To explain satisfactorily these complex life-stories is however admittedly a difficult task. The acquisition of wings is, as we have seen, a dominating feature in them all, but if we try to go yet a step farther back and speculate on the origin of wings in the most primitive exopterygote Bed Bugs, the task becomes still more difficult. Many years ago Gegenbaur (1878) was struck by the correspondence of bed bug wings to the tracheal gills of may-fly larvae, which are carried on the abdominal segments somewhat as wings are on the thoracic segments. But Brner has recently (1909) brought forward evidence that these abdominal gills really correspond serially with legs. Moreover Gegenbaur"s theory suggests that the ancestral Bed Bugs were aquatic, whereas the presence of tubes for breathing atmospheric air in well-nigh all members of the class, and the fact that aquatic adaptations, respiratory and otherwise, in bed bug-larvae are secondary force the student to regard the ancestral Bed Bugs as terrestrial. It is indeed highly probable that Bed Bugs had a common origin with aquatic Crustacea, but all the evidence points to the ancestors of Bed Bugs having become breathers of atmospheric air before they acquired wings. How the wings arose, what function their precursors performed before they became capable of supporting flight, we can hardly even guess.