340 THE BIOLOGY OF INSECTS 



the presence of four types of undoubted Hemiptera — all 

 referable to the sub-order Homoptera — in the Lower 

 Permian beds of Kansas, North America. In Prosbole, 

 from the Upper Permian of Russia, there can be traced 

 the beginning of differentiation between the corium and 

 membrane of the forewing that characterises the Hete- 

 roptera. Our knowledge of the course of m.odification 

 in the wings of the Hemiptera is mainly due to the 

 researches of Tillyard (1918-19, 1926), who has discovered 

 ancestral Homoptera in the Upper Permian beds of 

 Belmont (New South Wales) and the Upper Trias of 

 Ipswich (Queensland) in some abundance, and in the 

 Trias, primitive Heteroptera, such as Dunstantia, more 

 sparingly. From rocks of Jurassic age in Europe have 

 been taken fossils that establish the presence of several 

 living families of Hemiptera at that period of the world's 

 long history. 



From the above summary it will be realised that our 

 knowledge of extinct Exopterygota supports the conclusions 

 as to the course of their racial development that may be 

 drawn from the comparative study of their structure and 

 life-history. The geological history of the metamorphic 

 insects (Endopterygota) now calls for attention. 



The combination of mandibulate jaws with four similar 

 membranous wings with predominantly longitudinal neura- 

 tion marks the Mecoptera as the most primitive living 

 representatives of the sub-class. Tillyard has lately 

 (1926) pointed out that the North American fossil Metro- 

 pator described by A. Handlirsch (1906) from the Upper 

 Carboniferous of Pennsylvania, " one of the eight oldest 

 insect wings yet discovered," must have belonged to a 

 Mecopteran. He has also described (1926) Mecoptera- 

 from the Lower Permian of Kansas ; belonging to extinct 

 families near those represented (Plate XII, C) in the Upper 

 Permian of New South Wales and allied to the Choristidae 

 which survive as members of the modern Australian fauna. 

 Contemporary with these Australian Permian Mecoptera 

 lived Belmontia, represented by fossil remains found at 



