Taken from:

http://bohart.ucdavis.edu/resources_howtocollect.aspx

Collecting Equipment

Insect Net

One of the most valuable pieces of equipment for studying insects is a net. A good net is one that is made of a mesh that is easy to see through, has a hoop and handle that are large enough to reach and catch the insects you would like to get, yet is not so large as to be difficult to handle. The length of the net bag should be long enough to fold completely across the hoop and still leave a pocket at the end where the insects are collected.

A net used for sweeping through dense vegetation should be made of a fine mesh so that it does not snag too easily, whereas a net used to sweep through the air (such as one used to catch butterflies or dragonflies) should be made of a coarse mesh so that it can move quickly without much air resistance. An entomologist may want to keep a variety of net bags on hand for various situations.

When collecting with a net, one may sweep through the air to catch a particular visible insect, or one may sweep through vegetation. The former requires some skill to catch the desired insect in flight, whereas the latter is simply a matter of swinging the net and catching whatever enters. When sweep netting through vegetation the bag should be emptied often to prevent damage to the specimens, especially by large pieces of plant material.

With either type of net collecting, one should take care to prevent the insects from escaping the net. One simple way is to fold the net over upon the rim of the hoop, with a flick of the wrist, quickly after sweeping (see drawing above). The insect (or insects) can then be grasped through the net (provided it is not a stinging insect) and transferred to a killing jar. If the insect is a stinging type, the insect may be folded into a portion of the net, and the entire fold may be stuffed into the killing jar until the insect is stunned, at which time it may be removed from the net and transferred to the jar. Insects may also be transferred to a killing jar by inserting the jar into the net. By holding the tip of the net up (because many insects move upward to escape) the lidless jar can be moved upward to trap the insect. The lid can then be worked onto the jar while still inside the net.

Aspirator

An aspirator is a useful device for catching small insects, especially those that rarely fly. Aspirators are used by sucking through a mouthpiece to draw small insects into a vial. Aspirators can be purchased at an entomological supply company.

Beating Sheet

Many insects feign death by falling to the ground when disturbed. A beating sheet is used for catching such insects that fall off of vegetation. A piece of sturdy canvas, sometimes on a wooden or metal frame, is typically held or placed under a plant to collect the specimens. The plant is then shaken or hit with a stick, causing the insects to fall. The insects can be picked off of the sheet with forceps and transferred to a killing jar.

Light Trap

An outdoor light that is turned on at night is a good way to collect insects. Since many insects navigate by the moon, they get confused by bright lights and are attracted to them instead. Try hanging a white sheet or cloth near a porch light or backyard light. You will find that many different kinds of insects, especially moths, will land on the sheet. They can be collected off the sheet by hand or with a pair of tweezers.

Pitfall Traps

Pitfall traps are used to collect insects that crawl along the surface of the ground. To make a pitfall trap, bury a plastic bowl (yellow or white seem to work best) up to the rim, so that the rim is level with the ground surface. Put enough water in the bowl to cover the bottom and put one drop of liquid soap in the water (to break the surface tension). Insects crawling over the surface of the ground will fall into the bowl and will be unable to climb out. Check the pitfall trap on a regular basis.

Tullgren Funnel

Collecting insects that live in soil or leaf litter can be quite tedious; however, by taking advantage of the fact that many of these insects are negatively phototaxic (avoid light) one may construct a simple mechanism to extract them. A Tullgren funnel is simply a large funnel (approx. 60 cm diameter at the widest point) with the narrow end inserted into a collecting jar. Some coarse wire mesh is placed inside the funnel; the mesh should be wide enough for insects to move through but coarse enough to support the soil or litter. The soil is then placed in the funnel (on the mesh), and a bright light is supported at the top of the funnel. The insects will move downward through the substrate to avoid the light (and heat) from above, and will eventually fall into the collecting jar.