The genus Latrodectus (family Theridiidae, the cobweb weavers) is represented in North America by five species known as the widow spiders. In Europe, at least three species of Latrodectus are found; Latrodectus tredecimguttatus, Latrodectus pallidus, and Latrodectus geometricus. These species are known by various common names in different countries. Latrodectus pallidus is found from Libya north to Russia, while L. geometricus is found in European countries bordering the Mediterranean, also occurring in warmer countries throughout the world. The most widely distributed species in Europe proper is L. tredecimguttatus, which is found from the west coast of Spain, east to China, and south into Africa. The species has been collected as far north as north-western France near the coast.

The name “widow” is a misnomer, since until recently, in only a single species (Latrodectus hasselti from Southeast Asia, Australia, and New Zealand) of the 30 species world-wide does the female routinely kill or injure the male during mating. Almost all of the different species of widow males studied so far are adept at escaping the female’s clutches. Many, however, still refer to the genus as black widows. The name black widow is doubly inappropriate since many, if not most, are not black (one species in the Middle East is white to creamy yellow; a white widow?). In Africa, especially South Africa, the genus is more popularly referred to as the button spiders. In Australia, they are called red-back spiders, although this name may be intended solely for L. hasselti.

At one time, all North American widows were placed in one species, Latrodectus mactans (Fabricius) with subspecies representing what are now accepted species in their own right. Widow spiders are physically the largest members of the cobweb weaver spider family, a large family of more than 2,200 species. Currently, 107 other spider families are recognised (order Araneae).

Who “Widowed” The Widow Spiders?

In real life, only a fraction of widow males end up as the female’s feast after the fact. The majority of them drop from the web when finished with their mating duties and head out looking for the next female. Some males (in nature, not captivity) may stay around the periphery of the female’s web for weeks. So how did this malicious myth get started? Around the turn of this century, the famous entomologist, John Henry Comstock, began to mention and write about black widows, a name he probably coined. The name crept into the literature initially in his first edition of “The Spider Book” (1912). The following is probably what Comstock did that motivated him to invent the name.

In around 1900, Comstock (or someone he knew) caught, or was given, one or more widow spider females. Since nobody wanted what was, even then, suspected of being potentially dangerous animals running about, Comstock put them in escape-proof cages, where they built webs. Next, he acquired a male widow(s) and before long he had it mating with the female(s). Understandably, he just didn’t want to put his hand in the cage to get the male out after he was done, so he left him in there until the female finally snared and munched down on him (this could have taken weeks).

Comstock never knew it, but he had started a time-honored tradition in the science of arachnology. Soon, widow researchers all over the world were sticking males and females together in escape-proof cages and waiting until one of them bought it. Later, many arachnologists began paying lip service to the notion that widow females didn’t really eat their mates most of the time. This notion turned out to be the correct one. Males are not in great danger from the female while mating. Impaired males, or males under poor nutritional conditions, are more susceptible to becoming prey, but this goes for most spider species. What is the major mating danger to macho male widow spiders? Escape-proof cages.

The Mating Process

The following description applies primarily to L. mactans, but most other widow species use similar methods. The last moult of widow spiders brings them abruptly into adulthood, or the ultimate instar. Unlike many primitive mygalomorph spider females, and a few other advanced species, they will never moult again. A few exceptions have been noted for females moulting once more after the ultimate instar in captivity.

Shortly after the final moult, the male builds a simple sperm web, deposits a drop of sperm onto it from the testes located in its abdomen, then siphons it into his pedipalps. The pedipalps of adult male spiders serve as intromittent, or secondary, sexual organs. The males are now ready to seek out females.

The female probably incorporates a pheromone into her web that tells the male that she is the right species and what he’s looking for. Upon contact with her web, the male receives a set of instructions, or prime releasers, triggering his genetically controlled courtship behaviour. He begins a cutting sequence, often lasting an hour or more, in which he cuts away and wraps large sections of the female’s web into bands, balls and sheets with his own silk. Since the female is poor-sighted and depends upon touch to know her location in her web to catch prey, the cutting may be the equivalent of “blinding” the female, giving the male an added escape advantage in case of attack.

From the first touch of her web, and throughout the cutting sequence, the male vibrates his abdomen, sending signals to her through her web that pacify the female. This reduces the chances of her attacking the male and has the effect of placing her into a “trance.” The male will slowly approach the female, still vigorously vibrating his abdomen. He will then begin to spin the “bridal veil” around her, a thin trace of silken strands that she is capable of breaking effortlessly. The purpose of the veil is probably to further placate the female. Perhaps it reassures her that he is the correct species (should male pheromones be present in the silk) instead of arresting her movements in any significant manner.

