Written by Gerry Wegner, PH.D. B.C.E.
Body 1/3 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes closely grouped. Abdomen round. Color variable. Legs short and spindly.
More than 230 species of cobweb weavers occur in North America north of Mexico. The American house spider, Parasteatoda (previously Achaearanea) tepidariorum, triangulate cobweb spider, Steatoda triangulosa, northern cobweb spider, Steatoda borealis, and false black widow, S. grossa, rank among the most commonly-encountered spiders in and around buildings. S. grossa is similar to S. borealis but is an introduced species found mainly in southeastern and southwestern coastal states.
Cobweb spiders rest upside—down in the middle of their small to medium—sized irregular webs in corners of porticos, eaves, garages, windows and all indoor areas. Some species hide in a corner or crevice at the web’s edge. Females (larger than males) deposit their eggs in brown, papery silk sacs within the web. Depending on species and climate, theridiids may overwinter as eggs, immatures or adults. Continuous development has been observed in warm climates and indoors.
The bite is similar to a pin—prick and, except for the related hourglass spiders, Latrodectus spp. (see HOURGLASS / WIDOW SPIDERS), the venom usually is not dangerous. Building occupants disdain the unsightly webs.
Body 1/2 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes closely grouped. Abdomen globular. Color variable. Legs spindly; not hairy-looking. A red or orange (sometimes yellow) hourglass marking is apparent on the ventral surface of the abdomen. In some specimens the hourglass is separated into two triangles pointing centrally. Females of the southern and western widows are completely black except for the hourglass and, in some cases, a small red spot just above the spinnerets. Female brown widows may be brown and yeIIowish—tan or nearly black, with the hourglass colored orange. The northern widow has three dorso-medial red spots on the abdomen.
Five species of hourglass spiders occur in North America north of Mexico: the black widow, Latrodectus mactans, western widow, L. hesperus (nearly identical to L. mactans, genetically), northern widow, L. variolus, brown widow, L. geometricus, and red widow, L. bishopi (rarely encountered and only in portions of central Florida). Widow spiders are most abundant in the South and Southwest. In northern climates, widows may overwinter as eggs in silk sacs or as immatures in protective settings.
Like their relatives the cobweb spiders, hourglass spiders rest upside-down in their small to medium-sized irregular webs or hide in corners or crevices at the web’s edge in recessed corners of structures. Outbuildings, sheds, pump and meter enclosures commonly are occupied, as are larger rodent bait stations at building foundation perimeters. Some species build webs under rocks, in hollow trees stumps and among tree bark. Females (larger than males) deposit their eggs in round or submarine mine-shaped silk sacs, within the web.
The bite is similar to a pin-prick and the potent neurotoxic venom causes severe muscle cramping, fever and nausea which persist for a day or two. Death rarely results.
Body 1/10 – 1/3 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: Pholcus and Physocyclus spp. have eight small eyes closely grouped: the anterior median eyes are especially small and are separated; while the slightly larger anterior lateral eyes and posterior eyes form two triads (clusters of three eyes) on either side of the carapace. Spermophora spp. have six eyes grouped in two triads. Body brown, beige and gray, typically; Spermophora spp. pale and translucent. Legs long, spindly and banded at joints.
The adult female long-bodied cellar spiden Pholcus phalarigioides, has a body measuring 1/3 inch long. Of the 40 U.S. pholcid species, arguably it is the most frequently-encountered cellar spider in buildings. Often this species is referred to as a “daddy long-legs” by the general public; however this common name contributes to confusion with the garden daddy—long-legs or harvestmen of Order Opiliones, which are not spiders. The round-bodied cellar spider, Physocyclus globosus, and short-bodied cellar spider, Spermophora meridionalis, are smaller (bodies 3/16 inch and 1/10 inch long, respectively) and occupy buildings as well.
Long-bodied cellar spiders build their large, irregular webs in basements, crawlspaces, garages and dark corners of living and work spaces. They rest upside—down in their webs and will shake themselves quickly back and forth in their webs when disturbed. Females (larger than males) carry their round egg sacs in their jaws. Pholcids may overwinter as eggs, immatures or adults in sheltered settings in northern ,climates; however, continuous development has been observed in warm climates and indoors.
