When teaching about insects, biologists almost never say “always” or “never.” The words “almost always,” usually,” “most often,” “generally,” “ordinarily,” and “normally” can save a lot of trouble because in biology, there is “almost always” an exception to every rule.
Take, for example, the characteristics that separate insects from other classes of animals. Insects are normally ectothermic or cold blooded, thus requiring the sun to warm them to activity. They ordinarily have six legs; usually three main body parts, including a head, thorax and abdomen; generally have four wings and normally lay eggs rather than give birth to living young. However, it seems that every rule has an exception. If you are one who likes to put all of biology into tight little black and white boxes, exceptions are frustrating until you become comfortable with what I call biological hedge words.