With his veil complete, the male closes in. After first contact, he taps and probes with his pedipalps on the abdomen of the female, who hangs inverted in her web. If she remains in a tranquillised trance, he will insert the tip of one embolus of a pedipalp at a time into her bursa, the openings of her genitalia, to inseminate her. Insemination takes anywhere from a few seconds to a few minutes. When finished, the male rapidly drops out of the web. He may continue to stay close to her web for a time, or may go off in search of other females. Southern black widow males (and probably most of the remaining widow species) are capable of multiple matings, although multiple mating by widow spiders was thought impossible by arachnologists until the mid 1980’s.

Mating is not always as easy and straightforward as described above. Once he inserts it, the male can’t immediately remove his embolus and drop away should the female suddenly awaken from her “trance.” This is probably the most dangerous time for the male. The female may also decide to resist all the male’s attempts to mate. He may leave, or he may stay out on the periphery of her web (observed in one case for nearly two weeks) and keep trying. Male widows occasionally do get eaten by the larger females, as do males of many other spider species. Spiders are a group of ferocious, proficient predators, and as such, mistakes are made and males will occasionally be eaten.

The one, or perhaps two, exceptions known to the mating scheme above happen in L. hasselti, and in at least a sub-population of brown widows, L. geometricus. In L. hasselti, the male is much smaller than the female. On his final approach, the male chambers over the female’s abdomen, inserts his emboli into the female’s bursa, then somersaults forward. The female must apparently catch him by biting the tip of his abdomen, or he would fall off, and the mating wouldn’t be successful. According to one Australian worker, most males aren’t killed and eaten, but merely injured. The male staggers off to die a day or so later.

Using brown widows, a researcher in the US working with specimens collected in Florida, reported that the males were tightly wrapped with silk after the somersault, which would suggest he is later eaten by the female. The brown widow was found for the first time in Texas in 1996, and wanting to see this somersaulting behaviour, I mated a few virgin female brown widows collected from Texas. No somersaulting or wrapping was seen, and one male lived with the female in the same cage for nearly three months. He fed on crickets caught by the female and must have mated with the virgin female at least once, since five eggsacs, most fertile, were produced by the female before he died, probably of old age. This suggests that the Texas brown widows could be a different species, or a sub-population utilising different mating behaviour.

Prey, Predators & Parasites Of Latrodectus

Widow spiders will eat nearly everything they can overcome but insects make up the lion’s share of prey items. These include many flies, bees, wasps, ants, beetles, true bugs and pretty much anything else that can make its way into the web and attract the attention of the spider. Some prey species, which contain toxic defensive compounds, can kill a widow spider, examples being certain chafer beetles and probably some toxin-containing caterpillars. The list of insect prey species that L. mactans will eat is virtually unlimited in number and more could probably be found until the investigating researcher became bored or retired. An assortment of other arthropods, reptiles, mammals (mice) and other types of animals have been reported, or alleged, as being subdued and consumed by L. mactans.

Egg predators of widow spiders, often arbitrarily called parasites, are not uncommon. They include the larvae of certain flies, wasps and mantidflies (Mantispidae, a neuropteran). Suspected by some to be the most effective widow enemy of them all, egg predators can deny a tremendous number of individuals a chance at life. One of the two dominant mud dauber wasps in North America may specialise on widow spiders at times. The steel-blue mud dauber, Chalybion californicum (Saussure) has been found at times to prefer provisioning its mud cell with widow spiders over other spiders. Other predators of widow spiders include some birds, reptiles, and small mammals.

The Species

Southern Black Widow

The southern black widow, Latrodectus mactans (Fabricius) has been reported from the eastern half of the US: the Gulf states and from northern Florida north to southern New England, west to Kansas, and south through the eastern half of Texas and perhaps into Central and South America.

The southern black widow is largely black, although some may tend toward a brownish colour, especially under bright light. The females have a glossy black abdomen and legs which appear hairless, although inspection under microscope will reveal a dense matting of short hair. They almost always sport a fairly typical hourglass marking on the back, with another red mark, dot, series of dots, or stripe on the dorsal side of the abdomen.

Once mature, males don’t live long compared to the females. The average southern black widow male’s lifespan is probably between one and three months, with a small percentage living a few months longer. Females may live two years or so, with some individuals surviving three or more years.

The habitat preferences for southern black widows are usually in locations close to the ground. Height preference exceptions include under overpasses and bridges and in buildings and similar situations. In these cases, the webs may be far from the ground. Webs of adult females have been found under cow patties, under rocks, in out-buildings, warehouses and other structures, in below-ground water meter cubicles, lawn-watering-control housing, and pump houses, and in vegetation.

