The so-called short-horned locusts are frequently, for convenience sake, regarded as comprising two classes: the true locusts (Arabic: Girad) and the short-horned grasshoppers (Arabic : Gabura). It is difficult, however, to find definitions of these classes by means of which every species may be correctly assigned to its true place. The swarming habits of the true locust are often cited as connoting this class only, involving, as these habits do, the periodical appearance of excessive numbers of both hoppers and adults. Moreover the true locust is gregarious, in that the hoppers move in bands from one place to another, and the adults fly in vast swarms often over long distances. The fact that the grasshoppers are solitary in habit and manifest mutual independence of action is often taken as their chief distinguishing character. There is no doubt that these features do partly separate these two classes of insects from each other, but there are certain species which appear to occupy a position intermediate between the two. One normally solitary may, in certain circumstances, multiply rapidly and give rise to hoppers, which in certain respects act like those true locusts. Moreover the winged adults may undertake short massed flights resembling the migrations of swarms. On the other hand the fact, now fully established, that most true gregarious locusts have their solitary forms, which never associate, places even them in this respect with the grasshoppers.