The bite is not painful nor is the venom dangerous, contrary to urban myths being circulated via the Internet. Building occupants disdain the large, unsightly webs, which make excursions into basements, cellars and crawlspaces unpleasant.
Body 1/3 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: six small eyes grouped in three diads (close pairs). Dark brown violin pattern on light brown carapace (most distinct in adults). Legs: long and slender. Abdomen: oval; light brown; not hairy-looking.
Three species in North America north of Mexico. The brown recluse, Loxosceles reclusa, and Mediterranean recluse, Loxosceles rufescens, are encountered most often in buildings in the South and where introduced sporadically in the northern U.S.
Brown spiders rest in attics, crawl spaces, basements, wall voids, upholstered furniture, clothing, among items stored in cardboard boxes indoors and under stones in warm climates outdoors. Brown spiders prey on small, soft-bodied insects. They may entangle live prey on a small mat of sticky silk or they may wander at night (also dimly lit rooms during the day) and utilize recently-killed insects as food. Sicariids exhibit continuous development in warm climates and indoors. In northern climates, they may overwinter as eggs, immatures or adults in protective settings.
Brown spiders may invade buildings from outdoors in warm weather and within their species range. They may also be carried into buildings in boxes, furniture and rolled carpets any time of the year. The bite is not painful but the venom is a potent cytotoxin, causing an enlarging necrotic sore that heals with difficulty. Many medical conditions routinely are misdiagnosed as loxoscelism, including secondary , bacterial infections (e.g., MRSA lesion, syphilitic chancre), diabetes ulcers, Herpes sores/blisters, Erythema multiforme (allergic reaction to medication expressed dermally), Pyoderma gangrenosum (immune system dysfunction), Lymphomatoid papulosis (a cutaneous lymphoma—like eruption), localized vasculitis (inflammation of the blood vessels), and squamous cell carcinoma (a form of skin cancer).
Body 1/10 – 1/2 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes in two rows or flat oval pattern; Abdomen: flat oval or irregular disc-shaped. Cephalothorax and abdomen appear smooth. Legs: with sparse hairs and spines on segments closer to body; front pair usually larger than hind pair; held crab-like with all four pairs or all but hind l pair facing fonivard. Color: the misumenoid flower spiders (‘|’homisidae) often are brightly colored; while most other thomisid _ genera and philodromid crab spiders tend to be more subdued combinations of black, gray, white, brown, rust, beige and yellow. Thomisid crab spiders have the second pair of legs shorter than the first pair and include the colorful flower spiders, Il/Iisumena, Misumenops and Misumenoides spp. and the darker bark crab spiders of the genera Xysticus, Bassaniana and Codarachne. Philodromid or running crab spiders have the second pair of legs longer than the first pair .
More than 200 species of crab spiders occur in North America north of Mexico.
Crab spiders are passive hunters, waiting in ambush for prey and relying on their excellent camouflage. They await prey on flowers, leaves, bark, the ground, structural surfaces and in crevices. In most cases, crab spiders overwinter as eggs or immatures.
Usually, crab spiders are associated with exterior surfaces of buildings and the landscape; although they occur indoors occasionally. Flower spiders may be brought indoors inadvertently on cut flowers. To the untrained eye, some philodromid species may be confused with sicariid brown spiders, in a resting , posture. Bites are rare but may be compared to a pin prick or minor bee sting and the venom usually is not dangerous to humans.
Body 3/4 — 1 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: anterior and posterior median eyes smaIl*; anterior and posterior lateral eyes slightly larger. Abdomen: elongate-oval. Legs: long with hairs and spines. Color: brown and beige.
A few species of giant crab spiders occur in North America north of Mexico. The huntsman or housekeeping spider, Heteropoda venatoria, is common in Florida; the golden huntsman spider, Olios fasciculatus, occurs in the West and Southwest.
Giant crab spiders actively hunt for prey (including cockroaches) at night. During the day they rest in crevices, both indoors and outdoors. These spiders are fast runners when disturbed. Sparassids are warm climate spiders exhibiting continuous development.
