The number of maxillary palpal joints usually is five but varies between two and six. |
The male palpi are long, with large tarsi and palpal organs and a long hook on the outer side of the tarsus. |
The sperm is then absorbed with the palpal organ, where it is stored until mating. |
In x-notata the palpus is as long as the cephalothorax, and the tarsus and palpal organ small and round. |
The palpal organs and male palpi are of great variety and distinguish the males of all species without much difficulty. |
And if you're more interested in how arachnids do it with palpal specializations than molluscan harpoons, I've got an article on how spiders mate. |