The picture shows a Skipper inserting its sucking tube into one of the hundreds of flowers comprising a Dandelion flowering head. Some sucking tubes swing up beneath the insect when not in use, as in assassin bugs, and other tubes store in a neat coil, as among butterflies and moths. Skippers are intermediate forms between butterflies and moths, so their tubes curl beneath them. Legs are important in insect identification, especially the tarsus part, which more or less corresponds to a jointed foot. As with antenna segments, it's often important to notice how many segments comprise the tarsus.
Wings are the very books in which the identities of many insect groups are written.
Good insect field guides include drawings such as those to the right, showing how the wings' individual veins connect with one another. And each vein and each cell has it own name. In the drawing at the right it's easy to find the difference between the Common House Fly of the genus Musca , or the Little House Fly of the genus Fannia . To get a better feeling right now for insect structure and design, you might want to surf to Iowa State's bug-site called the Insect Image Gallery , where you can see lots of insect types.