Three fly bottles, Central Europe, beginning of the 20th century
A fly bottle or glass flytrap is a passive trap for flying insects. In the Far East, it is a large bottle of clear glass with a black metal top in which there is a hole. An odorous bait is placed in the bottom of the bottle in the form of pieces of meat. Flies enter the bottle in search of food and are then unable to escape because their phototaxis behavior leads them anywhere in the bottle except to the darker top where the entry hole is.[5]

A European fly bottle is more conical, with small feet that raise it half an inch, with a trough about an inch wide and deep that runs inside the bottle all around the central opening at the bottom of the container. In use, the bottle is stood on a plate and some sugar is sprinkled on the plate to attract the flies, which eventually fly up into the bottle, whose trough is filled with beer or vinegar, into which the flies fall and drown.[6] In the past, the trough was also sometimes filled with a dangerous mixture of milk, water, and arsenic or mercury chloride.[disambiguation needed][7]

Variants of these bottles are the agricultural fly traps used to fight the Mediterranean fruit fly and the olive fly, which have been in use since the 1930s. They are smaller, without feet, and the glass is thicker for rough outdoor usage, often involving suspension in a tree or bush. Modern versions of this device are often made of plastic, and can be purchased in some hardware stores. They can also be improvised from disposable plastic drink bottles.