They do not call the black and brown widow spiders (Latrodectus species) “widows” without good reason. It is a rare male of these species that survives the mating act. In fact, some females are so eager to consume rather than consummate that they eat the male before he is through with his prenuptual display. This does not hold true for all spiders, but cannibalizing the male is common for members of the Argiope tribe.
Male Escape Strategies
Although the specifics differ, mating in all species follows a pattern similar to that displayed by the half-inch long venusta spider (Leucauge venusta).
- Approach - The male moves onto the female's web at the same height as the female. Upon entering the web, he begins strumming on the radial spokes, plucking them with his second pair of legs. He moves toward the female, usually in the center of her orb, while continuing to pluck the spokes.
- Contact – As he nears the female, the male raises his second pair of legs and begins to wave his pedipalps from side to side.
- Sperm Transfer – As the female quickly moves toward him, he grasps her raised legs with his legs, and moves slowly underneath her – directly under the "umbrella" of her fangs and legs. He reaches back with a front leg, collects a spermatophore (wrapped package of sperm) from his genital opening, and places it into the female's genital opening.
- Danger – From contact to transfer, the male is at the most risk. All the female has to do is to slip from his grasp, drop onto him, and sink her fangs into his body. The male venusta spider. although only about 1/10th to 1/3rd her size, is able to hold the female away until he can back out from under her. Males of other species are not always as lucky.
- Escape – Moving out from under the female, the male runs directly upwards until he is off the web and stops several inches above it.
- Repeat – After a short while, the male moves around the web until he is again at the same location he began the process. Strumming the web, he again moves toward his chosen mate to repeat the process. In this species, the male may provide the same female upwards of eight spermatophores before leaving.
Benefit To The Female
Eggs are composed primarily of protein and fat. The usual prey of spiders are sometimes as little as 1% of the female's size. Small prey mean the female must wait to mate until she has stored enough nutrients to provide for her eggs.
- If she has not fed well, the appearance of a prey item (male) that is between 10% and 30% of her size might be too good an opportunity to pass up, so she eats the male before he can transfer sperm.
- If she has captured prey recently, she might let the male copulate and then eat him.
- A fully sated female would release the male to search for another female to mate with after he satisfies her reproductive needs.
Benefit To The Male
Male spiders mate near the natural end of their lives. Once they have culminated their reproductive requirement and passed on their genes. they have little purpose left. They could mate again, but often have become exhausted by their first session and die before making another effort.
- If the male provides a meal for his mate after mating with her, she converts the nutrients in his body into more and larger eggs. Larger eggs produce larger offspring. Thus, by feeding his mate, he is ensuring:
- His children obtain his genes.
- He fathers more offspring.
- His offspring are better prepared to make their way in the world from the day they hatch.
- The nutrients in his body are directly transferred to his children and do not provide sustenance to a scavenger or predator, allowing them to produce more of their offspring.
- If a male is eaten by a female of the species before he mates, the benefits to his offspring are not as direct, but he still enhances their survival.
- He does not provide genes to the next generation.
- His nutrients are used to increase the number and size of her offspring. Thus, he is helping to increase the number and fitness of baby spiders in the following year even if he does not pass on his genes.
- His nutrients are not being used to promote another species' fitness.
In a sense, the male that is eaten to provide for his offspring causes them to commit an indirect form of patricide (killing their father). Some species of spiders go even beyond this mode of altruism.
Female spiders usually die shortly after laying their eggs. In a group called the matricidal spiders in the genus Diaea, mother spiders do not die after producing egg sacs. Rather, they stay with their egg sacs until the spiderlings hatch out. At this time, the mother spider flips onto her back and allows the babies to clambor over her, biting and injecting their venom into her body. She dies. After her body tissues have become digested, her young feed on her, molt, and disperse with their mother's body providing the energy to travel.
Brown Widow, Phoenix, AZ
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The Male's Mating Umbrella
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Venusta Spider Eating
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