Red-legged purseweb spiders have the largest geographic distribution of all species in the family Atypidae (atypical tarantula), from the southeastern United Sates as far north as Rhode Island and Massachusetts and as far west as Kansas. (Culter, et al., 2006; Hardy, 2003; Hoffman, 2010)
Red-legged purseweb spiders prefer to attach their webs to small hardwood trees. They also form webs on grassy vegetation and non-wooded structures. They primarily live in temperate forests but may also occupy metropolitan areas. Studying this species in the wild can be challenging as they prefer undisturbed woody habitats with good leaf and soil cover, and tend to be solitary and shy. (Culter, et al., 2006; McKenna-Foster, et al., 2011; Reichling, et al., 2011; Wolff, 2005)
All Sphodros have a similar physical appearance, characterized by a stocky, robust body held low to the ground with short, strong legs. In Red-legged purseweb spiders, the body is divided into two segments: the cephalothorax, which is black in color, and the abdomen (also called the prosoma or opisthosoma). As Arachnids, they have 12 appendages total which are connected to the cephalothorax: one pair of chelicerae, one pair of pedipalps, and four pairs of legs. The posterior of the cephalothroax is flattened while the anterior slopes upward. The dorsal plate of the cephalothorax is known as the carapace, and the ventral side known as the sternum. Chelicerae, consisting of two parts (a basal segment and a movable fang) are attached to the front of the carapace. In this species, the chelicerae are oversized (1/2 length of carapace) and are used for capturing prey, defense, and for grasping items. Two pairs of venom glands are located in the cephalothorax, connected to the fangs (used to bite and envenommate prey). Red-legged purseweb spiders have eight black eyes grouped close together on the front end of the carapace and three pairs of abdominal spinnerets used to construct tube-webs. Activities related to reproduction often lead to increases in metabolic rate, with females investing more energy into production of the eggs and males investing more energy in respiration. (Culter, et al., 2006; Foelix, 2011; Gertsch and Platnick, 1980; Hoffman, 2010; McKenna-Foster, et al., 2011; Newton, 2008; Wilder, 2011)
Males are easily distinguishable from females by their crimson red legs. It has been hypothesized that this coloration may be a mimetic or aposematic display, advantageous to wandering males. The carapace is reddish brown to black with several small yellowish spots with chelicerae that often reach the length of the cephalothorax, are almost three times as long as they are wide, broad at the base, and with rough, curved hairs and spines. The abdomen is dull black, oval shaped, and covered with many black hairs. Males can reach up to 14.5 mm in length. (Culter, et al., 2006; Foelix, 2011; Gertsch and Platnick, 1980; Hoffman, 2010; Newton, 2008; Wilder, 2011)
Females can reach up to 25 mm in length, making this the largest Sphodros species. Their chelicerae are about twice as long as they are wide and broadest at the base, similar to the males. The carapace is reddish-brown and their legs are the same color as the carapace, with a dull black to dark brown abdomen. (Culter, et al., 2006; Foelix, 2011; Gertsch and Platnick, 1980; Hoffman, 2010; Newton, 2008; Wilder, 2011)
- Sexual Dimorphism
- female larger
- sexes colored or patterned differently
- male more colorful
- sexes shaped differently
- Range length
- 14.5 to 25 mm
- 0.57 to 0.98 in
Species-specific developmental research is quite scarce for red-legged purse web spiders. In general, the development of a spider consists of three phases: the embryonic, larval, and nympho-imaginal periods. In the embryonic period, an egg is fertilized and the body is formed. During the larval stage, some morphological characteristics are undeveloped and the spiders are unable to feed on their own. In the nympho-imaginal period, organs fully develop. The nymph (juvenile) looks like a miniature adult but it is not sexually mature. This system is known as incomplete, or simple metamorphosis. A juvenile spider grows into an adult through molting, where the exoskeleton is sloughed off between growth phases. Juvenile spiders remain at the site of their first web until reaching maturity, a period of several years. Male red-legged purseweb spiders usually exhibit a change in behavior after their final molt as they begin to search for mates. A closely related species, Sphodros abotti, has been observed laying eggs in August, which hatched in late September. The mean number of juvenile spiders hatched per web found for this species was found to be 79.7. (Culter, et al., 2006; Foelix, 2011)
- Development - Life Cycle
Little is known about the specific reproductive behaviors of American Sphodros species. However, it is well documented that after their final molt, spiders develop pedipalps, an additional pair of appendages. In males, pedipalps are used for storing and transferring sperm while in females the pedipalps are simply shortened legs (not used for locomotion). Males of the related species S. abboti have been observed discovering female tube webs. Tubes of adult female S. abboti webs are hypothesized to be marked with sex pheromones, suggesting that the prime cause of courtship and mating in Sphodros is due to a contact chemical produced by adult females. (Foelix, 2011)
- Mating System
Research on the specific reproductive behavior of Sphodros is very limited. It has been noted that the bottom of the purse web is enlarged; it is in this area that egg sacs are laid and guarded by females. In general, it is well known that spiders are always dioecious, sperm-storing and oviparous. Research has suggested that male red-legged purseweb spiders are diurnal and search for mates in June and it is known that these spiders take several years to reach sexual maturity. (Coyle and Shear, 1981; Foelix, 2011)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- delayed fertilization
- Breeding interval
- Red-legged purse web spiders breed annually.
