"Because it's not just the weird sex lives of spiders. This might be telling us something in general about how the world works."

 That's especially true if the black widows are sexed-up cannibal females.  

BBC

Many widows are cannibalistic; a redback male will often catapult himself into the female's mouth during copulation. This extreme sexual sacrifice will ensure at least some of his sperm makes it through the door.
"Because the males have two copulatory organs, he inseminates each organ in two separate copulations." The redbacks will approach the female once, she'll start to eat him, then he gets off, courts her again, and goes back a second time—to finish (and be finished off). "If you don't court long enough, she will kill you after one mating. And then she's more likely to mate with a rival."

To summarize the history of Russia in three words: It got worse.

Traumatic insemination – male spider pierces female’s underside with needle-sharp penis

The courtship rituals of the spider Harpactea sadistica start innocently enough, with a dance and a hug. The male spider taps the female gently with his front legs and embraces her. But from that point onwards, things for the female go rapidly downhill. The male bites her and she becomes passive, allowing him to manoeuvre her into position. Like all spiders, his genitals are found next to his head, on a pair of appendages called the pedipalps. But unusually, his penis [es] end in a needle-sharp tip called an embolus. 
The male hooks [a loop from one of his penises] around the opposite embolus to steady it. Then, by rotating the anchored needle, he drives the point straight through the female’s underside and ejaculates directly into her body cavity. On average, he does this six times, moving slowly downwards and alternating between his two penises. The entire cringeworthy sequence lasts about 15 minutes and throughout it, the male spider never penetrates the female’s actual genital opening. 

When most [bugs] mate, the male ejects sperm into the female’s vulva, and she stores it in a special pouch called the spermatheca. These pouches allow females to control when she fertilises her eggs, by voluntarily shunting sperm onto them before she lays. It also means that the last male to mate with her typically sires most of her offspring, because his sperm flushes out those of earlier liaisons. 

Science

This system means that there’s a fever-pitched sperm competition between males. Different species have evolved bizarre adaptations to get an edge in these conflicts. Some guard their mates after sex. Others leave behind “mate plugs” – chastity belts that block the female’s genitals. The males of one species take this to an extreme, by spontaneously dying during intercourse and turning their entire bodies into a mating plug.

But H.sadistica‘s brutal sexual practice allows it to bypass the competition altogether because the male’s sperm can travel directly to the female’s ovaries through her bloodstream. By wresting control of fertilisation from females, males ensure that when they mate, their sperm isn’t shunted aside at the risk of later removal.  

  H.sadistica practices a style of sex that’s understandably known as “traumatic insemination“. It’s disturbingly common among insects and other invertebrates, and is most famously practiced by bedbugs.

 Quoting Isabella Rossellini in io9

  "The bed bug, Cimex lectularius, has a unique mode of copulation termed "traumatic" insemination during which the male pierces the female's abdominal wall with his external genitalia and inseminates into her body cavity."

We conclude that traumatic insemination is probably a coercive male copulatory strategy that results in a sexual conflict of interests."

The male bed bug bypasses a perfectly good set of genitals, choosing instead to stab his lady in the belly with his dagger penis.

the male of a species evolves features that increase its chances of breeding, but at the female’s expense. The reverse may also happen. Their partners coevolve strategies to either fend off unwanted advances or to protect themselves from physical harm

 Not trying to stretch a metaphor here, but the man-woman-thing is never pretty.