Cheiracanthium inclusum

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Cheiracanthium inclusum
Inside a house during the winter
Scientific classification edit
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Cheiracanthiidae
Genus: Cheiracanthium
C. inclusum
Binomial name
Cheiracanthium inclusum
(Hentz, 1847)

Clubiona inclusa
Clubiona subflava
Cheiracanthium lanipes
Cheiracanthium edentulum
Clubiona melanostoma
Cheiracanthium keyserlingii
Cheiracanthium subflavum
Cheiracanthium ragazzii
Cheiracanthium viride
Cheiracanthium ferum
Cheiracanthium debile
Eutichurus frontalis
Cheiracanthium popayanse
Cheiracanthium gracilipes
Cheiracanthium africanum
Chiracanthops mandibularis
Matidia haplogyna
Radulphius seminermis
Cheiracanthium leitaoi
Cheiracanthium melloi
Radulphius brachyapophysis
Cheiracanthium nigropalpatum

Cheiracanthium inclusum, alternately known as the black-footed yellow sac spider or the American yellow sac spider (in order to distinguish it from its European cousin C. punctorium), was formerly classified as a true sac spider (of the family Clubionidae), and then placed in the family Miturgidae, but now belongs to family Cheiracanthiidae.[1] It is a rather small pale yellow species that is indigenous to the Americas and can be found living in the foliage of forests and gardens but also can inhabit human homes.[2] Despite common beliefs of necrosis, Cheiracanthium bites cause only localized swelling.[3] C. inclusum is closely related to Cheiracanthium mildei, an introduced species native to Europe which is similar in appearance and natural history and can also be found in North American homes.[4]


Like all spiders, C. inclusum has two body segments: a cephalothorax (fused head and thorax) and an abdomen. In females, the body measures between 5 and 9 mm and in males, 4 to 8 mm. The leg span however can be up to 1 inch (2.5 cm) with the front pair of legs being longer than the other 3 pairs.[5] Males tend to have a narrower body and a larger leg span than females.[2] C. inclusum gets its two common names (yellow sac and black-footed spider) from its appearance. It is a pale yellow-beige colour with dark brown markings on its palps, chelicerae (jaws) and on the ends of its tarsi (feet). There is also often an orange-brown stripe running down the top-centre of its abdomen.[4] C. inclusum has 8 similarly sized eyes, distributed in 2 parallel horizontal rows. However, ocular input is of minor import, due to the absence of light during the spider's nocturnal activities. The spider relies more on its palps, sensory structures just behind the chelicerae, on the cephalothorax, to sense its environment.[6]

Natural history[edit]


C. inclusum are native to the New World (North, Central, and South America; and West Indies).[7] This species has also been introduced to Africa and Réunion.[8] They are most often found in trees and shrubs, but may also find shelter in houses and other human-made structures.[2]

Life cycle[edit]

Females of C. inclusum mate only once, and produce their first egg mass about 14 days after mating. Two sets of eggs are usually produced, but this can range anywhere from 1 to 5. Egg masses generally contain 17 to 85 eggs, although as many as 112 eggs have been reported in a single egg mass.[2] Egg laying generally occurs during the months of June and July; during this period, females lay their eggs in small (2 cm) silk tubes and enclose themselves with the eggs, protecting them from predators. Females stay with the eggs and juvenile spiders for about 17 days – until their first complete molt. Females which produce additional egg masses construct a second egg sac about two weeks after the juvenile spiders disperse. Males tend to become sexually mature earlier (119 days on average) than females (134 days on average), but time to maturity can range from 65 to 273 days, depending on a number of factors, such as temperature, humidity and photoperiod. C. inclusum spiders normally over-winter as adults or sub-adults.[7]


Being nocturnal, C. inclusum feed and mate at night. C. inclusum do not make webs to catch prey; instead, they are active predators, feeding on a variety of arthropods such as insects and other spiders. Prey detection may involve detection of mechanical vibrations of the substrate, and vision seems to play an insignificant role.[9] During the day, they retreat in small silk nests similar to those used for reproduction. A new nest, which may be completely closed, open on one side, or open on both sides, is built every day in under 10 minutes.[citation needed]

C. inclusum are known to disperse easily between trees and shrubs. They do this by excreting a long silk thread that gets carried by the wind and sticks to a nearby structure, forming a scaffold between two structures. Alternatively, the spider may stay attached to the thread and balloon through the air.[7] These spiders are infamous for their vertical traveling attached to a silk string, which they use in order to both catch airborne prey, and keep out of reach of other predators, such as larger spiders, centipedes or ants.

