The Locustidae are, as a rule, more fragile Insects than the Acridiidae, from which they can be readily distinguished by the characters we have mentioned in our definition. According to Dufour, there are no air vesicles connected with the tracheal system in this family; possibly to this it may be due that none of the family undertake the long flights and migratory wanderings that have made some of the Acridiidae so notorious. Very little is known as to the life histories of the members of this extensive family of Orthoptera. Graber, however, has given some particulars as to the development of _Platycleis grisea_, and of one or two other species. He recognises five instars, but his first is probably really the second, as he did not observe the Insect in its youngest condition. Although his figures are very poor, we reproduce them, as they give some idea of the mode of growth of the wings, and of the correlative changes in the thoracic segments. It will be seen that in the first three of these instars the alar organs appear merely as prolongations of the sides of the posterior two thoracic rings, and that in D a great change has occurred in the position of these segments, so that the alar organs are free processes, the two posterior thoracic rings being insignificant in size in comparison with the now greatly developed prothorax. In E the tegmen is shown fully developed, the positions of some {313}of the rings covered by it being indicated by the letters _m_, _mt_, _ab′_. These changes are very similar to those we have described in Acridiidae, the chief difference being the greater development of the dependent wing-pads previous to the fourth instar. [Illustration: FIG. 189.—Front of head of _Copiophora cornuta_, female. Demerara.] The ocelli in Locustidae are much more imperfect than they are in Acridiidae, and are frequently rudimentary or nearly totally absent, or there may be but one instead of three. They are, however, present in a fairly well-developed state in some species, and this is the case with the one whose face we portray in Fig. 189, where the anterior of the three ocelli is quite conspicuous, the other two being placed one on each side of the curious frontal cone near its base. The peculiar head ornament shown in this figure exists in both sexes, and something similar occurs in a large number of Conocephalides. We have not the slightest idea of its import. Individuals of one or more species of this curious South American genus are occasionally met with alive in gardens near London. They are, no doubt, imported as eggs, for they are sometimes met with in the juvenile state, but in what way they are introduced is not known.