Animal Diversity Web

Ge­o­graphic Range

Mem­bers of the genus Scy­todes are pre­dom­i­nately trop­i­cal or sub­trop­i­cal spi­ders. How­ever, spit­ting spi­ders are found scat­tered across neartic, paleartic, and neotrop­i­cal re­gions. This species is com­monly found in the east­ern United States, as well as in Britain, Swe­den and other Eu­ro­pean coun­tries. Spec­i­mens have also been found in Japan and Ar­gentina. It is un­clear which pop­u­la­tions are na­tive and which are in­tro­duced in these re­gions. The pres­ence of this species in more north­ern cli­mates is at­trib­uted to the avail­abil­ity of warm houses and build­ings, to which these spi­ders have adapted. ("The Spi­der Book", 1912; Emer­ton, 1902; Kas­ton, 1972; "Scy­todes tho­racica (Spit­ting spi­der)", 2011; Ubick, et al., 2005)

• Biogeographic Regions
• nearctic
• palearctic
• neotropical
• oceanic islands

Habi­tat

Spit­ting spi­ders are found in tem­per­ate forests. When as­so­ci­ated with hu­mans, they are most com­monly found in dark cor­ners, cel­lars, cup­boards, and clos­ets of houses and other build­ings. ("Spit­ting spi­der Scy­todes tho­racica", 2012)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• forest

• Other Habitat Features
• urban
• suburban
• agricultural

• Average elevation

  Sea Level m

  ft

Phys­i­cal De­scrip­tion

This species has long, thin, legs, and are glabrous (hair­less), with the ex­cep­tion of short sen­sory setae scat­tered over the body. These spi­ders are also eas­ily iden­ti­fied by their over­sized cephalotho­rax (pro­soma), which slopes up­ward to­wards their pos­te­rior ends. Their ab­domens (which are roughly the same cir­cu­lar shape as the cephalotho­rax) slope down­wards and are only slightly smaller than the cephalotho­rax. Like all spi­ders, these two body tag­mata (seg­ments) are sep­a­rated by a thin pedi­cel (waist-like con­nec­tor). (Emer­ton, 1902; Goethals, 1997; Kas­ton, 1972; Larsen, 2005; Robin­son, 2005)

Large, well-de­vel­oped poi­son glands are lo­cated in the cephalotho­rax. These glands are di­vided into two parts: a smaller, an­te­rior com­part­ment which stores venom and a larger, pos­te­rior com­part­ment which con­tains a mu­cilagi­nous sub­stance. These spi­ders pro­duce a gummy sub­stance which is a mix of the two sub­stances and is ex­creted by their fused che­licerae, which can not be moved sep­a­rately. Scy­todes are ecribel­late, lack­ing the silk-spin­ning organ (cribel­lum) of some other spi­ders. They have a sin­gle tra­cheal spir­a­cle. (Emer­ton, 1902; Goethals, 1997; Kas­ton, 1972; Robin­son, 2005)

Spit­ting spi­ders have pale yel­low bod­ies with black speck­led mark­ings on the cephalotho­rax, which slightly re­sem­ble a lyre. Their legs, which slowly taper in size as they ex­tend from their bod­ies, are long with black bands. The most an­te­rior por­tion of the head, below the eyes, pro­jects for­wards, past the mandibles. This species ex­hibits sex­ual di­mor­phism, with males typ­i­cally rang­ing from 3.5-4 mm in length and fe­males rang­ing from 4-5.5 mm. (Emer­ton, 1902; Gertsch, 1949; Goethals, 1997; Kas­ton, 1972; Robin­son, 2005)

• Other Physical Features
• ectothermic
• bilateral symmetry
• venomous

• Sexual Dimorphism
• female larger

• Range length

  3.5 to 5.5 mm

  0.14 to 0.22 in

De­vel­op­ment

All spi­ders re­pro­duce sex­u­ally, and sex is de­ter­mined by meio­sis. Fol­low­ing cop­u­la­tion and egg fer­til­iza­tion, fe­males lay eggs in a co­coon car­ried under their bod­ies for 2-3 weeks until eggs hatch. Spi­der­lings re­main with their moth­ers until their first molts and then dis­perse to live soli­tary lives, reach­ing adult­hood after 5-7 molts. It can take 2-3 years for fe­males to reach ma­tu­rity. ("Spit­ting spi­der Scy­todes tho­racica", 2012; Gertsch, 1949; Guar­isco, 1991; Koh, et al., 2009; Larsen, 2005)

