows with a flexible collar, a rigid turret, or a trapdoor at the mouth;
    • Mecicobothriidae (Holmberg 1882) — 4 genera, 9 species (Platnick WSCv13.5); no common name; mygalomorphs with two tergites on their anterodorsal abdomen (these sclerotized patches may be fused); build sheet webs with silk tubes from sheet to ground that lead into hiding places under terrestrial objects;
    • Hexathelidae (Simon 1892) — 12 genera, 112 species (Platnick WSCv13.5);
    • Dipluridae (Simon 1889) — 24 genera, 179 species (Platnick WSCv13.5); commonly known as mygalomorph funnelweb spiders; 3.5-17 mm, pale tan to purple-brown in color; thoracic furrow in the form of a short longitudinal groove or a shallow pit or rounded depression;
    • Cyrtaucheniidae (Simon 1889) — 10 genera, 102 species (Platnick WSCv13.5);
    • Ctenizidae (Thorell 1887) — 9 genera, 128 species (Platnick WSCv13.5); no common name; 10-30 mm or more in length, tan, dark chestnut brown, and black in color; the females lack scopulae, but are equipped with a number of robust lateral digging spines on their pedipalps, as well as on the tarsus, metatarsus, and tibia of legs I and II; carapace generally glabrous, with few distinct spines; thoracic furrow is transverse, typically very deep and procurved; burrows are covered with a thick cork-type trapdoor for all genera, except Cyclosmia Ausserer 1871, which have wafer-type trapdoors;
    • Euctenizidae (Raven 1985) — 7 genera, 33 species (Platnick WSCv13.5);
    • Idiopidae (Simon 1889) — 22 genera, 314 species (Platnick WSCv13.5);
    • Actinopodidae (Simon 1892) — 3 genera, 40 species (Platnick WSCv13.5);
    • Migidae (Simon 1889) — 10 genera, 91 species (Platnick WSCv13.5);
    • Nemesiidae (Simon 1889) — 43 genera, 364 species (Platnick WSCv13.5); 16-30 mm, golden brown to dark gray, generally concolorous but sometimes with an indistinct chevron pattern on the dorsal abdomen;
    • Microstigmatidae (Roewer 1942) — 7 genera, 16 species (Platnick WSCv13.5);
    • Barychelidae (Simon 1889) — 44 genera, 307 species (Platnick WSCv13.5);
    • Theraphosidae (Thorell 1869) — 124 genera, 946 species (Platnick WSCv13.5);
    • Paratropididae (Simon 1889) — 4 genera, 8 species (Platnick WSCv13.5);
  • Family not presently determined;
  • Genus not presently determined;
  • Species not presently determined;




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