Corrected entry: When salt extracts the venom from a black widow spider, you see the underpart of the spider. If you look closely, there is nothing on its bottom. Black widows have a red hourglass-shaped mark on their bottom to show that they are female. Males -such as the one in the movie- do not contain the potentially deadly neurotoxin that the female does.
movieepicfailiure
26th Aug 2010
Correction: There is nothing in the movie to suggest that the spider is a Black Widow. It is a different kind of spider, one that Mike discovered in North Korea (as shown in the Extended Cut). The spider was named after Beatle Pete Best. It also makes more sense - for her purpose, Salt would not want to use a spider venom that could be potentially deadly given the wrong dose (like the Black Widow), but one with a less harmful venom.
Twotall