This species has eight simple eyes aligned in two rows of four, consisting of secondary and primary eyes. Secondary eyes are light sensitive and adept at tracking movement. Primary eyes are the only set of movable eyes and are used to view objects within a close proximity. Spiders can dectect touch, vibrations, and smells through various setae connected to their nervous system.
Communication Channels: visual ; tactile
Other Communication Modes: vibrations
Perception Channels: visual ; tactile ; vibrations ; chemical
This species currently has no special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Mating season is assumed to be during the summer months, due to increasing populations observed during this time. After mating, females produce egg sacs within about 14 days, guarding the eggs and immature spiders for about 17 days, repeating this process multiple times during breeding season. Throughout develpment, yellow sac spiders undergo molting in order to grow, usually from within the protection of their silk sacs. These spiders overwinter as juveniles in the safety of these silk sacs, molting and achieving adulthood in late spring and emerging from the egg sac.
Yellow sac spiders are regularly found in close proximity to humans, within homes or during outdoor activities. They possess a cytotoxic venom, which can have necrotizing effects. Although necrotic legions are rare, these spiders may be quite aggressive, particularly females defending eggs, and can administer painful bites that may require medical attention.
Negative Impacts: injures humans (bites or stings, venomous ); household pest
These spiders are vital predators of agricultural pests; their presences results in higher crop yields and greater financial gain.
Positive Impacts: controls pest population
Yellow sac spiders are secondary consumers and are valuable anti-pest predators in agricultural ecosystems, particularly in vineyards, apple orchards and cotton fields.
Species Used as Host:
Mutualist Species:
Commensal/Parasitic Species:
Yellow sac spiders prey upon anthropods such as leafhoppers (Erythroneura variabilis), fleahoppers (Pseudomatoscelis seriatus), fruit flies (Drosophila sp)and cotton plant bugs (Creontiades signatus) as well as eggs of lepidopterans such as Helicoverpa zea and Plutella xylostella. They have also been known to prey on other spiders including Anyphaena pacifica and Theridion melanurum. Aside from their predatory diet, these spiders consume nectar as they forage. Nectar consumption elevates fitness through increased survival, growth, and fecundity, especially during periods of prey scarcity. Incorporation of nectar into the diet can also accelerate sexual maturity and enhance offspring volume.
Animal Foods: insects; terrestrial non-insect arthropods
Plant Foods: nectar
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)
Yellow sac spiders (sometimes known as agrarian sac spiders) are found throughout North and South America, including Mexico and the West Indies, United States, and southern Canada. There are also accounts of yellow sac spiders being found in Africa, which indicates that it may be an introduced species to that continent.
Biogeographic Regions: nearctic (Introduced ); ethiopian (Introduced )
Yellow sac spiders form silk tube-like sacs under ground debris and within man-made structures, hiding within these tubes during the day. Alternatively, the spiders may roll themselves up in leaves or other debris during daytime hours or in other tight places providing protection. This species occupies a wide variety of habitats, including trees, forest floors, fruit orchards and other agricultural areas, and shrubs surrounding open fields (most of the biomes within the United States).
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest
Other Habitat Features: urban ; suburban ; agricultural
There is no currently available information regarding the lifespan of yellow sac spiders.
Yellow sac spiders are typically cream to light yellow in color, sometimes with an orange-brown stripe running lengthwise across the abdomen. While individuals are uniform in base color, their chelicerae, tarsi, and pedipalps are dark brown. The body color is partially determined by their diet; individuals known to feed on house flies are noticeably more gray in color, while those who feed on red-eyed fruit flies take on a reddish tinge, and so forth. Females are slightly larger than males, 5-10 mm and 4-8 mm, respectively. Although females' bodies are slightly larger and more robust, males have a larger leg span. The front pair of legs in particular are longer and are used in capturing prey.
Range length: 4 to 10 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; venomous
Sexual Dimorphism: female larger
As these spiders are nocturnal, hiding in their silken sacs during the day, protecting them from predation, there is currently no information available regarding specific predators of this species.
Males seek out females during breeding season (early summer) and up to 30% of males are killed and eaten by the females after breeding. Females typically mate only once but produce multiple egg sacs (as many as 5, each containing approximately 40 eggs) during June/July; they enclose themselves in the egg sac in order to defend the eggs/young.
Mating System: monogamous
Female yellow sac spiders desposit their eggs in loose silk sacs within their webs in June or July, roughly 14 days after mating. They then stay with their young for roughly 17 days. Males and females typically reach maturity at 119 days and 134 days respectively, though time until maturity varies from 65 to 273 days depending on environmental conditions (temperature, humidity, and day length).
Breeding interval: Breeding occurs once a year, with females depositing eggs 2-5 times during the breeding season.
Breeding season: Late spring to early summer.
Average gestation period: 14 days.
Average time to independence: 17 days.
Range age at sexual or reproductive maturity (female): 65 to 273 days.
Average age at sexual or reproductive maturity (female): 119 days.
Range age at sexual or reproductive maturity (male): 65 to 273 days.
Average age at sexual or reproductive maturity (male): 134 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Females remain in the egg sac for 17 days on average to protect their eggs and young.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Protecting: Female); pre-independence (Protecting: Female)
The Yellow Sac Spider (Cheiracanthium inclusum) is small and pale beige to yellow, often with a tinge of green. A distinctive darker lance-shaped mark runs down the midline of the forward portion of the upper surface of the abdomen. The dark brown chelicerae are large, elongate, and powerful and stand out against the paler body. Body length is around 4.9 to 9.7 mm for females and 4.0 to 7.7 mm for males (Kaston 1978).
Yellow Sac Spiders are often found running about on low trees and shrubs, where they make silken tubular retreats in rolled up leaves. During the day, they typically stay hidden in these retreats, coming out at night to hunt. During the winter, they build their tubular retreats under stones and tree bark.
Yellow Sac Spiders are found throughout most of the United States, with the exception of the northern tier of states (Kaston 1978). Although it has often been stated that their bites pose a danger to humans, the bite is apparently no worse than a bee or wasp sting (Fasan et al. 2008; Vetter and Isbister 2008), although in at least some cases symptoms may be quite unpleasant (e.g., Papini 2012).
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. It is often 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 importance, 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 prosoma (cephalothorax), to sense its environment.[6]
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]
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.
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.
C. inclusum spiders are venomous and capable of biting humans. A bite begins with moderate pain followed by itching. 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]
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. It is a rather small pale yellow species that is indigenous to the Americas. It is often found living in the foliage of forests and gardens but also can inhabit human homes. Despite common beliefs of necrosis, Cheiracanthium bites cause only localized swelling. 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.
