Theridiidae

These spiders build irregular webs and they remain in the web in an inverted position. The legs are moderately to very long and usually without spines, or have no spines on the tibiae and metatarsi. Several species in this family commonly occur in peridomestic and domestic habitats around the world.

American house spider, domestic spider, Achaearanea tepi-dariorum (= Theridium) (Fig. 18.8j) Males are 3.8-4.7 mm long and females are 5-6 mm long. The carapace is yellowish brown and the abdomen is grayish white to brown, with indistinct brown chevrons on the posterior half. Legs of the male are orange; female legs are yellow with brown bands at the ends of the segments. Natural habitats include under stones and boards on the ground. In the urban environment it occurs in barns, unused outbuildings, and houses. Itmakes webs in corners of rooms and frequently in the angles of windows. Adults are present year-round and some individuals live for 1-2 years. Egg-sacs are brown, oval or pear-shaped, 6-9 mm in diameter, and usually placed in the web. Eggs are laid 6-8 weeks after mating; hatching occurs in about 1 week. Females may produce as many as 17 egg-sacs, with a total of 3794 eggs. Female spiders complete development in six molts and males in seven molts. This species is distributed nearly throughout the world. In subtropical regions it occurs outdoors, while in temperate regions it occurs primarily indoors, including greenhouses. Tepidariorum is Latin for hot bath or hothouse. A related species, A.frondeum, occurs indoors in southern USA, from Florida to California.

Florida red widow spider, Latrodectus bishopi Males are about 5 mm and females about 10 mm long. The cephalothorax and legs are reddish orange; the abdomen may be black or have dorsal median red spots which have a yellow border. The venter of the abdomen may have one or two red spots. The species builds nests above ground in tree branches. The webs are large - typically a large-meshed network of thread above a convex sheet. This species occurs in southern USA, primarily southern Florida. Argyrodes spiders are associated with the webs of L. bishopi; the most common species are A. baboquivari, A. elevatus,A.furcatus, and A. caudatus.

Brown widow spider, Latrodectus geometricus This species varies in color from light gray to light brown, and sometimes nearly black. The dorsum of the abdomen has a pattern of black, white, red, and yellow markings. On the venter of the abdomen is an hourglass mark, which is orange or yellowish red. The egg-sac is covered with small spikes. This species is nearly cosmopolitan in peridomestic and domestic habitats. It has been introduced into southern USA and is very common around buildings in South America (Brazil) and South Africa.

Redback widow spider, Latrodectus hasseltii Males are 34 mm long and females are 12-15 mm long. The female body is black and has a red medial stripe on the posterior of the abdomen dorsum, and red spots anterior to the stripe. The venter has several red spots and a large, hourglass-like mark. This species occurs in urban habitats in India, Japan, and Australia. In Japan, it overwinters outdoors behind and beneath vending machines, inside telephone booths, and under benches.

Latrodectus hesperus This species occurs in western USA and western Canada. Females are 14-15.5 mm long; males are 3.8-4.5 mm long and usually light brown. Egg-sacs contain about 196 eggs, they are light brown and about 11 mm in diameter. Hatching occurs in about 14 days; fecundity is about 21 egg-sacs. Adult males live about 196 days, females about 952 days. This species builds webs indoors in corners ofrooms and outdoors in sheds and barns. Webs may be as high as 75 cm above the ground and have a long retreat.

Southern black widow spider, button spider, Latrodectus mactans (Fig. 18.8d, e) Males are about 6 mm long, while females are 10-15 mm long with a leg span of 30-35 mm. Females are shiny black and the abdomen is rounded; typically there is a red double-triangle or hourglass mark, or a similar red mark, on the venter. Red markings usually appear after the second molt but are sometimes absent, especially in immature forms. Immatures have complex patterns of red, white, and orange on the abdomen. The web may be 30 cm wide and nearly as high; it appears to be a random structure, but there is a common structural plan. The female hangs in an inverted position with legs extended. Females do not move far from their web. Latrodectus means robber or biter; mactans means murderous.

Mating occurs in April and May; a single mating is sufficient to fertilize several batches of eggs. Egg-sacs are gray, spherical or globular, about 9.5 mm diameter, and placed in the web. Fecundity for one season is about 10 egg-sacs, with 250-750 eggs per egg-sac; total egg production may exceed 2500. Hatching occurs in 14-30 days, and newly emerged young remain in the egg-sac until the first molt, and sometimes until the second molt. Young spiders are pale brown to reddish brown, and they have a pattern of stripes on the abdomen and alternating bands on the legs. Young spiderlings often use ballooning to disperse. Development is dependent on food and environmental conditions: for males it is 30-100 days and 4-7 instars, for females 60-120 days and 7-9 instars. Spiderlings usually overwinter and become adults the following year. Adult males live 28-40 days and females live 1-2 years.

Natural habitats for this species include around or under logs, tree stumps, and rocks. In the urban environmentitoccurs primarily in peridomestic habitats and rarely indoors. It occurs in downspouts, firewood piles, discarded household materials, electric and water-meter boxes, and near vents and doors in crawlspaces. This species is widely distributed throughout the USA, but it is more common in the southern than in northern states. It also occurs in Mexico, Central and South America, West Indies, and Hawaiian islands.

