''Latrodectus mactans'', known as southern black widow or simply black widow, and the shoe-button spider, is a venomous species of spider in the genus ''
Latrodectus
''Latrodectus'' is a broadly distributed genus of spiders with several species that are commonly known as the true widows. This group is composed of those often loosely called black widow spiders, brown widow spiders, and similar spiders. Howeve ...
''. The females are well known for their distinctive black and red coloring and for the fact that they will occasionally eat their mates after reproduction. The species is native to
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. The venom can cause pain and other symptoms, but is rarely fatal to healthy humans.
Taxonomy
''Latrodectus mactans'' was first described by
Johan Christian Fabricius
Johan Christian Fabricius (7 January 1745 – 3 March 1808) was a Danish zoologist, specialising in "Insecta", which at that time included all arthropods: insects, arachnids, crustaceans and others. He was a student of Carl Linnaeus, and is cons ...
in 1775, placing it in the genus ''
Aranea''.
[ It was transferred to the genus ''Latrodectus'' in 1837 by Charles Walckenaer and is currently placed in the family ]Theridiidae
Theridiidae, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, is a large family of Araneomorphae, araneomorph spiders first described by Carl Jakob Sundevall in 1833. This diverse, globally distributed family includes ...
of the order Araneae
Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species dive ...
.[ The species is closely related to '']Latrodectus hesperus
''Latrodectus hesperus'', the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-sha ...
'' (western black widow) and ''Latrodectus variolus
''Latrodectus variolus'', the northern black widow spider or northern widow, is a venomous species of spider in the genus ''Latrodectus'' of the family Theridiidae. The population is closely related to the southern black widow, ''Latrodectus mact ...
'' (northern black widow). Members of the three species are often confused with the genus '' Steatoda'', the false widows. Prior to 1970, when the current taxonomic divisions for North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
n black widows were set forth by Kaston, all three varieties were classified as a single species, ''L. mactans''. As a result, there exist numerous references which claim that "black widow" (without any geographic modifier) applies to ''L. mactans'' alone. Common usage of the term "black widow" makes no distinction between the three species.
Description
The body length (excluding legs) of the mature female is , and for males. Legs are long in proportion to body. Females are shiny and black in color, with a red marking in the shape of an hourglass on the ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...
(under) side of her very rounded abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
. There is much variation in female size, particularly in egg-carrying (gravid) females. The abdomen of a gravid female can be more than in diameter. Many female widows also have an orange or red patch just above the spinnerets on the top of the abdomen. Juveniles have a distinctly different appearance from the adults; the abdomen is grayish to black with white stripes running across it and is spotted with yellow and orange. Males are either purple, or closer to the appearance of the juveniles in color.
The web of the black widow spider is a three-dimensional tangled cobweb of exceptionally strong silk.
Range
The southern widow is primarily found in (and is indigenous to) the southeastern United States
The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...
, ranging as far north as Ohio
Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
and as far west as Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
. The northern black widow ''(L. variolus)'' is found primarily in the northeastern United States
The Northeastern United States, also referred to as the Northeast, the East Coast, or the American Northeast, is a geographic region of the United States. It is located on the Atlantic coast of North America, with Canada to its north, the Southe ...
, though its range overlaps with that of ''L. mactans''. In the Dominican Republic
The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean region. It occupies the eastern five-eighths of the island, which it shares wit ...
''L. mactans'' is found throughout the whole country. ''L. mactans'' is also found throughout Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
where its range overlaps with that of ''Latrodectus hesperus
''Latrodectus hesperus'', the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-sha ...
'' and ''Latrodectus geometricus
''Latrodectus geometricus'', commonly known as the brown widow, brown button spider, grey widow, brown black widow, house button spider or geometric button spider, is one of the widow spiders in the genus ''Latrodectus''. As such, it is a 'cousi ...
''.
''L. mactans'', along with ''L. hesperus'' and ''L. geometricus'', is established in the Hawaiian Islands
The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...