Re­pro­duc­tion

Spit­ting spi­ders are soli­tary, in­ter­act­ing only dur­ing mat­ing. These spi­ders are ag­gres­sive hunters, so males must ap­proach fe­males cau­tiously or else be mis­taken for prey. Both sexes pro­duce pheromones, which are de­tected through con­tact with chemosen­sory hairs cov­er­ing the pedi­palps and first pair of legs; fe­male mate choice is based on male pheromone pro­duc­tion. Lo­ca­tion of mates is not based on vi­sual cues and mat­ing usu­ally oc­curs fol­low­ing an ac­ci­den­tal meet­ing of a male and fe­male. Upon meet­ing a fe­male, male spit­ting spi­ders fill their pal­pal or­gans (ac­ces­sory re­pro­duc­tive parts on the ends of each pedi­palp) with sperm. They do this by draw­ing a sperm web across their gen­i­tal open­ings to ac­cu­mu­late sperm droplets, using their third pair of legs. In Scy­todes, the sperm web is a sin­gle thread which typ­i­cally takes a tri­an­gu­lar shape. From there, sperm droplets are drawn into the pal­pal organ (bulb). Males ap­proach fe­males an­te­ri­orly; fe­males raise their cephalotho­raxes to allow males to in­sert both pal­pal or­gans into their gen­i­tal open­ing. Sperm is then de­posited and stored in fe­males' sem­i­nal re­cep­ta­cles. After mat­ing, the pair sep­a­rates im­me­di­ately. Males and fe­males have mul­ti­ple part­ners through­out their life­times. ("Spit­ting spi­der Scy­todes tho­racica", 2012; Foelix, 1982; Koh, et al., 2009; Se­beok, 1977)

• Mating System
• polygynandrous (promiscuous)

Spit­ting spi­ders are dioe­cious and fe­males re­quire 2-3 years to reach ma­tu­rity. Most mat­ing oc­curs in the warmer months (es­pe­cially Au­gust) but these spi­ders can ex­pand their breed­ing sea­sons when liv­ing in warm areas, such as within homes. Sperm can be stored by fe­males for months until eggs are laid. Com­pared to most spi­ders, spit­ting spi­ders lay rel­a­tively few eggs (20-35 eggs per co­coon) and 2-3 co­coons are typ­i­cally pro­duced by a fe­male each year. This species dis­plays ma­ter­nal care both be­fore (fe­males carry egg co­coons) and after hatch­ing, with newly hatched ju­ve­niles re­main­ing with their mother until their first molts. Speed of growth and, there­fore, rate of molt­ing, is closely re­lated to avail­abil­ity of prey and so the time that ju­ve­niles re­main with their mother, as well as the age at which males reach ma­tu­rity, is widely vari­able. These spi­ders can mate mul­ti­ple times and usu­ally die of hunger, ex­haus­tion, or pre­da­tion. (Koh, et al., 2009; Ramel, 2011; Suter and Strat­ton, 2011)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous
• sperm-storing
• delayed fertilization

• Breeding interval

  This species breeds 2-3 times a year.

• Breeding season

  These spiders breed during warmer summer months.

• Range number of offspring

  20 to 35

• Average number of offspring

  28

• Average age at sexual or reproductive maturity (female)

  2-3 years

Fe­male spit­ting spi­ders ex­hibit parental care. They do not make nests or sus­pend co­coons in webs or other struc­tures, but in­stead lay eggs in a co­coon that they carry ei­ther under their bod­ies or in their che­licerae. Fe­males are more vul­ner­a­ble to pre­da­tion dur­ing this egg-car­ry­ing pe­riod, as they are un­able to feed or de­fend them­selves by spit­ting. Eggs typ­i­cally hatch 2-3 weeks after being laid and nymphs (ju­ve­niles) re­main with their moth­ers until their first molts. On oc­ca­sion, fe­males con­sume egg sacs that have re­sulted from mat­ing with non-pre­ferred males or con­tain de­fec­tive eggs. Males dis­play no parental in­vest­ment after mat­ing. (Koh, et al., 2009; Larsen, 2005)