Human impact[edit]

C. inclusum spiders are venomous and capable of biting humans. A bite begins with moderate pain (in contrast to a brown recluse spider's painless bite) followed by itching.[citation needed] Symptoms usually resolve within 7–10 days. However, the spider rarely bites (with females biting more often than wandering males), and the venom rarely produces more than local symptoms.[3][10]

In March 2011, Mazda initiated a recall of 65,000 Mazda6 automobiles after webs of this species were found to have clogged fuel system ventilation tubes.[11] It is unclear why the spiders were drawn to build webs inside this particular vehicle, but the problem appeared to be widespread, though rare, across the United States.[12] Mazda initiated a recall of an additional 42,000 Mazda6 automobiles for the same reason in April 2014.[13]


  1. ^ "Taxon details Cheiracanthium inclusum (Hentz, 1847)", World Spider Catalog, Natural History Museum Bern, retrieved October 7, 2015 CS1 maint: discouraged parameter (link)
  2. ^ a b c d Edwards, Robert J. (1958). "The spider subfamily Clubioninae of the United States, Canada and Alaska (Araneae: Clubionidae)". Bulletin of the Museum of Comparative Zoology. 118 (6): 365–436. OCLC 248254142.
  3. ^ a b Vetter, Richard S.; Isbister, Geoffrey K.; Bush, Sean P.; Boutin, Lisa J. (2006). "Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: where is the necrosis?". The American Journal of Tropical Medicine and Hygiene. 74 (6): 1043–8. doi:10.4269/ajtmh.2006.74.1043. PMID 16760517.
  4. ^ a b "Miturgidae – Prowling Spiders". Retrieved February 20, 2009. CS1 maint: discouraged parameter (link)
  5. ^ "Ohio State University Extension Fact Sheet – Sac Spiders". Archived from the original on July 14, 2012. Retrieved February 20, 2009. CS1 maint: discouraged parameter (link)
  6. ^ "Glossary of Spider Terms". Retrieved February 20, 2009. CS1 maint: discouraged parameter (link)
  7. ^ a b c Peck, William B.; Whitcomb, Willard Hall (1970). "Studies on the biology of a spider, Chiracanthium inclusum (Hentz)". Bulletin. Agricultural Experiment Station. 753: 1–76. OCLC 4505537.
  8. ^ Rochat, J.; Gasnier, S. (2006). "Evaluation de l'impact des traitements de demoustication sur la faune d'arthropodes non-cible" (PDF) (in French). Insectarium de La Réunion. Archived from the original (PDF) on July 20, 2011. CS1 maint: discouraged parameter (link)[page needed]
  9. ^ Amalin, Divina M.; Reiskind, Jonathan; Peña, Jorge E.; McSorley, Robert (2001). "Predatory Behavior of Three Species of Sac Spiders Attacking Citrus Leafminer". Journal of Arachnology. 29 (1): 72–81. doi:10.1636/0161-8202(2001)029[0072:PBOTSO]2.0.CO;2. JSTOR 3706123.
  10. ^ Diaz, James H. (2004). "The global epidemiology, syndromic classification, management, and prevention of spider bites". The American Journal of Tropical Medicine and Hygiene. 71 (2): 239–50. doi:10.4269/ajtmh.2004.71.2.0700239. PMID 15306718.
  11. ^ "National Highway Traffic Safety Administration Campaign ID #11V134000 – Mazda recall notice".[permanent dead link]
  12. ^ Hsu, Tiffany (March 3, 2011). "Mazda recalls 65,000 cars for spider problem". Los Angeles Times.
  13. ^ "For Real? Mazda's latest recall due to a spider, man". April 5, 2014.

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