(USA). One pathway of entry into Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
for at least one of these black widow species is imported produce (which is also considered an important potential pathway for widow spiders elsewhere).
Reproduction
When a male is mature, he spins a sperm web, deposits semen on it, and charges his palpal bulb
The two palpal bulbs – also known as palpal organs and genital bulbs – are the copulatory organs of a male spider. They are borne on the last segment of the pedipalps (the front "limbs" of a spider), giving the spider an appearance often descr ...
s with the sperm. Black widow spiders reproduce sexually when the male inserts his palpal bulbs into the female's spermathecal openings. The female deposits her eggs in a globular silken container in which they remain camouflaged and guarded. A female black widow spider can produce four to nine egg sacs in one summer, each containing about 100–400 eggs. Usually, eggs incubate for twenty to thirty days. It is rare for more than a hundred to survive this process. On average, thirty will survive through the first molting
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
due to cannibalism
Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...
, lack of food, and/or lack of proper shelter. It takes two to four months for black widow spiders to mature enough to breed; however, full maturation typically takes six to nine months. The females can live for up to three years, while a male's lifespan is about three to four months. The female may eat the male after mating.
Prey
Black widow spiders typically prey on a variety of insects, with a preference for fire ants if extant, but they also feed on woodlice
A woodlouse (plural woodlice) is an isopod crustacean from the polyphyleticThe current consensus is that Oniscidea is actually triphyletic suborder Oniscidea within the order Isopoda. They get their name from often being found in old wood. ...
, diplopods
Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a re ...
, and chilopods
Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
when they are young, and occasionally other arachnids
Arachnida () is a Class (biology), class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, opiliones, harvestmen, Solifugae, came ...
. The spider's web is even strong enough to catch animals as large as mice. When the prey is entangled by the web, ''Latrodectus mactans'' quickly comes out of its retreat, wraps the prey securely in its strong web, then bites and envenoms its prey. The venom takes about ten minutes to take effect; in the meantime, the prey is held tightly by the spider. When movements of the prey cease, digestive enzymes are released into the wound. The black widow spider then carries its prey back to its retreat before feeding.
Natural enemies
There are various parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s and predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s of widow spiders in North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, though apparently none of these have ever been evaluated in terms of augmentation programs for improved biocontrol
Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
. Parasites of the egg sacs include the flightless scelionid wasp ''Baeus latrodecti'', and members of the chloropid fly genus '' Pseudogaurax''. Predators of the adult spiders include wasps, most notably the blue mud dauber '' Chalybion californicum'', and the spider wasp
Wasps in the family Pompilidae are commonly called spider wasps, spider-hunting wasps, or pompilid wasps. The family is cosmopolitan, with some 5,000 species in six subfamilies. Nearly all species are solitary (with the exception of some group-ne ...
''Tastiotenia festiva
''Tastiotenia festiva'' is a species of spider wasp in the subfamily Pompilinae. It was first described by its discoverer, Howard Ensign Evans, in 1950. It is a rather small spider wasp species, growing from 3–6.5 mm in length and has onl ...
''. Other species including Mantis
Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They ha ...
or Centipede
Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
also will occasionally and opportunistically take widows as prey, but the preceding all exhibit some significant specific preference for ''Latrodectus
''Latrodectus'' is a broadly distributed genus of spiders with several species that are commonly known as the true widows. This group is composed of those often loosely called black widow spiders, brown widow spiders, and similar spiders. Howeve ...
''.
Furthermore, in 2012, researchers published a paper suggesting that the black widow's close relative, the brown widow
''Latrodectus geometricus'', commonly known as the brown widow, brown button spider, grey widow, brown black widow, house button spider or geometric button spider, is one of the widow spiders in the genus ''Latrodectus''. As such, it is a 'cous ...
, may be competing for territory with, and ultimately displacing black widows in Southern California.
