Latrodectus sp. is an amazing species with mating habits that may seem very surprising to some, but are just part of the normal life history of the Black Widow Spider. As for the precursor courting of the spiders before reproduction, it has been found that both the females and males secrete certain pheromones to attract the opposite sex. In the Journal of Arachnology in an article by Ross, K., & Smith, R. L. it is described how these sexually specific pheromones are incorporated into the silk the Latrodectus sp. produce when weaving their webs. Male spiders becoming sexually aroused when they first come into contact with the females web due to the pheromones in her silk. The male spider is able to pick up the scent of the female after it molts and fills its palpal organs with semen and abandons its web and begins to hunt for a mate. The male enters the web of the female, sensing her pheromones with chemoreceptor hairs on his legs, and begins to move about the web.

The chemoreceptor cells are located on the distal ends of all appendages and are open structures that contact the web during the courtship process. In this process it was discovered that not only do the males sense the webs, but only respond sexually to female webs indicating that they can tell the difference between male and female pheromones. Different species of Latrodectus sp. were tested to check if the males of one species would respond to the female chemicals of another species and across the board it was proven that the males had the same sexual reaction. The males could however tell the difference between different genus’ of Theridiidae which keeps them from the possible danger of wandering into a predators web and becoming stuck. The pheromones of the females silk are so strong that the male Black Widow Spider would still get the same arousal by smelling a female’s deserted web after 50 days of the females' absence. However, one problem that arises from the males hypersensitive chemoreceptors is that they can waste time and energy trying to mate with female spiders that are not yet sexually mature and therefore the male may miss the opportunity to pass on his genes. Some males were observed to wait it out on the web of an immature female until she became of reproductive age and the male had the easiest way of fertilizing her eggs.

The male spider then makes strategic cuts on the web of the female to reduce her chance of escaping. The male Black Widow Spider begins to make vibrations with his body and leaves a trail of silk behind him as he navigates the web and picks up on the female’s pheromones. Both the males and females exhibit very jerky, violent movements from their abdomens before copulation. These vibrations function in the announcement of the male on the female’s web and the female being able to recognize the male as a potential mate rather than a dangerous predator or unsuspecting prey. Finally the male climbs onto the female and penetrates her with his palpal embolus.

The Black Widow Spider reproduces sexually when the male spider inseminates a female and fertilizes her egg sac by inserting his embolus, with an apical sclerite at the tip, into the bursa of the female. Almost always during this copulation the male’s apical sclerite breaks off at the tip; the male’s palpal organ is one that after the first copulation it may not return to its original position. The broken off tip of the embolus can stay within the genitalia of the female preventing her from mating again. Up until 1985, it was believed that after the apical sclerite broke off the male would no longer be able to copulate again and would die soon afterwards. This was however disproved in a series of experiments conducted by The Department of Entomology and Department of Biology at Texas A&M University where they found that a male spider could mate with up to three different virgin female spiders. Although the apical sclerite’s of the males were still broken off within the first copulation it was shown that the males could still reproduce with the damaged embolus. In the Australian Journal of Zoology it's described how the actual act of copulation between a male and female spider involves a somersault action by the male. After the male penetrates the female with his papal embolus he does a 180 degree turn so that his abdomen is resting against the mouth of the female in which most cases she then begins to devour him. Further information about the study of the multiple partners of a male Black Widow Spider can be found here.

There is another stipulation with the amount of times a male can mate which is whether or not the female is hungry after copulation or whether the male can escape. This is called sexual cannibalism in which the female Black Widow Spider feeds on the male spider after they reproduce together.  The main reason that sexual cannibalism occurs is because it can be beneficial to the fitness of the male spider, unless the male could mate more than four times in his lifetime. The nutritional value that the eaten male provides to the female increases his fitness in the way that the female is healthier and more likely to lay viable eggs that will hatch and add to the Black Widow Spider population. In some species of Latrodectus the male spider will hang around the female’s web for a few days after sexual intercourse until he is eventually digested. It is unclear, however, how often sexual cannibalism takes place within the black widow spider population. More can be found on the sexual cannibalism of Latrodectus sp. here.

Figure 1. Female with male just before insertion of the pedipalp into the epigyne.