A tailor is preparing to eat some jam, but when flies settle on it, he kills seven of them with one swipe of his hand, or "blow." He makes a belt describing the deed saying "Seven at one blow."
I found these sticky tape which is very good to snare them, on the first day, we caught 20 villains.
http://abcwednesday-mrsnesbitt.blogspot.co.nz/