The bite is similar to a bee sting but the venom usually is not dangerous to humans. Short-term swelling (purplish blotch) and soreness may persist for several days. At night these large spiders frequent walls and ceilings in homes that are not tight. They are not aggressive towards humans and are reluctant to bite. *The anterior median eyes of Olios spp. are relatively large.
Body 1/10 – 1/2 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes grouped in two rows. Abdomen elongate-oval. Body and legs sparsely covered with small hairs or spines. Color: black, brown, tan or yellow; some species with light or dark markings. Many species lightly colored.
More than 200 species of sac spiders occur in North America north of Mexico. The agrarian sac spider, Cheiracanthium inclusum (native) and yellow sac spider, Cheiracanthium mildei (imported), occur across the U.S. and are the most structurally invasive sac spiders. Cheiracanthium species are considered by some specialists to be in the Family Clubionidae, and by others, in the Family Miturgidae. Trachelas species and most ant mimic spiders have been moved from the Family Clubionidae to the Family Corinnidae.
Sac spiders actively hunt for prey at night. During the day they rest in silken retreats under stones, bark and folded leaves outdoors and in corners, folds in fabric and dark recesses indoors. Females guard their eggs within dense silken retreats. Sac spiders overwinter as subadults (final immature stage) outdoors in silk retreats beneath stones, logs and debris.
Yellow sac spiders are active indoors year-round, where they are seen at night on walls and ceilings. Occasionally broad-faced spiders are encountered indoors. The bite is similar to a pin-prick but the venom usually is not dangerous to humans. Occasionally short-term swelling and soreness or a small necrotic wound may result. Secondary bacterial infections from bites are possible.
Body 1/4 — 1/2 inch long. Jaws (chelicerae) move side to side, scissors—|ike. Eyes: eight small eyes closely grouped. Abdomen elongate with pair of long spinnerets. Color: brown and yellow, beige or greenish-yellow; some species with dark markings. Very similar to sac spiders (Families Miturgidae and Clubionidae).
A few species of ghost spiders occur in North America north of Mexico. The yellow ghost spider, Hibana (Aysha) velox, garden ghost spider, Hibana gracilis, and green ghost spiden Wulhla albens (prev. alba), occur in the southeastern U.S. andare common in Florida.
Ghost spiders actively hunt for prey (insects and smaller spiders) at night. During the day they rest in silken retreats under stones, behind bark and in folded leaves outdoors; also in protected corners and crevices of buildings. Ghost spiders can be seen year—round in Florida and the South but are most abundant in spring and summer. In colder climates, they overwinter as immatures or subadults (final immature stage).
The bite is similar to a pin prick or bee sting but the venom usually is not dangerous to humans. Occasionally short-term swelling and soreness or a small necrotic wound may result.
Body 1/2+- inch long. Jaws (chelicerae) move side to side, scissors—like. Eyes: eight small eyes closely grouped. Abdomen elongate with pair of long spinnerets. Legs and body of similar length. Legs and carapace may appear velvety or glossy. Color: black or brown; some species with light markings.
About 250 species of ground spiders occur in North America north of Mexico. The parson spider, Herpyllus ecclesiasticus, occurs in the eastern U.S. and is recognized easily by the characteristic white pattern on the black abdomen. The variegated ground spider, Poecilochroa variegata, is similar. The two-striped ground spider, Cesonia bilineata, with its paired longitudinal black stripes, looks superficially like a small grass spider (Agelenidae) or wolf spider (Lycosldae) but is free-wandering and has the spinnerets and eye pattern distinctive to gnaphosids. Rustic ground spiders, Callilepis species, have the cephalothorax and legs glossy reddish—orange and the abdomen with variable bluish—black or grayish—black bands or patches interspersed with tan.
Some ground spiders actively hunt for prey at night and rest beneath stones and loose bark during the day while others spin small irregular webs beneath stones, bark and leaf litter. Females attach their disc-shaped white or pink egg sacs to surfaces in the concealed resting sites. Some species overwinter as adults while others overwinter as immatures.
The bite is similar to a pin-prick or bee sting but the venom usually is not dangerous to humans. Occasionally some species are found on floors and walls indoors.
