Spider-man’s spider webbing talent isn’t what you think it is. Sure, male spiders do have special appendages on the front of their bodies–they are really noticeable ”boxing gloves.” They actually can be up to 20% of a male spider’s body weight.
Those are not, however, what spiders shoot silk or webbing out of. These pedipalps have one function. SEX.
That white, sticky stuff Peter Parker is shooting out of his wrist? Um. Yeah.
More details than you actually want to know at Bug Girl's Blog.