There are reams of information in The US Patents Dept all online: a snippet...
For those budding 'fly-catchers wherever they may be..
"As a generality it can be said that the fly attractants known to the prior art are formulated to attract either the house fly or the blow fly, but none are known to have substantial utility in attracting both of them. One of the reasons that the attractants known in the prior art are specific to one or the other of these two species of flies is that the blow fly and the house fly do not eat the same kind of food. The blow fly, for one, thrives on decaying meats including red meats, chicken and fish. House flies, on the other hand, subsist mainly on rotten vegetables and animal feces. Because of these natural predispositions, blow flies are more often found outdoors, perhaps in the woods, feeding on dead animals. House flies, on the other hand, feed on food wastes and other garbage and can be found in and around the home and garbage containers. The house fly is also strongly attracted to locations where animal feces are abundant which includes barns, cow pastures, chicken coups and the like. Disclosure of the Invention ect............
https://patents.google.com/patent/WO1999022596A1/en
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she also had a brew made with the leaves and she had her bathing cossie with her so the old plunge pool would have come in handy. 