Body 1/5 — 3/4 inch long and stocky. Jaws (chelicerae) move side to side, scissors-like. Eyes: four large anterior eyes, especially large median pair; four small posterior eyes, widely spaced. Vision excellent for discerning shape, color and movement. Abdomen: oval; covered with hairs. Variously-colored markings on black, gray, brown or beige (rarely green) background. Legs: about as long or shorter than body; stocky with dense hairs and spines in most species; front pair (especially those of males) often larger than other legs. Some species are ant mimics.
About 300 species ofjumping spiders occur in North America north of Mexico. Among the most encountered species around and in structures are the Phidippus jumping spiders (e.g., the daring jumper, Phidippus audax) and the zebra jumper, Salticus scenicus.
Jumping spiders are active hunters, moving with short, quick hops. They stalk prey during the day on open surfaces. Males perform courtship “dances” for females prior to mating and often serve as a post-copulatory meal to hungry females. Concealed silken tube-like retreats serve as sites for molting, egg protection and overwintering. Depending on species and location, jumping spiders may ovenwinter as adults, immatures or sometimes as eggs.
The bite is similar to a bee sting and the venom usually is not dangerous to humans. Jumping spiders are active on exterior walls and window screens; also on tree trunks, logs and rocks. Sometimes they hitchhike indoors on people and pets.
Body 1/4 – 1 1/3 inches long. Jaws (chelicerae) move side to side, scissors—like. Eyes: four anterior eyes small; posterior median eyes large; posterior lateral eyes smaller and set back. Abdomen elongate. Color: black, brown, tan, gray or yellowish; often with lighter or darker markings. Spinnerets are small. Legs long, fuzzy—Iooking and spiny; sometimes banded. Similar to nursery web spiders.
About 200 species of wolf spiders occur in North America north of Mexico. The largest native wolf spider is Hogna carolinensis but is rarely seen around structures. A large, structurally invasive wolf spider, Hogna helluo, is common in much of the U.S. Another rural peridomestic species, the rabid wolf spider, Rabidosa rabida, has a yellowish-tan base color with paired medium-brown stripes on the carapace and a medium-brown middorsal stripe, edged with black markings, on the abdomen. The dotted wolf spider, Rabidosa punctu/ata, is similar to R. rabida except the dorsal stripes are dark brown (nearly black) and the light colored underside of the abdomen is punctuated with black spots. The pirate wolf spiders, Pirata spp., and pardosas, Pardosa spp., are smaller wolf spiders that occur in rural settings.
Wolf spiders actively hunt for prey on the ground and rest beneath stones and debris. Females carry their round, white egg sacs protectively attached to the spinnerets. Hatchling spiders ride piggy-back on their mother until old enough to fend for themselves. Wolf spiders may overwinter as eggs, immatures or adults in the wild. Activity may persist through winter indoors.
Depending on the species, the bite is similar to a pin-prick or bee sting but the venom usually is not dangerous to humans. Temporary numbness or secondary bacterial infections from bites may occur. Larger species are among the most feared of invasive spiders due to their large size and hairy bodies.
Body 1/4 – 1 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: four anterior eyes small; four posterior eyes larger. Abdomen oval. Color: black, brown, tan, gray or yellowish; often with lighter or darker markings. Several tropical species have the “face” (anterior carapace), fangs (chelicerae) and sometimes the pedipalps colored some combination of red and black. The legs are long, fuzzy—looking and spiny. Wandering spiders are similar to nursery web spiders and wolf spiders in general appearance.
About 550 species of wandering spiders occur worldwide in the tropics and subtropics; but the American wandering spider (a.k.a. Florida false wolf spider), Cterius hibernalis (possibly synonymous with Ct. captiosus), is the one representative found in and around homes built in wooded areas throughout peninsular Florida. It is large, dark brown and has a broad pale, full-length central pale to yellowish stripe. Two genera of wandering spiders that sometimes make their way into the U.S. from Central and South America, hiding in bunches of imported bananas and other cargo shipments, are Cupiennius (harmless or of questionable concern) and Phoneutria (potentially dangerous).
Wandering spiders actively hunt for prey on the ground, vegetation and around structures. Adults are found in the spring and summer; large subadults are reported during fall and winter.
The bite is similar to a bee sting and the cytotoxic—neurotoic venom may cause a necrotic wound aswell as disorientation and other (sometimes prolonged) neurological effects. Envenomation by some Phoneutria spp. can be fatal.
