I grow potted trees in zone 5 of northeastern USA and spend time watching the nature around them. I have been trying to learn more about the insects that frequent the plants, whether for good or bad.
In early summer I was regularly seeing the insect shown in photos below. I still see it sometimes, but not as frequently. I couldn't tell that it was hurting any leafs but it was putting its mouth to the leafs as if eating or sucking on something. Is it helping (protecting from other pests) or hurting (being a pest) the leafs? Its mouthparts and coloration are not like mosquitoes' but it otherwise its form is similar to one. It seemed to land on various leafs and trees in different areas of the garden but I noticed it most on hazelnuts (maybe just by chance).
A related question, maybe better a separate question, is how do you learn all the insects that frequent your plants? Are there good resources or methods to ID insects in a garden?