Abstract: A trap for flies or other small insects or pests has an enclosure in which is normally maintained a static vacuum. A small opening, preferably with a cone-shaped corridor leading to the opening, has a closure door which when released will swing open and admit a high-velocity rush of air that will draw a fly from the corridor into the enclosure. A fly sensor, such as a motion detector or photodetector, determines the presence of a fly and relays this information to a CPU or a simply relay, which sends a signal to release a latch on the door, allowing the door to swing open. The enclosure's interior preferably includes an angled wall surface which the fly impacts at high enough speed to kill or stun the fly, and falls into a fly tray that can be pulled out for cleaning. A pest attractant such as a light or a smell attractant is included near the opening.