- Breeding season
- Red-legged purse web spiders likely mate in the summer.
Specific data regarding parental investment is limited for this species. However, it is well known that among spiders, females provide a wide range of maternal care, whereas males do not. This is evident in red-legged purse web spiders, as females spend the entirety of their lives in their tube webs while males wander long distances (up to 200 meters) in search of potential mates. In general, female spiders invest more energy than males in the reproduction process as they must produce eggs, while males invest comparatively little energy in the production of sperm. (Herberstien and Wignall, 2011; Morrow, 1986; Wilder, 2011)
- Parental Investment
- female parental care
Research on the lifespan of this species is limited. Mygalomorph spiders tend to be long-lived, compared to their sister taxa, Araneomorphae. Females can live to seven years or more. The lifespan for males is unknown. ("Spiders", 2012; Culter, et al., 2006; Foelix, 2011)
- Range lifespan
- >7 (high) years
- Range lifespan
Spiders of the family Atypidae are more commonly called “purse-web” spiders due to their unique ability to capture prey using the wall of a silk-tube. These distinctive webs are an effective way to find red-legged purse web spiders. These spiders form vertical tubes by attaching one end to a tree, rock, or concrete wall and the other end into soil several centimeters away. Females spend their entire lives in burrows at the bases of their tubular webs, while adult males do not build webs, wandering long distances in search of potential mates. Webs are widest below and at the surface of the soil, and become thinner and fragile toward the top anchor point. Females can extend their webs a foot or more up the trunk of a tree. The outer side of the web may be covered with soil and debris, camouflaging it. Because this species is rare, little is known about their social behavior. On Tuckernuck Island, Massachusetts, dense populations have been found where this species occurs in groups ranging from small aggregations to large colonies. This may be due to low predation rates on this island. (Coyle and Shear, 1981; McKenna-Foster, et al., 2011)
Female home ranges are typically limited to their webs while males wander over wide areas (up to 200 meters). (Herberstien and Wignall, 2011)
Communication and Perception
Female red-legged purseweb spiders sense prey through vibrations generated on the web and it is hypothesized that males sense female webs through pheromones. In general, spiders communicate during courtship using mechanical, chemical, and visual signals. Hairs present on their legs help spiders to sense their surroundings. (Coyle and Shear, 1981; Culter, et al., 2006; Foelix, 2011; Morrow, 1986)
Red-legged purse-web spiders are predators. Many mygalomorph spiders consume quite large prey, sometimes up to twice their own size, due to the span of their chelicerae. This species typically feeds on a variety of ground surface arthropods including crickets, beetles, wasps, worker ants and caterpillars. Male red-legged purseweb exoskeletons have been found in tube-webs, suggesting that females may consume their mates. This species spins tube webs which, unlike webs designed to trap prey, are non-sticky. Females depend on their speed and alertness to get to a place where an insect is crossing their webs. When prey reach the web, females protrude their oversized chelicerae through the silk and into the prey, then folding their fangs back immediately. Using silk, females pull prey into the tube and immediately repair the hole made from the prey by applying silk from the spinnerets. (Coyle and Shear, 1981)
- Animal Foods
- terrestrial non-insect arthropods
- Foraging Behavior
- stores or caches food
Remains of male red-legged purseweb spiders have been found in tube webs, suggesting that males may fall prey to their mates. These spiders are sometimes eaten by birds, small mammals, and other spiders. Male coloration (deep red legs) may be a form of aposematism, perhaps an advantage for wandering long distances in search of mates. The continued spread of fire ants, a probable predator of this species, may affect populations of red-legged purse web spiders. ("Red-legged purse web spider-Arachnids Reference Library", 2012; Culter, et al., 2006; Foelix, 2011)
- Anti-predator Adaptations
- Known Predators
- Fire ant (Solenopsis)
Red-legged purseweb spiders are known predators of a variety of terrestrial arthropods. In addition, they are prey to birds, small mammals, and other spiders. Beyond this, relatively little is known about how this species impacts the ecosystem. In general, nematodes (roundworms) are known to be parasites of spiders that cause reduction in size of muscles, midgut, and reproductive system. Most spiders die just before or after the parasite exits the body. (Coyle and Shear, 1981; Newton, 2008)
Economic Importance for Humans: Positive
The clearest benefit for humans may be the management of ground level arthropods. These spiders are rarely encountered by humans and are not pests. While venomous, they only serve as a threat to those who are highly sensitive to insect bites. (Coyle and Shear, 1981; Newton, 2008)
- Positive Impacts
- controls pest population
Economic Importance for Humans: Negative
No negative effects are known. (Newton, 2008)
Red-legged purseweb spiders, although scarcely found in nature, are not listed on any conservation lists. (Reichling, et al., 2011)
Audrey Urquhart (author), University of Michigan-Ann Arbor, Jeremy Wright (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
Referring to an animal that lives in trees; tree-climbing.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
- delayed fertilization
a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.
- active during the day, 2. lasting for one day.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- female parental care
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
- internal fertilization
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
chemicals released into air or water that are detected by and responded to by other animals of the same species
having more than one female as a mate at one time
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
- stores or caches food
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
- tropical savanna and grassland
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
living in cities and large towns, landscapes dominated by human structures and activity.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
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