It appears that they covered it with glue, so that they could count the insects at the end of the day. While this does definitely raise some questions, it also

It appears that they covered it with glue, so that they could count the insects at the end of the day. While this does definitely raise some questions, it also made the initial test probably quick and easy; no human test subjects needing to sign a waiver that they were willing to hang out covered in glue all day. Kind of like testing things on lab rats first. Definitely would need to be tested in some other way, though. Lots of things that work on lab rats don't work on humans.