Spiders copulate or reproduce in a very unusual way.
They have evolved the nicety of internal fertilization, but since the males don’t have a penis, they use their pedipalps, the arm-like “feelers” adjacent to the mouth, to place their sperm into the body of the female.
The tip of the pedipalp, which works like a rubber-bulb syringe, is the intromittent organ.
Before a male seeks out a female, he sucks his pedipalps full of semen that he has deposited from the true genital opening at the base of his abdomen onto a small silken web that he has spun ahead of time.
If he survives the courtship, he thrusts a pedipalp into one of the female’s two genital openings and squirts in his semen.