Hemielytron is singular, hemielytra is plural. This is a description of the wings of the only insects that you can correctly call "bugs," the true bugs, order Hemiptera. The order name Hemiptera also refers to the structure we're discussing, it is greek for half-wing, i.e. the anterior half or corium is hard (sclerotized) or leathery, the posterior half is membranous. The hindwings are the major flight power and are entirely membranous. True "elytra" are, incidentally, completely leathery or hard and are the modified forewings or wing covers, if you will, characteristic of the order Coleoptera, the beetles. I am an entomologist, and this information can be found in any decent entomology textbook or website, see the reference below for a definition of the clavus. The remaining terms (pronotum, scutellum, etc.) are also used in their Latin forms in English exactly as they are in German, and you can just translate literally the German names in parentheses into English and be right on the mark, as they are just descriptive or explanatory and are not used by scientists. Because wing structure is a very noticeable, distinguishing characteristic of many insects, most insect orders and many other taxa are classified on their wing structure (or absence thereof); the Greek ending -ptera (wing) is attached to most insect order names.