Scytodes thoracica (Spitting Spider)

About Scytodes thoracica

Taxonomic Hierarchy

→ Kingdom: Animalia
→ Phylum: Arthropoda
→ Class: Arachnida
→ Order: Araneae
→ Family: Scytodidae
→ Genus: Scytodes
→ Species: Scytodes thoracica

Other Common Names

Spitting Spider, Ornate Spitting Spider

Author

Author of species name: Pierre André Latreille. First year published: 1802, as Aranea thoracica.

Pronunciation

sky-TOH-deez tho-RASS-ih-kuh

Meaning

The genus name Scytodes comes from the Greek adjective for “like leather” (Cameron 2005). The specific epithet, thoracica, is from the latinized Greek for “resembling a breastplate.” Likely chosen because of the carapace markings.

Identifying Traits of Scytodes thoracica

Size

Body length (excluding legs) of adult female ranges from 4-6 mm; adult males range from 3-5 mm.

Female Primary Colors

Male Primary Colors

Eye diagram of Scytodes thoracica

Eyes

Total of only six eyes, arranged in a triad of three pairs (see diagram). This eye arrangement is similar to that of the “recluse spiders” in the genus Loxosceles, however, it is easy to differentiate them based on other obvious physical characteristics. For example, Scytodes thoracica has a dome-shaped carapace and dark spots and stripes on its body.

Legs

The legs of both the male and the female are pale and spindly, without any large or obvious spines, and are banded in dark brown or black. Tarsi (tips of legs) have 3 claws.

Body

Males and females are very similar in general appearance. Both body segments, the cephalothorax and abdomen, are fairly rounded and usually about the same size. The adult male’s palpal organs are so small and slender that they are difficult to see, so telling the gender of these spiders is tough without a magnified view. When viewed from the side, the cephalothorax is low and narrow in the front and then slopes upwards in the back, giving it a dome-like appearance. Housed within that “dome” are the two enlarged lobes of the venom glands which produce the sticky glue and silk the spider uses to subdue its prey. The venom itself is produced in the smaller, frontal portions of the glands and, when expelled, the substances are mixed together. The spider is pale with distinct dark brown or black markings. The shape of the dark pattern on the carapace is reminiscent of a lyre, a type of stringed instrument. There does not seem to be much variation in color or pattern in this species.

Range of Scytodes thoracica

Scytodes thoracica can be found in the following states, provinces and territories across the United States and Canada. Our current understanding of each spider's distribution is drawn from numerous scientific publications and online spider submissions, in order to be as accurate as possible. It is important to remember that spiders do not adhere to the territorial lines decided on by humans, therefore these ranges are subject to change.

Important Range Notes

If you have evidence that Scytodes thoracica has become established in additional states or provinces, we would love to hear from you. It is sometimes difficult to track the movement of synanthropic species such as this one. Also, aside from North America, it is found in Europe, Asia, Australia, and the Pacific Islands (perhaps elsewhere, as well).

United States

Canada

Additional Information

Habitat

In North America, this species is almost exclusively found in and around homes and other buildings. They are mainly nocturnal, so finding them in cellars, closets, and dark corners is commonplace. They can sometimes be found outdoors under rocks or within leaf litter in close proximity to homes, as well.

Web

Though some other species in the genus Scytodes do build space-filling webs, Scytodes thoracica, in particular, does not seem to do so. It is usually found at night, slowly wandering around, or simply not moving at all, and not associated with any webbing. However, they can produce silk like other spiders, and may lay down a little bit of webbing around their daytime retreat. The ability to spit a sticky mixture of silk, venom, and glue onto their prey means they do not really need a web anyways. They hunt “on foot” at night instead.

Season

Adults of this species are usually seen in the summer and fall; mating and egg-laying also occur during those seasons.

Food

The “Spitting Spider” is opportunistic and will capture and eat any insect or spider it is able to subdue with its spray of venom-soaked silk and glue. The spider typically stalks the prey until it can get within 10-15 millimeters of it, and then “spits.” The sticky substance is expelled so forcefully that the fangs and chelicerae (jaws) oscillate and cause the spray to come out in a zigzag pattern. After the “spit” has made contact, it actually shrinks by about 40-60%, which helps to further constrict and immobilize the prey (Suter & Stratton 2009). Once the prey is stuck down and unable to escape, the spider moves in to bite and inject venom. It then backs away momentarily to wait for the toxin to take effect before beginning to feed.

Lifecycle

It can take as many as two or three years for a female Scytodes thoracica to reach maturity, a little less for the males. The availability of prey can greatly influence how long it takes for the spiders to mature; less food means it can take longer. When it comes to mating, there isn’t much preliminary courtship in this species. The male basically just shows up and touches the female with his legs and then climbs over and under her. The female subsequently lays a batch of about 20-35 eggs. Bristowe (1958) mentions that only one brood (i.e. egg sac) is created per year. Females carry the egg sac beneath their body, held in their pedipalps (not chelicerae) as well as attached to a tether of silk coming from the spinnerets. They slowly tip-toe around to prevent dragging the eggs across the ground. Spitting spiders have reduced spigots on their spinnerets and so do not construct thick egg sacs as do many other types of spider; instead they simply bind the eggs together with a few strands of silk. Scytodes thoracica mothers have been witnessed eating their own eggs after being disturbed too much while carrying them (Dabelow 1958), a practice that seems to happen in various other kinds of spider, as well. The spiderlings (baby spiders) emerge from the egg shells (chorions) about 2-3 weeks later and will remain huddled together near the mother, who stands guard, until after they have completed their first molt. They then disperse and go their own separate ways.

Remarks

In addition to Scytodes thoracica, there are at least eight other described species of “Spitting Spider” that have been collected in the United States; some may be endemic to the southern states, others may be synanthropic and were introduced from Central and South America via commerce. In our research, we found collection records for the following species: S. atlacoyaS. dorothea, S. fusca, S. globula, S. longipes, S. lugubris, S. univittata, and S. zapatana. There are also various undescribed or unidentified species of Scytodes that have been collected in the United States, as well. For Canada, as of the year 2010, only two species have been formally collected there: S. fusca in Quebec, and S. thoracica in Ontario (Paquin et al. 2010).

Pictures of Scytodes thoracica

General

Female Spiders

Male Spiders

Filtering options are grayed out when we do not have pictures for the given perspective. If you are a spider photographer, you can submit pictures of spiders to help fill any voids in our ever expanding library.
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Dorsal
  • City/Region: Windsor
  • Country: United Kingdom
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Eyes
  • City/Region: Rome, Lazio
  • Country: Italy
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Dorsal
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Dorsal, Gravid, Lateral
  • City/Region: Cushing Square, Belmont
  • State: Massachusetts
  • Country: United States
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Egg Sacs, Lateral
  • City/Region: Rome, Lazio
  • Country: Italy
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Eyes
  • City/Region: Hesse
  • Country: Germany
  • Scytodes thoracica
  • Sex: MaleMale
  • Maturity: Immature
  • Attributes: Lateral
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Eyes
  • City/Region: Hesse
  • Country: Germany
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Lateral
  • City/Region: Hesse
  • Country: Germany
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Eyes
  • State: Washington, D.C.
  • Country: United States
  • Scytodes thoracica
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Ventral
  • State: Washington, D.C.
  • Country: United States
  • Scytodes thoracica
  • Sex: MaleMale
  • Maturity: Adult
  • Attributes: Lateral

References and Further Reading

Various Research Papers

Scientific Diagrams and Keys for Identification

References for the Casual Reader

Species guide last updated: May 29, 2016

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