scramblers

http://www.totalvac.com/parts/EX900-A-TP1.html?zmam=6843742&zmas=1&zmac=7&zmap=EX900-A-TP1 My friend picked up a few of these to fend off spiders, but I can't for the life of me see how it could actually work. How does it scramble spider, roach and rat brains, but not a dog or a cat? It seems...