We have these blue-ish wasps on our fence at dawn and evening times (cooler and barely any sun)?

Question

They look like wasps. Not too agressive, they swarm around when disturbed. One day last year when it was cooler, I bumped the fence when they were hiding and "sleeping" and lots just fell out onto the grass, so i mowed em up. I think it was 2 cold 4 them 2 fly. Any ideas what they are and how to get rid of them, they are gone during the day maybe in the field behind our house. Then they return flying around on the fence when the sun is setting. Kind of a metalic blue color with two sets of black winfs that fold into two strait lines down back.

Answer 1

Digger or Threadwaisted Wasps

Both the blue digger and golden digger wasp are beneficial, appearing in the morning and flying over the lawn all day, then leaving in early evening. Digger wasps are solitary wasps with each female working alone to produce her offspring instead of having the help of several workers as in social chambers or cells. These chambers are provisioned with food for the offspring. After the eggs are laid in or on the "provision," the offspring are on their own to live and grow to adults that emerge the following summer.

The blue digger about 3/4-inch long is shiny metallic blue on both the wings and body. This slender wasp provisions its nests with grasshoppers and crickets. Also, the inch-long golden digger wasp with shiny gold markings on the face and abdomen uses grasshoppers and crickets as stored food for their offspring. Often, wasps can be seen flying about a foot or less above the ground. Others may be perched on shrubs and trees.

Due to their large size, they are assumed to be extremely dangerous. Actually, they are not aggressive but curious and investigate persons and pets near their burrows. Stings are quite rare. One can walk safely through them as they hover over the lawn.
Control

If ground-nesting bees and wasps can be ignored and their tunnels tolerated, do so since they are valuable in agricultural production and helpful by controlling pests in nature. If nests are in locations undesirable and stinging is a great possibility, control is justified. During the day, carefully watch where the nest entrances are located. After dark, tunnels and the surrounding area can be treated with dusts of carbaryl (Sevin), bendiocarb (Ficam D) or diazinon when the nest is in the ground. Use pyrethrins, permethrin, resmethrin or propoxur (Baygon) when the nest is in the side of a building. Other lawn and garden insecticide sprays can also be used, but dusts have the advantage of not soaking into the soil. Those who are allergic to bee stings, should contact a licensed, professional pest control operator to perform the control job. Always read the label and follow directions and safety precautions.

Answer 2

You should be able to a wasp and hornet spray at a local hardware or home and garden center near you. Just spray it on them while they are in the nest. Do this during the cooler times of day, early morning or late evening. Spray as heavily as you can and be ready to run.
I get several varieties of them here and have to spray for them several times a summer.