• Parental Investment
• female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • protecting
    • female
• pre-independence
  • protecting
    • female

Lifes­pan/Longevity

Spit­ting spi­ders have a rel­a­tively long life span as they do not die fol­low­ing mat­ing; males live 1.5-2 years and fe­males live 2-4 years. Fe­males may be preyed upon dur­ing their egg-car­ry­ing pe­ri­ods, while males often die of hunger and ex­haus­tion while search­ing for and court­ing fe­males. (Guar­isco, 1991; Larsen, 2005; Ramel, 2011)

• Range lifespan
  Status: wild

  1.5 to 4 years

• Average lifespan
  Status: wild

  2.5 years

Be­hav­ior

Spit­ting spi­ders are pri­mar­ily noc­tur­nal. They are wan­der­ing and soli­tary spi­ders that ac­tively hunt their prey and, due to their long, thin legs, are slow mov­ing. They have ex­tremely poor eye­sight and there­fore walk around with their front legs, which are cov­ered with sen­sory setae, held up in order to sense their en­vi­ron­ments. ("Spit­ting Spi­der", 2004; Suter and Strat­ton, 2005)

When these spi­ders come into con­tact with prey, their at­tacks usu­ally pro­ceed in the fol­low­ing order: tap­ping of the front legs, spit­ting, bit­ing, wrap­ping, and then feed­ing. When a spi­der con­tacts a prey item, it ori­ents it­self to­wards the prey and slowly taps its front legs until the prey is cen­tered be­tween them. It then spits a string of a gluey, ven­omous sub­stance at the prey, cov­er­ing it in 5-17 par­al­lel, over­lap­ping bands. The ma­te­r­ial can travel at a rate of up to 28 m/s and the pat­tern of the bands is pro­duced as the spi­der lifts its che­licerae and os­cil­lates its fangs dur­ing ex­pul­sion. The spi­der then quickly ap­proaches its prey and uses its first and sec­ond pairs of legs to fur­ther en­tan­gle the prey in the dry­ing glue, silk and venom. The ven­omous glue par­a­lyzes the prey and, once it is dry, the spi­der bites its vic­tim, in­ject­ing venom to liquify its tis­sues. It then grooms its first two sets of legs, clean­ing any re­main­ing glue, be­fore draw­ing the prey into its che­licerae using its pedi­palps. The spi­der holds the prey with its third legs and wraps it in silk pro­duced by spin­nerets. It then con­sumes its prey by suck­ing up the dis­solved tis­sues. These spi­ders also use their spit­ting "web" as a de­fen­sive mea­sure against other spi­ders or threats. ("Spit­ting Spi­der", 2004; Suter and Strat­ton, 2005; Suter and Strat­ton, 2011)

• Key Behaviors
• terricolous
• nocturnal
• motile
• daily torpor
• solitary

• Range territory size

  1 to 35 m^2

Home Range

Spit­ting spi­ders will typ­i­cally wan­der within a ter­ri­tory 30-35 m in size. ("Spit­ting Spi­der", 2004)

Com­mu­ni­ca­tion and Per­cep­tion

Al­though they can see, these spi­ders do not rely on vi­sion for mate or prey recog­ni­tion due to their poor eye­sight. How­ever, like most spi­ders, they use chem­i­cal sig­nals to de­tect and re­spond to preda­tors, prey, and mates. Spit­ting spi­ders use their raised front legs to de­tect prey and their en­vi­ron­ment using tri­choboth­ria (sen­sory hairs) on the metatarsi (sec­ond to last seg­ment of the leg). These sen­sory hairs also con­tain chemore­cep­tors, which are sen­si­tive to pheromones. Scy­todes are also known to em­ploy both acoustic and vi­bra­tional com­mu­ni­ca­tion by tap­ping on the ground with their first pair of legs. (Koh, et al., 2009; Se­beok, 1977)

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Other Communication Modes
• pheromones
• vibrations