Body 1/2 — 1 inch long. Jaws (chelicerae) move side to side, soissors—like. Eyes: tour small anterior eyes; four slightly larger posterior eyes. Abdomen elongate. Colored tan/beige and brown; often with gray and white markings. Legs long, fuzzy-looking and spiny; often banded. Similar to wolf spiders.
About 15 species of nursery web spiders occur in North America north of Mexico. The brown, yellow-tan and gray forest nursery web spiders, Dolomedes tenebrosus and D. scriptus and the brown, gray and white six-spotted fishing spider Dolomedes triton, are large rural examples in the Midwest and eastern U.S.
Nursery web spiders may rest motionless for hours, with their legs stretched outward, on sun—lit vegetation, tree trunks (especially near deep scars and hollows), building exteriors or the ground during the day. Those favoring lake and pond shoreline habitats rest on cattail stems and aquatic vegetation. Periodically they may hunt actively for prey. Females carry their round, white egg sacs protectively in their jaws. Pisaurids overwinter as subadults (final immature stage) and adults.
The bite is similar to a bee sting but the venom usually is not dangerous to humans. The large size of these impressive spiders invokes fear responses in arachnophobes.
Adult body 1/3 – 1/2 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight similar-sized eyes; anterior median pair more closely spaced than posterior median pair; anterior and posterior lateral eyes nearly joined. Cephalothorax mostly smooth with a glossy appearance. Abdomen: oval and velvety — covered with short hairs (setae). Color: reddish-brown to black with beige markings (Amaurobius and Callobius spp.) or yellowish—brown with gray markings (Coras spp). Legs: longer than body; hairs and spines sparse on leg segments close to body and more dense on outer leg segments. Anatomy similar to that of funnelweaver spiders (Agelenidae) and wolf spiders (Lycosidae) but have a cribellum (small, sieve-like plate in front of the spinnerets, on the underside ofthe abdomen) and a different eye pattern.
83 species of hackledmesh weavers occur in North America north of Mexico. Among the most encountered species in and around structures are the medicinal web spider, Coras medicinalis(previously placed in Family Agelenidae), black Iace—weaver, Amaurobius ferox, and Bennett’s hackledmesh weaver, Callobius bennetti.
Hackledmesh weavers prefer cool, dark settings near ground level. They rest and ensnare prey on loose, coarse webs spun outdoors under logs, stones and debris piles and indoors in dark corners and under objects on floors in garages, basements, crawlspaces, boiler rooms and tunnels. Silk may be bluish in color. Eggs usually are produced in mid-summer. Hackledmesh weavers overwinter as adults or subadults (final immatures) in outdoor settings.
Can be alarming when discovered indoors. Sometimes captured on sticky traps. The bite is similar to a bee sting and the venom usually is not dangerous to humans.
Body 1/3 — 3/4 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes closely grouped atop a darker, teardrop-shaped raised area on the carapace. Four anterior eyes slightly larger than four posterior eyes. The anterior lateral eyes are forward of the anterior median eyes; while the posterior eyes are in a row. The legs are long and velvety and the pedipalps are noticeably long. The carapace is shiny with sparse hairs. The abdomen is oval and has a velvety appearance. Males are smaller, have longer, thinner legs and are colored yellowish brown to darker brown; while females are larger, stockier and colored grayish brown to charcoal gray. Crevlce weavers have a cribellum (small, sieve—Iike plate in front of the spinnerets, on the underside of the abdomen). Females have a calamistrum (metatarsal comb on the fourth pair of legs) but lack an epigynum (small, hardened plate with paired genital openings ventro-medially on the abdomen).
Seven or more species comprise three genera of crevice weaver spiders inthe southern and southeastern U.S. The most-encountered species in and around human dwellings and barns is the crevice spider (a.k.a. southern house spider), Kukulcania (formerly Filistata) hibemalis. Filistatids are warm climate spiders exhibiting continuous development.
Crevlce weavers create prominent, coarsely-hackled, circular webs surrounding a central opening to the tubular retreat. During the day crevice weavers are in their retreats.
