National Geographic : 1991 Sep
Spider procreation requires exact ori entation and fit of puzzle-like parts. The two male palps (right) first collect sperm from an abdominal open ing. Each palp has two keys. One (tibial apophysis) fits securely into a notch in the female's abdomen. The other (embolus, at the end of the tegulum) moves into the female organ (epigynum) to deliver sperm, as balloon-like mem branes (hemato dochae) inflate. ILLUSTRATIONBY GREGHARLIN, SRW INC.