Just in case you aren't "in the loop" -- the concept of Dried Frog Pills comes from Terry Pratchett's Discworld novels.
Dried Frog Pills are an hallucinogen that's used by the Bursar of Unseen University. The pills are carefully designed to make him hallucinate that he is sane -- and you cannot argue with logic like that :-)
@antedeluvian: I seem to remeber someone making the apt suggestion of a shiver of sharks. In my case would work for snakes as well.
A "shiver of sharks" is an "official" one -- they don't use that for snakes although I agree it would be apt (as would a "scream of spiders"). You can have a "knot of snakes" and a "rhumba of rattlesnakes".