Latrodectus hesperus

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Latrodectus hesperus
Latrodectus hesperus female
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Theridiidae
Genus: Latrodectus
Species: L. hesperus
Binomial name
Latrodectus hesperus
Chamberlin & Ivie, 1935[1]

Latrodectus hesperus, the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-shaped red mark on the lower abdomen. This "hourglass" mark can be yellow, and on rare occasions, white. The male of the species is around half this length and generally a tan color with lighter striping on the abdomen. The population was previously described as a subspecies of Latrodectus mactans and it is closely related to the northern species Latrodectus variolus. The species, as with others of the genus, build irregular or "messy" webs: Unlike the spiral webs or the tunnel-shaped webs of other spiders, the strands of a Latrodectus web have no apparent organization. Female black widows have potent venom composed of neurotoxins. Fatalities usually only happen with children and the elderly, however medical treatment may be required for others as well. However, the male black widow is harmless to humans. The female's consumption of the male after courtship, a cannibalistic and suicidal behaviour observed in Latrodectus hasseltii (Australia's redback),[2] is rare in this species. Male western widows may breed several times during their relatively short lifespans.[3] Males are known to show preference for mating with well-fed females over starved ones, taking cues from the females' webs.[4]

The ultimate strength and other physical properties of L. hesperus silk were found to be similar to the properties of silk from orb-weaving spiders that had been tested in other studies. The ultimate strength for the three kinds of silk measured in the study was about 1000 MPa. The ultimate strength reported in a previous study for Nephila edulis was 1290 MPa ± 160 MPa[5]

Gallery

  • Female with egg sac

  • Immature female

  • Female with typical red hourglass on abdomen

  • Male, dorsal view (light coloration)

  • Male, ventral view (light coloration)

  • Male, dorsal view (dark coloration)

  • Male, ventral view (dark coloration)

  • Female, front view, with moth and funnel web spider prey

  • Female, side view

  • Female, ventral view

  • Typical female from California

References

Male western black widow: This image shows the enlarged palpal organs (large dark disks) at the tip of the pedipalps and the spider's eight eyes when the image is expanded.
  1. ↑ Chamberlin, R. V. & W. Ivie. 1935. The black widow spider and its varieties in the United States. Bull. Univ. Utah 25(8): 1-29. [15, f. 1, 4, 6-14, 21, 23-33]
  2. ↑ Andrade, Maydianne C. B. (5 January 1996). "Sexual Selection for Male Sacrifice in the Australian Redback Spider". Science 271 (5245): 70–2. Bibcode:1996Sci...271...70A. doi:10.1126/science.271.5245.70. Retrieved 2007-01-15. 
  3. ↑ "Black Widow Spiders". Hastings Reserve. 
  4. ↑ Johnson, J. Chadwick; Trubl, Patricia Trubl; Blackmore, Valerie;Miles, Lindsay (2011). "Male black widows court well-fed females more than starved females: silken cues indicate sexual cannibalism risk". Animal Behaviour 82 (2): 383–390. doi:10.1016/j.anbehav.2011.05.018. 
  5. ↑ Blackledge, et al., Todd. "Quasistatic and continuous dynamic characterization of the mechanical properties of silk from the cobweb of the black widow spider Latrodectus hesperus, table 1". The Company of Biologists. Retrieved 2009-01-23. 
  • Minus, A. 2001. "Latrodectus hesperus" (On-line), Animal Diversity Web. Accessed March 8, 2009
  • Platnick, N. I. 2008. Theridiidae The World Spider Catalog, version 9.0. American Museum of Natural History.

External links

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