Crevice weavers prefer to occupy the exterior walls of rustic outbuildings, barns, and abandoned and unkempt homes, as well as undisturbed attics and basements. The large size of these spiders may be distressing to arachnophobes. The bite may be similar to a bee sting but the venom is not considered to be dangerous to humans.
Body 1/2 — 3/4 in. long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes closely grouped in a flattened oval or sideways “D” pattern. Abdomen elongate with a pair of long spinnerets. Colored yellowish-tan and brown. Legs long, fuzzy-looking and spiny, ending in three claws.
About 300 species of funnelweavers occur in North America north of Mexico. Several species are European in origin. The grass spiders, Agelenopsis and Agelena species and barn funnelweaver (a.k.a. European house spider or domestic funnelweaver), Tegenaria domestica, are commonly found in and around buildings. The hobo spider Tegenaria agrestis, occurs in the Pacific Northwest and has a (debatable) reputation for being aggressive.
Funnel weavers rest inside the tubular corner of their funnel-shaped webs during the day. At dusk, the spiders place themselves on the outer triangular sheet-like portion of the webs. Webs may be found close to building foundations outdoors on shrubs, ivy, tall grass, decks, and in window wells and recessed vents. Indoors, webs are found in the corners of garages, basements and crawlspaces. On occasion, relocating females and males searching for mates may be found wandering about or resting beneath items on basement and garage floors. Funnelweavers overwinter as eggs in the wild; however, development and activity may be observed indoors, year-round.
The bite is similar to a pin-prick or bee sting and the cytotoxic venom of some species may cause necrotic skin lesions. Secondary bacterial infections from bites are possible.
Body 1/2 inch long. Jaws (chelicerae) are long and move side to side, scissors-like. Eyes: six small eyes closely grouped in , three pairs (diads), forming a tight triangle. Abdomen underside has four respiratory slits, arranged in pairs on either side.
A few cell spider species and six species of tube spiders occur in North America north of Mexico. The woodlouse hunter, Dysdera crocata and the brown tube spider, Ariadna bico/or, are most often encountered.
Woodlouse hunters live under stones, logs, bark, etc. Some species hunt at dusk by sense of touch. Others trap prey on sticky strands that radiate from the tubular silken retreat. They prey on sowbugs, pillbugs, beetle larvae, crickets and earwigs. Dysderids and segestriids typically overwinter as adults in protective settings.
Woodlouse hunters may be found close to building foundations, in basements and crawlspaces, and under landscaping features. The bite can be painful but the venom usually is not dangerous. Secondary bacterial infections from bites are possible.
Large spiders; body 1 1/2 — 2 inches. Jaws (chelicerae) move up and down, opening forward. Eyes: eight small eyes grouped in a cluster. Body and legs usually hairy. Color: mostly black, brown and beige in North America north of Mexico. Body and legs usually hairy. Representative species of the Southwest are the Mexican redrump (black velvet) tarantula, Brachypelma vagans (also in Florida), desert (Arizona) blonde tarantula, Aphonopelma chalcodes, Texas brown tarantula, Aphonopelma hentzi, and California desert (ebony) tarantula, Aphonopelma eutylenum. Similar families: smaller, reclusive mygalomorphs, rarely encountered on developed properties, are the trapdoor spiders (Families Ctenizidae and Cyrtaucheniidae), folding door trap—door spiders (Family Antrodiaetidae), and purseweb spiders (Family Atypidae). Females measure 3/4 – 1 1/3 inches long; , legs shorter than body; cephalothorax and legs smooth and shiny or sparingly setose-spiny; abdomen velvety, smooth, finely wrinkled or ridged.
40 species in the U.S.; occur mostly in the Southwest.
Tarantulas in the U.S. live on the ground and in burrows. They hunt at dusk by sense of touch. Tarantulas spin mats of silk and may line their burrows with silk. They prey on insects, other arthropods, small reptiles, young mice and are most commonly found in early fall. Tarantulas are long-lived (especially females) and survive cold weather in protective settings as juveniles and adults.
Occasionally tarantulas enter open structures and may be found under landscaping features. They defend themselves by “throwing” hairs (quickly rubbing urticating setae from the abdomen using the hind legs), assuming a threatening posture (with forelegs, pedipalps and chelicerae uplifted menacingly), lunging and biting. The bite can be painful but the venom (of U.S species) is not considered to be dangerous. Secondary bacterial infections from bites are possible.
