Sight capture is the basis of entomology. It requires the skilled eye of the entomologist, capable of spotting insects or their traces, and the use of nets. They are of two main types: the so-called butterfly net for catching insects in flight or on a surface and the mowing net for reaping weeds. Light and stiff, the butterfly net is about two and a half times longer than its diameter. A smaller diameter allows a greater reactivity by reducing the volume of circulating air and limiting the inertia. Its handle, in aluminum or fiberglass, must be 31.4 to 39.3 in (80-100 cm) long to help control the movement better. As for the mowing net, more solid and heavier, it allows capturing the insects in the weeds and making them fall to its bottom through a back and forth movement.