Sampling Spider Webs for the Detection of Black Widow DNATo extract DNA from a spider or examine its genitals, not only does the spider have to be found and captured, but it often must then be killed, potentially damaging the ecosystem one is attempting to study. Collecting spider webs is considerably less difficult than collecting the spiders themselves, as the webs don’t move and many species build new webs each night, abandoning the web every morning.