• Perception Channels
• visual
• tactile
• acoustic
• vibrations
• chemical

Food Habits

Scy­todes are ac­tive noc­tur­nal wan­der­ers, not web-spin­ners. They are in­sec­ti­vores and when liv­ing in­doors, they mostly eat other in­sects and arthro­pods, such as moths (Order Lep­i­doptera), Flies (Order Diptera), other spi­ders (Order Araneae), and house­hold bugs (Order Het­eroptera). When liv­ing out­doors, they eat sim­i­lar food items and, in the Philip­pines, are known to eat in­sects such as green scale (Coc­cus viridis), black cit­rus aphids (Tox­optera au­ran­tii), cit­rus mealy­bugs (Planococ­cus citri), Philip­pine katy­dids (Phaneroptera fur­cifera) and lime swal­low­tails (Pa­pilio de­moleus). In Britain, mos­qui­tos (Fam­ily Culi­ci­dae) are often eaten. Many of their prey items are sig­nif­i­cantly larger than these spi­ders. Fe­males may also oc­ca­sion­ally con­sume their own egg sacs. ("Spi­der Fauna in Philip­pine cit­rus and their note as preda­tor in the con­trol of in­sect", 1989; "Spit­ting Spi­der", 2004; Gertsch, 1949; Gilbert and Rayor, 1985; Larsen, 2005; Med­lock and Snow, 2008)

• Primary Diet
• carnivore
  • eats eggs
  • insectivore

• Animal Foods
• insects

Pre­da­tion

Since spit­ting spi­ders are slow mov­ing, they use their spit­ting ap­pa­ra­tus against preda­tors, rather than at­tempt­ing to flee. In­doors, the ma­jor­ity of its preda­tors are house­hold arthro­pods such as other spi­ders and cen­tipedes, and may in­clude mam­mals such as do­mes­tic cats. In the wild, spit­ting spi­ders may be prey for bats, toads, birds, and shrews. Ad­di­tion­ally, hu­mans play a major fac­tor in con­trol­ling pop­u­la­tions of this species through pest con­trol. (Atkin­son, 2002; Bris­towe, 1941; Suter and Strat­ton, 2005)

• Known Predators

  • Common house spider (Parasteatoda tepidariorum)
  • Wolf Spiders (Hogna carolinensis)
  • House centipede (Scutigera coleoptrata)
  • American toad (Anaxyrus americanus)
  • Little brown bat (Myotis lucifugus)
  • House Sparrow (Passer domesticus)
  • Domestic cat (Felis catus)
  • Shrew (Soricidae sp.)

Ecosys­tem Roles

When as­so­ci­ated with hu­mans, this spi­der's largest ecosys­tem role is in the con­trol of in­sect pop­u­la­tions, mostly of house­hold pest species. They also serve as food for house cen­tipedes (Scutig­era coleop­trata) and other arthro­pod car­ni­vores found in homes. In the wild, they may be preyed upon by a num­ber of other species. (Gertsch, 1949; Kas­ton, 1948)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

This species con­tributes to the dis­posal of house­hold pest in­sects and could po­ten­tially save home­own­ers money on in­vest­ing in other meth­ods of pest con­trol. (Bris­towe, 1941; Gertsch, 1949)

• Positive Impacts
• controls pest population

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Though this species plays a role in con­trol­ling in­sect pop­u­la­tions, it may also be con­sid­ered a house­hold pest. Many home-own­ers in­vest in pest-con­trol in order to ex­ter­mi­nate these spi­ders. Ad­di­tion­ally, this spi­der is ven­omous, al­though its che­licerae, or fangs, are too small to pierce human flesh. (Bris­towe, 1941; Gertsch, 1949)

• Negative Impacts
• household pest

Con­ser­va­tion Sta­tus

This species is a com­mon house spi­der of the United States. It is less com­monly found in Eu­rope, Ar­gentina, and Japan, but its con­ser­va­tion sta­tus is not a con­cern. ("Spit­ting Spi­der", 2004)

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Jacque­line Brand (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Je­remy Wright (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

1912. The Spi­der Book. Gar­den City, new York: Gar­den City, new York.

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