Prey for this spider is any insect or other arthropod that becomes entangled in the small but efficient web. The spider usually remains at the edge of the web, but responds quickly to any vibration of the strands. It usually approaches the trapped prey backwards while extending a strand of viscid silk, first tying down any moving legs or wings; viscous droplets ofsilk are ejected from the spinnerets to entangle the prey further. The spider delivers a lethal bite to the prey and it quickly dies. Immediately after the kill, the body fluids of the prey are sucked out by the spider. Once the prey is utilized, all points of attachment between its body and the web are cutand it drops from the web. The amount of food eaten varies with environmental conditions. Records for the life of one L. mactans include 250 house flies, 33 fruit flies (Drosophila), two crickets, and one small spider.

Mating habits of this spider are a sequence of movements that ensure the successful transfer ofsperm to the female and safe departure of the male. After becoming an adult, the male leaves its web and seeks a female. When a male encounters the web of a female he moves his abdomen to cause the web to vibrate: the female usually responds with similar movements. The male approaches and strokes the female with his front legs. If the female is receptive the mating sequence proceeds; if not, the male may become prey. The male spins a small web to enclose the female, and then he transfers sperm from either palpus to the female genital opening. The female easily frees herself from the small web and may attack and feed on the male. However, if food is available to the female, the male is not attacked. Males mate several times, but females typically mate only once.

Northern black widow spider, Latrodectus variolus Males are 4.5-8.3 mm long and females are 7.4-13 mm long. The body is glossy black; the dorsum of the rounded abdomen and there is typically has a median longitudinal row of red spots; ventrally there are two transverse red bars (notan hourglass shape). Egg-sacs are gray and about 12 mm in diameter. Fecundity is about six egg-sacs; hatching occurs in about 13 days. Adult males live about 155 days, while females live about 822 days. This species builds webs in the branches of trees, 1-6 m above the ground; it infrequently occurs in peridomestic habitats. Adult males live about 155 days, while females live about 822 days. This species is distributed in northern USA and Canada, and its range in southern USA overlaps with L. mactans.

Other Latrodectus There are about 30 described species in this genus and species are distributed around the world. L. cinctus, the African widow spider, occurs from eastern to western Africa. L. curacaviensis occurs in Brazil, and is a medically important spider in the Amazon. L. tredecimguttatus occurs in Europe and North Africa.

Latrodectism is caused by the bite of Latrocectus species. The venom of these spiders is a neurotoxin and causes paralysis of voluntary muscle groups. The first symptom following a bite is a local swelling; this may develop into a large red area, with some localized skin sweating at the site. Severe pain occurs within 3 h, and this includes pain and rigidity; usually there is pain in the legs and abdomen. Other reactions are shock, fever, nausea, severe headache, elevated blood pressure, difficulty breathing because the diaphragm muscles are contracted, and sweating. In most cases, these symptoms subside in 2-3 days.

Steatoda borealis (Fig. 18.8l) Males are 4.7-6 mm long and females are 6-7 mm long. The carapace is orange-brown with a covering of short setae. The abdomen is purplish brown to black with a yellow anterior margin and yellow median line on the anterior portion. Natural habitats include low vegetation, under bark and stones; in the urban environment they occur in corners of sheds and outbuildings. This species occurs throughout the northern USA.

False black widow, Steatoda paykulliana Males and females are about 7 mm long. Mature females closely resemble the blackwidowspider (Latrodectus mactans), buttheylackredmarks on the venter and the legs are brown with dark banding. The abdomen of the mature female has a red band anteriorly; the immature female has a yellowish-white chevron pattern dor-sally, and there is a narrow white band around the anterior. The web is typically a random scaffolding of threads. Natural habitats include low vegetation and undisturbed areas. In urban environments they occur in unused sheds, outbuildings, and indoors. This spider is frequently carried on agricultural products (fruits), and it is imported into the UK. S. paykulliana is known to bite, and causes temporary illness in children. This species is distributed in the Mediterranean region.

Other Steatoda In the UK and Europe, S. bipunctata occurs indoor in attics and cellars, and on the outside ofbuildings. Natural habitats for this species include hollow trees and under loose bark. Steatoda are carried by commerce to regions outside their normal range. S. nobilis is native to the Canary Islands, but has been reported infesting buildings on the Isle of Wight, UK.

Teutana triangulosa (Fig. 18.8k) Males are 3.5-4 mm long and females are 3.7-5.2 mm long. The cephalothorax is brownish orange and the legs are yellow with yellowish-brown bands at the ends of the segments. The abdomen has a pattern of purplish-brown markings on a yellow background. Indoors it is found in basements or in webs built at the corner ofwin-dows. This species occurs in the USA, from New England south to Alabama and west to Oklahoma and Colorado.

Other Teutana In Germany, T. grossa has been reported only in houses. T. castanea is yellow with dark stripes. It occurs outdoors under rocks and under bridges, and indoors it is found on ceilings and under the eaves. This species is distributed in the USA.

Theridion rupicola (Fig. 18.8i) Males are about 2 mm long and females are 2.3-2.9 mm long. The body color is gray with dark gray and brown markings; the abdomen of the female is enlarged and oval; the spinnerets are located ven-trally. The abdomen has a pointed tubercle at the posterior.

Natural habitats include under stones and boards in woods and around houses. Females make a retreat camouflaged with debris, within which are placed the white to brown egg-sacs. This species occurs in the USA, from New England south to Alabama and west to California.

Indian ornamental, Poecilotheria regalis Males and females are about 12 cm long and have a leg span of 16-18 cm. The body is dark brown, and there are yellowish brown transverse bands on the legs. The ventral surface of the abdomen has a yellowish brown band. Poecilotheria spp. occur in southern and northeastern India and Sri Lanka. This species and others in the genus breed in captivity and are often kept as pets. P.fasciata, a xeric species from Sri Lanka, has been reported living indoors.

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