Body 1/3 – 1 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes widely grouped. Abdomen round to heart-shaped. Color variable. Legs usually banded and spiny.
About 180 species of orbweavers occur in North America north of Mexico. The barn spider, Araneus cavaticus, shamrock spider, A. trifolium, marbled orbweaver, A. marmoreus, cross spider, A. diadematus, tropical orbweaver, Eriphora ravilla, and furrow spiders, Larinioides cornutus and L. patagiatus, are among the most commonly encountered orbweavers on buildings and landscaping. (The garden spiders of the Genus Argiope are discussed separately.)
Orbweavers rest head-down in the center or in sheltered corners of their large orb-shaped webs. The webs are constructed at night across porch balustrades, posts, doorways, windows and between branches. Females (larger than males) deposit their eggs in large papery silk sacs, within the web in early autumn. Most species overwinter as eggs and the young emerge in spring. Spiderlings disburse by spinning out long strands of silk and riding on the wind in a process called “ballooning”. As a result of strong updrafts, orbweavers can be carried to the tops of tall buildings, where abundant webs may be observed, especially around lighting, in summer and fall. Some species overwinter as immatures and adults.
The bite is similar to a bee sting but the venom usually is not dangerous. Building occupants find the webs unsightly and often are frightened by these large spiders during late summer.
Body 2/3 – 1 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes widely grouped. Abdomen oval to shield-shaped with yellow, black and silver-white patterns. Legs banded.
The two most common garden spiders that occur in North America are the black and yellow argiope or golden garden , spider, Argiope aurantia, and banded garden spider/argiope, A. trifasciata. The silvered garden spider or silver argiope, A. argentata, inhabits the South and Southwest, from Florida to California. The Hawaiian argiope/garden spider, Argiope appensa, has a pentagon-shaped abdomen and a very ornate black and white pattern on its cephalothorax. This species not only inhabits the Hawaiian islands but Taiwan, Indonesia-New Guinea and the Mariana Archipelago as well.
Garden spiders rest head-down in the center of their large orb—shaped webs. Garden spiders typically create a dense, zigzag pattern (stabilimentum) of sticky silk near the center of their webs. The webs are constructed at night between branches, tall woody-stemmed weeds and sometimes on buildings and other manmade structures. Females (larger than males) deposit their eggs in large papery silk sacs, within the web in early autumn. Eggs overwinter and the young emerge in spring.
The bite is similar to a bee sting but the venom usually is not dangerous. Homeowners and building occupants find the webs unsightly and often are frightened by these large spiders during late summer and autumn.
Body 1/3 inch long (Leucauge species) to 1/2 inch long (Tetragnatha species). Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes. The orchard orbweavers of Genus Leucauge have the lateral eyes grouped as well as the anterior median pair; while longjawed orbweavers of the genera Tetragnatha and Pachygrrafha have the eyes more widely spaced. Abdomens of tetragnathids are elongate oval. North American Leucauge spp. are black, silvery-white, yellow, orange, brown and green. Legs are long, slender, spiny and translucent. Tetragnatha species are mainly brown, yellow and silver and rest with legs held together frontward and rearward.
About 170 Leucauge species occur worldwide and are most abundant in tropical and subtropical regions. The mabel orchard spider; Leucauge venusta, (syn. L. mabe/ae), is found in the eastern U.S. A slightly larger; less colorful orchard spider Leucauge argyra, occurs in Florida but is less frequently encountered than L. venusta. About 250 Tetragrratha and Pachygnatha spp. occur worldwide, over a dozen of which can be found in North America. The guatemalan longjawed orbweaver, can be sporadically abundant in the eastern, southeastern, southwestern and lower midwestern U.S.
Orchard orbweavers rest upside—down in the middle of their horizontal or angled orb-shaped webs. The webs are constructed at night among tall vegetation and on protected structural features. These common spiders may be found year-round in warm climates. In northern climates, tetragnathids overwinter as eggs or immatures, depending on the species.
