Townes' Style Malaise Traps
The Townes style Malaise trap is a tent-like structure, which is open on two sides to allow insects to enter. Once inside the trap, insects will hit one of the vertical walls, usually the central panel, and migrate up to the roof of the trap. Due to the slope of the roof they are directed towards the collecting head. The head is partially filled with a preservative, usually ethyl alcohol, and this is emptied at intervals. These intervals are usually last a week or two, but some service the traps every day.
Besides the Townes style Malaise trap you will need the following items:
14 tent pegs (short sticks cut at the site may also be used).
One 7.5 to 8 foot extendable aluminum pole (a sapling found near the site may be used, and it is also possible to use a small tree without cutting it.)
One 4 foot pole (a stick may be cut on site).
About 100 ft. of string.
Site selection: Place the trap along an insect flight path, e.g., along the edge of a forest and a meadow. The higher end of the trap (hereafter referred to as the anterior end) should be positioned such that it gets the maximum amount of light; in the preceding case this would mean away from the forest and into the meadow.
Place the trap on the ground and place a stake through the loop at the bottom of the middle of the posterior end (lower end) of the trap against the edge of the forest. Stretch out the trap and place another peg at the base of middle of the anterior end.
Position the anterior and posterior panels perpendicular to the central panel and peg the bases into the ground.
Place a pole 7.5 to 8 ft. high about 3 inches from the anterior end of the trap. Tie a 3 foot (39cm.) piece of string to the plastic ring that is on the collection head (bottle). Stretch the anterior end of the trap vertically and attach it to the pole with the string. An extendable aluminum pole, available in most camping store may be used. If a wooden pole or sapling is used it may be necessary to cut a notch to prevent the string from sliding. Depending on the site, the anterior end of the trap may be attached to a tree instead of a pole.
The pole must now be secured to a nearby tree or to the ground. If it is pegged to the ground a long line must be used. The line should be tight when the pole is held vertically.
The posterior end of the trap must now be secured in a similar fashion using a pole at least 4 ft. high. The pole is tied to the loop on the top of the posterior end of the trap.
The four corners of the roof are secured such that they are aligned with the anterior and posterior panels, perpendicular to the central panel. They can be attached to pegs in the ground, in which case the lines must be long to maintain the proper pitch in the roof. They can also be attached to nearby vegetation, or poles can be set up at each corner and fastened to the trap in a similar fashion to the anterior and posterior ends (see step 4).
It is now time to make minor adjustments to the trap. Hopefully you have tied proper knots so that the tension can be adjusted.
Place ethyl alcohol or some other preservative in the lower bottle of the collection head. If you wish to have specimens that are of a quality suitable for DNA sequence data, 95% alcohol is best, otherwise you can use a concentration as low as 70%.
Replace the alcohol at intervals. The timing of the intervals is site specific and it depends on the amount of insects that are captured, the ambient temperature, and the quality of specimens that are required. A maximum interval of 2 weeks is suggested.
The lower bottle may be wrapped in tin foil to prevent excessive evaporation of the alcohol.