You have a heron is my guess

Glass can change color in natural ways. Exposure to sunlight can change the color of glass as will exposure to soil. Jars buried in the soil can become iridescent. These are all natural chemical reactions and vary depending upon external conditions and the minerals in the glass. An example would be a kerosene lamp which turns purple as it ages due to a chemical reaction between sunlight and the manganese in the glass. I don't know how it's currently made, but I know Ball used to use a certain % of cullet in its glass jars and the chemical composition would vary depending upon the source of the purchase. Cullet is broken old glass (like windows or soda bottles, etc.) which is mixed with the fresh ingredients to make "new glass." The cullet is required to assure an even melt in the furnaces. So all canning jars have some slight variation in the chemical composition depending upon the composition of the broken glass being used and that influences the response of the glass to sunlight, minerals (like that in dishwasher detergent or water) or soil. It's not harmful and there's no reason not to use the jar but my inclination would be to use it in boiling water bath rather than pressure canner in case the iridescence is due to excessive heat, which might have weakened the glass. Carol

Yes. Other names are flower fly and syrphid fly.

The angle of incidence is more important than the type of light. Halogen lights produce the highest amounts of heat which will be felt in the cabinet space above.