The web consists of an irregular mesh that may exceed two, three or more feet in length, probably depending upon the space available to the spider for construction. The web radiates out from a funnel-like retreat. The innermost retreat, where the spider is usually found, is often in a narrow, protecting indentation, either natural or man-made (a crevice in concrete or wood). The web is quite strong, having a bit less tensile strength than an equal diameter strand of steel.

The egg-sacs of L. mactans are grey and nearly spherical. A distinct nipple adorns the top. Egg counts may range from under 100 to over 1,000, depending upon many factors. The most important is probably nutritional status and the maturity percentage of the ovaries (all ovaries are not usually mature and producing eggs at the same time). The egg-sac diameter ranges from 10 to 13 mm. The texture of the egg-sacs of L. mactans is paper-like and nearly opaque. Infertile egg-sacs made by unmated females are often misshapen and translucent. Females will produce their first egg-sac about a month after mating (some take longer, others take much less time). Southern black widow females usually construct between five and ten egg-sacs during their lifetime, but as many as fifteen have been reported.

The eggs (embryos) hatch (eclosion) into postembryos in one to three weeks but remain within the egg-sac. Much of this variation depends on temperature, a measurement largely unreported by early workers. A day to a few days later, they moult (ecdysis) into one-inch in-stars, although they still remain within the egg-sac. The one-inch instar continues to derive nutrients from the yolk sac in its abdomen for some time before it begins feeding. Some species, or individuals within species, may not commence feeding until the second instar.

Females mature in the sixth to ninth instar and males mature earlier in the fourth to seventh, with most maturing in the fifth and sixth instar). Time to maturity varies greatly, largely depending on temperature and nutritional status. Males of the largest of the five North American species are almost always smaller than females, although some may have legs which are as long as those of the female. The males also have a thinner, more elongate abdomen.

Western Black Widow

The western black widow Latrodectus hesperus (Chamberlin & Ivie), is found roughly in the western half of the US, north to the Pacific coast of Canada, and in northern Mexico. Females have black abdomens and legs but, like L. mactans, some may be brownish in colour. Some may sport a spot or centre band on the dorsal abdomen. The hourglass marking on the back is normally present, and is often yellow in males, although it may be lacking in certain sub-populations.

Some colour variations are found in Texas and California (and probably northern Mexico) and these have red and white striping as juveniles, which some retain as adults. Females look so unlike widow spiders that only those familiar with the genus may suspect what they are. Western black widow females are larger on average than the other US widow species, but males are smaller than southern black widow males. Both sexes also live somewhat longer than does L. mactans.

Habitat, courtship and mating and other aspects of their lifestyle are similar to those of L. mactans. The egg-sacs of L. hesperus are pear-shaped and flat-edged at the top and, occasionally, the top of the egg-sac has a dull point. They are about 13 to 14 mm in height and 10 or 12 mm in diameter. The texture is tough and paper-like and the colour is a light tan or creamy yellow. Latrodectus hesperus produce more egg-sacs than L. mactans, with twenty-one being constructed by one female. Most females, however, probably average only a few more than L. mactans.

The time taken to reach maturity is thought to be several weeks longer than in L. mactans.

Northern Black Widow

The northern black widow Latrodectus variolus (Walckenaer) ranges from eastern Texas, east to northern Florida and north to south-eastern Canada. One popular book shows its range as being throughout the US and southernmost Canada, except for most of southern Florida and much of the south-western USA. Kaston (1970) argued that only L. hesperus is found west of about the middle of Texas, Oklahoma, and Kansas to the Canadian provinces, and could identify no L. variolus specimens from western areas indicated by the book. To my knowledge, the issue has not as yet been resolved.

The legs and cephalothorax of female L. variolus are black (with exceptions, as always). Red spots run down the midline of the dorsal abdomen. Three pairs of white stripes adorn each side of the abdomen, and many individuals have a thin white circle near the front of the dorsal abdomen. The hourglass pattern is incomplete, with a split in the middle forming what looks like two red triangles.

Habitat, courtship and mating, and other aspects are similar to that of L. mactans, with some exceptions. In the south-eastern portion of the range of L. variolus, they have been found far from the ground in the branches of trees. This has not been reported for populations elsewhere. The egg-sac of L. variolus is pear-shaped and usually flat-edged at the top, as with L. hesperus. L. variolus eggsacs are, however, light tan in colour, often with a hint of grey. The egg-sacs are about 13 to 14 mm in height and 10 or 12 mm in diameter. The texture is tough and paper-like.

The time required to reach maturity is thought to be some weeks longer than L. mactans.

