CHAP, vin ORTHOPTERA 199 



The changes of form that accompany the growth of the 

 individual are much less abrupt and conspicuous than they are 

 in most other Insects. The metamorphosis is therefore called 

 Paurometabolous. It has been supposed by some naturalists that 

 Orthoptera go through a larger portion of their development in 

 the egg than other Insects do. This does not clearly appear 

 to be the case, though it seems that there are distinctions of a 

 general character in the embryology ; the period of development 

 in the egg is prolonged, and the yolk is said by Wheeler 1 to be 

 more than usually abundant in comparison with the size of the 

 young embryo. The embryonic development may in tropical 

 countries be accomplished in three weeks (see Mantidae), but in 

 countries where winter supervenes, the period may in some 

 species be extended over seven or eight months. 



The external features of the post-embryonic development a 

 term that is more convenient in connexion with Orthoptera than 

 metamorphosis are as follows : the wings are never present when 

 the Insect is first hatched, but appear subsequently, and increase 

 in size at the moults ; the form and proportions of the segments 

 of the body especially of the thorax undergo much change ; 

 an alteration of colour occurs at some of the moults, and the 

 integument becomes harder in the adult condition. Neither 

 the development of the internal organs, nor the physiological pro- 

 cesses by which the changes of external form are effected, appear 

 to have been studied to any great extent. 



Many of the Orthoptera do not possess wings fit for flight, and 

 some species even in the adult state have no trace whatever of such 

 organs. Flight, indeed, appears to be of minor importance in the 

 Order; in many cases where the wings exist they are purely musical 

 organs, and are not of any use for flight. The apterous and the 

 flightless conditions are not confined to one division of the Order, 

 but are found in all the families and in many of their sub- 

 divisions. As the front pair of wings in Orthoptera do not really 

 carry out the function of flight, and as they differ in several par- 

 ticulars from the hinder pair, or true wings, it is usual to call 

 them tegmina. The musical powers of the Orthoptera are confined 

 to the saltatorial group of families. The Cursoria are dumb or 

 nearly so ; it is a remarkable fact that also in this latter division 

 the alar organs, though frequently present, have but little value 

 1 /. Morphol. viii. 1893, p. 64. 



