How to Make a Fly Trap
from a Quart Jar
Take a quart jar with a metal lid.
Punch four holes in the lid about the diameter of a fly (with the edges of the hole pointing into the jar). A large nail (and hammer) will work fine for punching the holes. In the example below, I used a medium screwdriver.
Note 1: Before you punch the holes, screw the lid back on the jar, so the lid is supported and will not crumple from the blow.
Note 2: Be careful! You will be dealing with glass and sharp metal edges. Unless you can handle these materials safely, do not undertake this project!
Note 2: Be careful! You will be dealing with glass and sharp metal edges. Unless you can handle these materials safely, do not undertake this project!
If the edges of the hole open out too much, use needle-nosed pliers to bend them back toward the opening, so they form a bit of a shaft, or a slight funnel. (See second photo below.)
 |  Close-up of a hole, shown from beneath, showing the edges that point into the jar. |
Put a small amount bait in the jar -- such as a half-teaspoon of canned dogfood.
Set the jar upright near a place the flies congregate -- such as next to to dogfood bowl. Flies crawl in, attracted by the smell, then have trouble finding their way back out.
Here's a jar turned on its side (to photograph it), showing three of the flies inside, some dog food, and part of a drippy eggshell used for bait.
When the bait gets too rotten, the jar gets too full of flies, or maggots hatch out, squirt a little dish detergent into the holes and fill the jar with hot water to kill everything in it.
If you are not comfortable with this step, then this kind of fly trap is not for you.
Then remove the lid, rinse out the jar, and start over.
-- Gerald Grow �2008