Red Widow

The red widow, Latrodectus bishopi (Kaston), is so far found exclusively in south-eastern and central Florida. They are brightly coloured, with the carapace and legs of most specimens being bright orange. Other individuals may have yellow or red legs and cephalothorax. The hourglass marking is variable, and a complete hourglass is not common. Most have only the anterior triangle, and some have just a hint of a posterior triangle. The abdomen has red spots along the midline of the dorsum. White patches occur along the sides of the abdomen.

Little is known about the life-span or size of red widows relative to the other widow spiders, but their preferred habitat is distinctly different than those of other North American widow spiders. Webs are found three to four feet up, sometimes further, stretched between palmetto plants in dry, sandy pine scrub areas. The irregular mesh web resembles the sheet-like web of Linyphia (Linyphiidae, sheetweb weavers). Anecdotal reports claim individuals have occasionally been found in habitats more typical of the other widow spiders.

The egg-sacs are papery and light tan in colour. Information on time to maturity of the red widow also has not been investigated, or has not been published. Red widows are suspected of requiring a more humid environment than the other species. They may also have a shorter life-span.

Brown Widow

The brown widow, Latrodectus geometricus (C. L. Koch), has been termed a cosmotropical species (i.e. it is found in most, or all, tropical or semi-tropical areas), but is known to occur in the US only in Florida and extreme southern Texas. They probably now occur throughout the Gulf States of the US. The overall colour can vary from pale-yellow to black, but most are assorted shades of brown or grey. A complete hourglass is usually present.

Male brown widows may live two to four months, with some less, and others more. Females probably live more than a year, perhaps longer. The habitat of the brown widow is similar to that of L. mactans, except that they may take advantage of human structures more than the other species. In Florida, they are often found in higher numbers around lighted areas to which insects are attracted. The webs are similar to that of L. mactans.

Although serious Latrodectus bites are rare in any event, the venom of L. geometricus has been reported as three to four times less potent than that of Latrodectus indistinctus (O. P. Cambridge), an African species.

The highest number of egg-sacs reported as being produced by a brown widow female is twenty-nine, with a total of 5,761 eggs. The egg-sac made by the brown widow is totally unlike those of the other North American species. The egg-sac does not have a paper-like texture, is covered with spike-like protuberances, and is translucent. Most egg-sacs are near 10 mm in diameter, but egg-sac size is highly variable. The number of eggs in each sac is also highly variable.

Males may mature in a month or less after emergence from the egg-sac and most mature within two or three months. Females take longer to mature. Temperature will speed up development (if elevated), or slow it down (if kept cooler) by significant time periods.

Bite Treatment

Most widow bites do not require treatment, but authorities advise people to at least visit their doctor if bitten. The bite of a widow spider can kill, depending on the amount of venom and the sensitivity of the person affected. The venom contains fast-acting neurotoxins (nerve poisons) that usually dissipate in one to three days. A widow bite (uncommon in the US) can be painful, but a quick trip to your physician or emergency room can generally fix it. Fatalities usually only occur in the very young, very old, or in those with pre-existing health problems usually associated with damaged immune systems.

Physicians may administer calcium gluconate, or a similar drug, which rids the patient of the painful symptoms. Some physicians prefer to administer only calcium gluconate and pain killers and try to ride out the progression of the neurotoxin. If this is not possible, an injection of Latrodectus spp. antivenin can be used successfully, although most physicians are very reluctant to use it.

In some relatively recent data reported from Poison Control Centers, between 1989 and 1993, 2,404 bites, allegedly from widow spiders, were reported. Of this those who chose to report the seriousness of the outcome of the bites, 305 had no symptoms, 1,140 were considered minor, 272 were considered moderate, and 9 were considered major. No fatalities were reported.

Realistically, there are only two ways to be bitten by the extremely non-aggressive widow spider. A person can trick the spider into thinking their finger is prey by gently shaking the web, imitating an insect, or kill or severely injure the spider while the skin is in contact with the fangs. Bites happen, but not nearly as often as falsely reported as even jumping spiders look like widow spiders to some. Widow spiders are also very beneficial, along with other spiders, in agriculture and in gardens. Although I certainly don’t advise it, I’ve handled hundreds of widow spider individuals with my bare hands over the last two and a half decades and never had a problem.

Respect them, certainly, but don’t fear them, choose to admire their integral beauty instead.

Dr. Breene is an arachnologist and an entomologist, receiving his B.S., masters and Ph.D. from Texas A&M in College Station, Texas. He is editor of the American Tarantula Society, Chair of the Committee on Common Names of Arachnids of the American Arachnological Society, and a faculty member of the College of the Southwest in Carlsbad, New Mexico.

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