This section of the book gives an outline of the major groups of insect that feed on blood, concentrating on those groups that are habitual blood feeders. Detailed coverage of each blood-sucking group is not attempted; that would far exceed the space available in a book such as this. Instead, this chapter has been written as a quick reference section for those new to medical and veterinary entomology and for those who need a quick outline of a particular group in order to make most use of other parts of the book. A basic outline of each assemblage is given, covering the essential details of the group's medical and veterinary importance, morphology, life history and bionomics.

Insects are individuals, and even within a single species insects often do things in subtly different ways from each other; this is, after all, a prerequisite for evolution. Consequently, generalizing about a genus, family and whole class of insects is an imprecise business, but bearing in mind that there are many exceptions to these generalizations, this approach can still be a good way of introducing typical group characters. In discussing each group, quantitative values are often given for fecundity, duration of each stage in the life cycle, longevity, etc. These figures are good guidelines to expected values under optimum conditions, but in the field one can expect a good deal of variation.