Toxicology
Although the reputation of these spiders is notorious and their venom does affect humans, only mature females are capable of envenomation in humans; their chelicerae
The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as "jaws", chelicerae may be shaped as either articulated fangs, or similarly ...
—the hollow, needle-like mouthparts that inject venom—are approximately 1 mm, or .04 in. in length, making them long enough to inject venom into humans, unlike those of the much smaller males. The actual amount injected, even by a mature female, is variable. The venom injected by the female black widow is known as alpha-latrotoxin
A latrotoxin is a high-molecular mass neurotoxin found in the venom of spiders of the genus ''Latrodectus'' (widow spiders) as well as at least one species of another genus in the same family, '' Steatoda nobilis''. Latrotoxins are the main acti ...
which binds to receptors at the neuromuscular motor end plate of both sympathetic and parasympathetic nerves, resulting in increased synaptic concentration of catecholamines. The symptoms are caused by lymphatic absorption and vascular dissemination of the neurotoxin. The symptoms that result from a black widow spider bite are collectively known as ''latrodectism
Latrodectism () is the illness caused by the bite of ''Latrodectus'' spiders (the black widow spider and related species). Pain, muscle rigidity, vomiting, and sweating are the symptoms of latrodectism.
There are several spider species all named ...
''. Deaths in healthy adults from ''Latrodectus'' bites are exceedingly rare, with no deaths despite two thousand bites yearly, and studies within the past several decades have been unable to confirm any fatalities from this or any of the other U.S. species of ''Latrodectus'' (e.g. zero fatalities among 23,409 documented ''Latrodectus'' bites from 2000 through 2008). On the other hand, the geographical range of the widow spiders is vast. Epidemics of mostly European widow spider bites had been recorded from 1850 to 1950, and during that period deaths were reported from 2 per 1000 bites to 50 per 1000 bites. Deaths from the western black widow
''Latrodectus hesperus'', the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-sha ...
had been reported as 50 per 1000 bites in the 1920s. At that same time, antivenom
Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...
was introduced. The LD-50
In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is th ...
of ''L. mactans'' venom has been measured in mice as 1.39 mg/kg, and separately as 1.30 mg/kg (with a confidence interval of 1.20–2.70). In 1933, Allan Blair
Allan Walker Blair (1900–1948) was a professor at the University of Alabama's medical school who is best known for allowing himself to be bitten by a black widow spider in order to investigate the toxicity of its venom in humans. As a result of t ...
allowed himself to be bitten by the spider in order to investigate the toxicity of its venom in humans and as a means of convincing skeptics at the time who thought that the spider's venom might not be dangerous to humans.
There are a number of active components in the venom:
* Latrotoxin
A latrotoxin is a high-molecular mass neurotoxin found in the venom of spiders of the genus ''Latrodectus'' (widow spiders) as well as at least one species of another genus in the same family, '' Steatoda nobilis''. Latrotoxins are the main activ ...
s
* A number of smaller polypeptides
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
A p ...
—toxins interacting with cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
channels, which can affect the functioning of calcium, sodium, or potassium channels.
* Adenosine
Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...
* Guanosine
Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose ( ribofuranose) ring via a β-N9- glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate ...
* Inosine
Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a β-N9- glycosidic bond. It was discovered in 1965 in analysis of RNA transferase.
Inosine is commonly found in tRNAs and is ...
* 2,4,6-trihydroxypurine
The venom is neurotoxic
Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...
.
References
External links
Fact Sheet on the Black Widow Spider
includes information on habits, habitat and threats
on the UF / IFAS Featured Creatures website.
{{DEFAULTSORT:Latrodectus Mactans
mactans
Spiders of North America
Fauna of the Caribbean
Arthropods of the Dominican Republic
Fauna of the California chaparral and woodlands
Fauna of the Southeastern United States
Fauna of the Western United States
Spiders described in 1775
Taxa named by Johan Christian Fabricius