354 The Pedigree of Insects 



transparent wings with simple orthopteroid neuration, 

 and a pair of long, jointed cercopods. 



Nearer to the Platyptera, also, than to any other 

 living insects, must be placed an extinct Carboni- 

 ferous group (3, 204) including the genera Corydaloides, 

 Lithomantis, Dictyofieura, and Haplophebium. Many of 

 these had paired veined outgrowths on the hind-body 

 segments, which have been interpreted as tracheal 

 gills comparable to those found on the imago of the 

 living Perlid Pteronarcys, but more numerous, much 

 more highly developed, and undoubtedly functional. 

 Some of these ancient insects moreover had short wing- 

 like expansions on the pronotum. They had two pairs 

 of large membranous wings, and it is hard therefore 

 to believe that they were aquatic in habit when adult. 

 Probably the gill-like plates on the abdomen were of 

 use in breathing damp air, and may have been survivals 

 from a larval stage passed in the water. Or these 

 paired outgrowths on the first thoracic and the 

 abdominal segments may perhaps suggest that the 

 rudiments of wings appeared on every segment of the 

 primitive insect's body, but that only on the meso- 

 and the metathorax did they develop into organs of 

 flight. 



Some insects {Homalotieura, etc.) of Carboniferous 

 age, closely resembling those just described, with 

 similar fore- and hind-wings and prothoracic and 

 abdominal wing-rudiments or gill-plates, have been 

 regarded as the ancestors of Mayflies. These Prot- 

 ephemerida had excessively long cercopods. They do 

 not show, however, any other characteristic ephemerid 

 features ; and they can have had but little to do with 

 the origin of Mayflies if the contemporary Carboniferous 

 Palingeiua Feistmantelli is rightly referred to an exist- 

 ing genus of Ephemeridfe. There is no doubt that 

 Mayflies closely resembling those now living were 



