A spider’s web ensnares its prey for far longer than it takes the spider to down its next meal, a new study finds. Spider webs bear traces of DNA from whatever creatures have come in contact with them, according to the research led by University of Notre Dame biologists and published in PLOS ONE.

The scientists used black widow spiders from Indiana’s Potawatomi Zoo. After they built webs, the four spiders were fed crickets dropped into their webs. The researchers then took samples of the webs, and extracted DNA from them. They were able to identify the species of both spider and their prey from these web samples—even one from a spider that had died and been removed from its exhibit (along with its prey) almost 90 days before.

While the presence of little bits of spider DNA may make their webs seem a little creepier, it could be a boon for keeping track of spider and insect populations. Spiders tend to be elusive, but their webs are easier to track down, so researchers could use this genetic material to monitor spider biodiversity, even after the arachnids themselves have died or moved on from that habitat. DNA testing could also reveal information about what type of insects get caught in the webs.

However, this study tested webs housed indoors, and outdoor spider webs may deteriorate more rapidly, so the results might not be as clean-cut. 

[h/t Gizmodo]