Entomologists collect specimens either actively or passively. The active collection methods include nets, beating sheets, sifters and separators. A net can be an aerial net, which an entomologist uses to sweep through the air to collect insects such as butterflies, a sweeping net for picking up insects in vegetation or an aquatic net for collecting insects in water.
Passive collection involves traps to concentrate insects for the entomologist to collect later. An interception net catches flying insects and funnels them into a collection jar or even kills them on contact with the insecticide-coated net. A window pane trap is a pane of glass suspended in the air so that flying insects hit the glass and drop into a container of killing liquid below.
A malaise trap is a partly enclosed net system that channels insects into a collection jar. A pitfall trap is set into the ground and allows crawling insects to fall through the trap into a killing liquid. Some ground traps are called Moericke traps, and are brightly colored pans filled with liquid so insects walk toward the color and fall in.
Emergence traps are sheets set above an area where young insects are growing. The sheet traps the immature insects when they emerge and can also be used for rearing live specimens. Entomologists also use light to attract insects into various traps. Insects can also be caught on sticky traps and electrical grid traps.
Baiting traps draws more insects than would normally enter a trap. Baiting methods include light, color, insect sounds (suitable for grasshoppers), pheromones, feces (suitable for flies), oatmeal (suitable for crickets, ants and cockroaches) and sugar (suitable for moths).
Agricultural and ecological entomologists kill insect specimens with 70 percent alcohol or other liquid or gaseous chemicals. If the scientist is going to perform genetic analysis of the insect, he will preserve it using about 100 percent alcohol.
Before the entomologist mounts the dead, dry specimens, he needs to relax the body by placing it into a high humidity chamber for about eight hours. Then he can pin the body onto a cork or other soft base. He then examines the specimen using a magnifying glass or a microscope.
The correct method for picking up insects is to use a fine forceps. For tiny specimens, entomologists use a fine-haired brush to pick up the insect. A safe storage method for specimens is to place them into small boxes with a cloth or tissue packing. Entomologists also use knives to open pods or seeds to check for insects inside, which is especially useful in agricultural entomology.