"The family Tabanidae of the order Diptera contains those flies which are generally called horseflies or deerflies. As these common names indicate, the importance of the family lies largely in its relation to the welfare of livestock and wildlife. This would, in itself, be enough reason for undertaking a study of the tabanids. However, in addition to their importance to domestic animals, the Tabanidae are important to man's own welfare in many areas of the world. Tabanids serve as vectors of approximately eight different diseases which attack both man and animals. Their fierce biting and voracious appetite cause great economic loss by decreasing considerably the value of livestock, which are often under attack by great numbers of these flies. Their "nuisance value" decreases appreciably the efficiency of outdoor labor, and lessens the utility of outdoor recreational facilities. These are some of the reasons why a systematic study of the family Tabanidae should be made. We can control these flies only if we know what we are fighting, and which stage of the life cycle of the fly is most vulnerable to attack. Thus both taxonomy and morphology should be considered in such a survey. When I undertook this study, I was also motivated by the fact that the Tabanidae of this area have not been catalogued."--Introduction.