The bite is similar to a pin-prick or bee sting and usually is not dangerous. Orchard orbweavers and their webs often occur shrubs by buildings and on sheltered exterior features of buildings. Tetragnatha and Pachygnatha spp. prefer identical settings close to water: T. guatemalensis, where numerous, can create massive communal webs.
Body 3/4 to 1 inch long. Jaws (chelicerae) move side to side, scissors-like. Eyes: eight small eyes. Niphilid spider eyes are grouped like those of tetragnathid spiders. This similarity, in addition to the presence of massive, somewhat elongate chelicerae and an elongate abdomen, caused nephilids to be placed with the tetragnathid Iongjawed orbweavers until recently. Adult females may have a leg span of three inches or more. Tufts of long hairs (setae) on the femur and tibia segments of the legs, near the outer joints, give these large spiders a “fuzzy—kneed” appearance. The golden silk orbweaver, Nephila c/avipes, has a mainly silvery-white carapace, dotted with black and having a black face and jaws. The abdomen is golden yellow, symmetrically dotted with small white spots. The legs are yellow and black. The large orb webs may span several feet from tree to tree. The silk is a unique golden color. At first glance, nephilid orbweavers look much like the large garden spiders of family Araneidae.
Although several Nephila species occur worldwide, the most-encountered New World species is the golden silk orbweaven Nephila clavipes. This species is common in tropical and subtropical South, Central and North America. It is found sporadically in the Southeastern U.S. Localized populations may be large in the preferred settings.
Nephilid spiders prefer undisturbed wooded settings bordered by low vegetation, marshy areas and bodies of water. Sometimes webs are constructed among trees and shrubs near buildings. Like the Argiope garden spiders, nephilid , females await prey suspended in the middle ofthe large orb webs. Soft-bodied flying insects comprise the primary diet of these spiders. Successive generations occur in the tropics.
Can be alarming when discovered abruptly near buildings or encountered, mid-web and mid-trail, by walkers and joggers. Bites resulting from accidental encounters are not considered to be dangerous but may be painful — similar to a bee sting.
An integrated approach to spider management includes preparatory, cultural, physical/mechanical and chemical aspects:
A thorough inspection of the premises and structure(s) is the first step towards determining the scope of infestation and conditions conducive to spider entry. Spider specimens should be taken and identified to determine whether or not a threat to occupant health and well—being exists.
Those responsible for landscape management should prune tree and shrub branches away from structural surfaces to prevent spiders and other pests from bridging onto buildings. Likewise, tall vegetation, such as flowers, groundcover, ivy, turf grass and weeds, should be cut down and removed from along the foundation perimeter, porches and entrances of buildings. Stacks of firewood and other materials should be relocated away from buildings. Outdoor lighting on structures should be converted from white incandescent and mercury vapor lamps (attractive to insects — spider food) to yellow amber incandescent and sodium vapor lamps (less attractive to nocturnal flying insects, thereby reducing prey for spiders).
Those responsible for structural maintenance should perform repairs of damaged and loose-fitting doors, windows, screens, vents, roofing, flashing and exterior sheathing. These exclusion or pest-proofing measures are very important for preventing spiders and other pests from entering structures.
Sticky traps and pest monitors should be placed indoors along exterior walls cf attached garages, basements, crawl-spaces and living spaces where spiders are active. Sticky monitors should be placed beneath furniture believed to be occupied by reclusive spiders. A shop vacuum or portable vacuum fitted with hose attachment can be used to remove spiders and webs from furniture, corners, sill plates, joists and other indoor structural features. A dusting tool fitted with telescoping handle can be used for web removal.
Exterior perimeter treatments of building foundations and upper structural recesses and features can be made with label-rate applications of residual liquid insecticides. Microencapsulate (ME/CS), suspended concentrate (SC) and wettable powder (WR, WSP) formulations currently provide acceptable long-term protection against invasive spiders. Indoor control of spider infestations will be enhanced with insecticide spot treatments directed at basement and crawlspace sill plates and upper corners of attached garages and living spaces. For this purpose, appropriate formulations of synergized pyrethrins or residual liquid insecticides should be applied as an aerosol (at close range) or fan spray from a pressurized sprayer, taking care to avoid contamination of non-target areas and surfaces. Additionally, structural voids can be injected with residual insecticide dusts that have been labeled for use against spiders.