The Flight Interception Trap or FIT is a widely used trapping system for flying insects. It is especially well-suited for collecting beetles, since these animals usually drop themselves after flying into an object, rather than flying upward (in which case a Malaise trap

Malaise trap

A Malaise trap is a large, tent-like structure used for trapping flying insects particularly Hymenoptera and Diptera. The trap is made of a material such as terylene netting and can be various colours. Insects fly into the tent wall and are funnelled into a collecting vessel attached to highest point...

 is a better option). Flight Interception Traps are mainly used to collect flying species which are not likely to be attracted to bait

Bait (luring substance)

Bait is any substance used to attract prey, e.g. in a mousetrap.-In Australia:Baiting in Australia refers to specific campaigns to control foxes, wild dogs and dingos by poisoning in areas where they are a problem...

 or light.

Construction

The basis of any Flight Interception Trap consists of an upright placed see-through barrier under which one or more small basins are placed. The barrier may consist of such materials as plastic mesh

Mesh

Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to web or net in that it has many attached or woven strands.-Types of mesh:...

, a transparent plastic sheet or even plexiglass, although the latter works not for day-active insects since it is visible to them due to its specific refraction

Refraction

Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

. The basins are filled with a preserving fluid such as ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 (which should be mixed with something bad-tasting (like denatonium

Denatonium

Denatonium, usually available as denatonium benzoate and as denatonium saccharide, is the bitterest chemical compound known; with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharide.It was discovered in 1958 during research on local anesthetics by Macfarlan...

) to prevent wild animals drinking it), propylene glycol

Propylene glycol

Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound with formula C3H8O2 or HO-CH2-CHOH-CH3...

, salt-saturated water or even plain water. The best preservative to keep internal organs in good condition is FAACC, a solution of formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

. A small amount of detergent

Detergent

A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

 is added to break the surface tension

Surface tension

Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...

, causing the insects to sink.

Location

Depending on either the desired information (for research) or desired species (for trade) the construction can be put in open land or in the forest. It is important to place the barrier in a straight angle with the most likely flying route for insects (e.g. blocking a forest corridor), such as to maximize results.

Checking

The basins can be checked daily (when it is e.g. important to check the activity of the desired insects under different weather conditions), weekly or even less often. Maximum time between two checks depends on the used preservatives, since not all preservatives are equally suited for preserving insects for a longer time.

Cover

To prevent the basins from filling up with litter, most researchers place some kind of roof over the trap. This keeps leaves from falling in while it also keeps the rain out (which could otherwise dilute the preservative or cause an overflow).