Latrodectus It is a genus of spiders of the Theridiidae family that comprises 31 species worldwide and that are commonly called black widows. They are characterized, among other aspects, by presenting a marked sexual dimorphism with females much larger than males, clearly separated lateral eyes and chelicerae without teeth..
The species of the genus Latrodectus they are insectivorous and can practice cannibalism. Its venom is extremely toxic to humans and its bite produces a syndrome called latrodectism, whose symptoms include psychomotor agitation, profuse sweating, spasms and stiffness of the thoracoabdominal muscles, as well as tachycardia..
They are dioecious, internally fertilized, oviparous organisms. After fertilization, the female can devour the male, however this behavior is more frequent in laboratory conditions than in natural environments. The female can lay up to 500 eggs in a unique protective structure called the ootheca..
Besides black widows, these spiders go by other names like bloody spiders or wheat spiders. Among the representative species of the genus are L. geometricus, which is the one with the widest distribution worldwide and L. mactans, the largest of the genus and the most common species of black spiders on the American continent.
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Spiders of the genus Latrodectus they are relatively large in size, with the females being larger than the males. Their lateral eyes are clearly separated and the first pair of appendages or chelicerae lacks teeth..
The abdomen is well developed and is globular or subglobular in shape. They have a structure called colulus of proportionally large size, this structure is located in the back of the abdomen or opisthosoma, instead of the cribelle (organ that produces a silk similar to wool and is called cribel silk).
Between the two pairs of lungs of the female is an oval transverse plate, with a simple and elliptical opening in the center, while the vulva has a pair of spermathecae connected with spiral copulation tubes to receive the male copulation organ that also spiral shape.
These spiders are generally black in color with bright, striking colored spot and band patterns, which serves as a warning to potential predators, known as aposematic coloration..
Black widows are chelicerate arthropods of the class Arachnida, order Araneae, family Theridiidae. The gender Latrodectus it was erected by Walckenaer in 1805, but the designation of the type species was made by Latreille in 1810.
This last researcher selected a species previously described by Rossi in 1790 as Aranea tredecimguttata, as a type species for the genus Latrodectus. The type locality for this species is the Tuscany region of Italy.
To date, more than a hundred species of this genus have been described, however, currently only 31 species are recognized as valid, while the rest have been assimilated to the valid species of this or other genera of spiders..
Black widows are basically insectivorous spiders, although they can also feed on other arthropods, including spiders of the same species. This cannibalism occurs especially in the female, who can devour the male after copulation..
Spiders capture their prey using their spider webs. When a prey falls into the web, the spider approaches and covers it with a spider web with the help of its hind legs. When the prey is immobilized, it injects its poison and then the digestive juices.
Digestion is extracellular and occurs in the prey's own body. Once the tissues of the prey have been digested, the spider proceeds to absorb the digested material.
Spiders of the genus Latrodectus they are of sexual reproduction and dioecious, that is to say, they present / display separate sexes. Females and males differ in size (sexual dimorphism), with females being larger than males..
Fertilization is internal and the females are oviparous. After copulation and fertilization of the female by the male, the female can devour it, a behavior that has been observed in many of the species of the genus..
The females will deposit up to 500 eggs in a waterproof envelope called the ootheca. The eggs will develop inside this structure and when they hatch, small spiders will emerge similar to adults, that is, they present direct development..
The venom of black widows is a yellowish fluid made up of different lipids, carbohydrates and proteins, and whose main active component is α-latrotoxin. It has a presynaptic neurotoxic action that induces the massive release of acetylcholine, catecholamines and other neurotransmitter substances at the level of the neuromuscular plate..
Latrotoxins are a group of high molecular weight, acidic pH proteins found in widow spider venom. There are several types, whose toxicity is selective depending on the prey of the spiders. Latroinsectotoxins to, b Y d act on insects, α-latrotoxin on vertebrates and alatrocrustotoxin on crustaceans.
Both males and females produce the poison, but the greatest danger to humans is represented by female spiders, since they are larger and therefore their fangs are large and strong enough to be able to effectively attack the human being and inject the poison..
The syndrome produced by embattled by black widows is called latrodectismo. It can be confused with various pathologies, such as acute appendicitis, acute abdomen, biliary or renal colic, pancreatitis, tetanus, acute myocardial infarction, strychnine poisoning and pre-eclampsia in pregnant women..
The first symptoms appear several minutes after the bite and consist of local pain and erythema. The pains intensify over time, then the feeling of burning or stinging in the feet appears, cramps, muscle spasms, stiffness of the abdominal wall, nausea, vomiting, anxiety, priapism, headaches, among others..
Complications from widow spider poisoning are rare, but can even lead to death, something that only occurs in just under 5% of poisoned patients. There is an effective antidote against poisoning developed by the Biotechnology Institute of UNAM in Morelos and which has been approved for use in humans in several countries..
This spider is about 15mm in length. It is a cosmopolitan species that scientists believe originally from South Africa, but currently inhabits the warm areas of the American continent, Africa, Asia and Australia.
The brown widow adapts very well to living with humans and can make its fabric in different objects such as bicycle parts, car engines, under furniture or on windows and doors, among others..
The coloration of the organisms of this species is generally grayish, with a characteristic spot that has the shape of an hourglass, located on the ventral surface of the abdomen, being in this species normally orange or yellow. The legs have alternating bands of light and dark colors.
The female lays more than 100 eggs in an ootheca characterized by spine-like structures. A female can lay more than one ootheca per breeding season.
Latrodectus geometricus It feeds on bees, crickets, grasshoppers, cockroaches and any other insect it manages to catch in its nets.
The female of the American black widow can reach 50 mm with the legs extended, which makes it the largest species of the genus. Its color is glossy black, with a red hourglass-shaped spot and legs that have brown and black bands..
It is an American species, with greater abundance in North America, but which is distributed as far as Argentina. Generally builds your fabric in dark, sheltered places, close to the ground.
It feeds mainly on insects although it can also feed on other arachnids. It is a peaceful spider and has no instinct to attack humans, it only attacks when threatened.
Also known as a bloody spider. It is a relatively small species. The female only reaches up to 15 mm and the male half that size. It has a characteristic color pattern, with 13 red spots surrounded by white, on the black abdomen..
It is a Mediterranean species, ranging from Spain and Portugal to Central Asia. Its main habitat is among the bark of trees, although it is also frequently found under stones.
The main prey that is part of its diet are grasshoppers, which it captures with the help of its cobweb that it builds in the form of a hood. It can also feed on other insects.
It is native to Australia, currently introduced in Asia. The female reaches 10 mm, but the male does not exceed 4 mm in length. The female is shiny black with a red band on the posterior dorsal part of the abdomen..
It is not an aggressive species, however in Australia, poisonings by this species are not rare, which generally occur when female spiders attack the male genitalia of human beings. The reason for attacking such an area is because these spiders tend to hide in latrines.
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