134 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



terior wings are fully developed. In the group of 

 Coleoptera (scarabs, cockchafers, longicorns, and 

 beetles), the anterior wings (" wing covers ") have 

 become very resistant, and constitute a perfect 

 cuirass covering and protecting the abdomen, and 

 the posterior wings, the organs of flight, are folded 

 beneath the wing covers when in repose. In the 

 Scarabsei and the Calosoma the posterior wings 

 are much reduced. In other Coleoptera the wing 

 covers are united by their inner edges, thus render- 

 ing all movement of the underlying wings ineffectual 

 and useless. The result may, as in Gfibbium, 

 be the total atrophy of these under wings. In 

 the Staphylinidse, the upper wall of the abdomen 

 is so strong that the protection of wing covers is 

 unnecessary; consequently the wing covers have 

 degenerated into little lamella which cover only 

 the anterior quarter of the body. In the female 

 Lampyris (glow-worm), the wings have totally dis- 

 appeared. The Orthoptera (cockroaches and ear- 

 wigs) exhibit a great number of variations in the 

 organs of flight. In cockroaches all four wings 

 are usually fully developed ; in some specimens, 

 however, and these principally female, a very pro- 

 nounced degeneration of all the wings may be 

 observed. The anterior wings of the Forficulides 

 are reduced. In the group of Phasmidse we find 

 side by side with species of the genus Bacillus, 

 which have no wings and look like dried twigs, 

 Phyllium siccifolium to which the large green and 



