EVOLUTION 



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types have been described by C. Brongniart (1894), A. 

 Handlirsch (1906-8), S. H. Scudder (1890), and H. Bolton 

 (1921-2), from European and North American localities. 

 Most of the insects of the Primary Era thus revealed are 

 referred to an order, Palaeodictyoptera, now altogether 

 extinct, characterised by the close similarity of the v^ings 

 of the two pairs and the presence of long, jointed tail- 

 feelers (cerci). Some students of these insects believe that 

 the wings were always spread out at right angles to the body 

 as they could not be brought together over the back. The 

 neuration was primitive, and in some forms there were small 

 paired plates, suggesting rudimentary wings, on the pro- 

 thorax as well as a series of paired lateral expansions (pleura) 

 on the abdomen ; these structures have led to speculation 

 as to the possibility of wing development on all segments 

 of the primitive insect's body. The Palaeodictyoptera, 

 some members of which (Dunbaria) survived until the 

 succeeding Permian Period, afford a possible origin for 

 most of the orders of winged insects living around us to-day. 

 It is noteworthy that in rocks of the same Carboniferous 

 Period are preserved remains of insects with broadened 

 hindwings and a type of neuration approaching that of 

 cockroaches ; these are referred to another extinct order, 

 the Protorthoptera. But in Carboniferous times lived also, 

 as we know from fossil evidence, insects (Plate XII) which 

 were so like modern cockroaches that it is doubtful if 

 they should not be placed in the same family. Thus we 

 realise that cockroaches w^ere crawling among the rank 

 vegetation of the ancient coal-forests, and that representa- 

 tives of the more primitive stocks whence they had sprung 

 were still surviving from earlier periods of the earth's 

 history, though as to those earlier periods there is as yet 

 no ^definite evidence from fossils. The Palaeodictyoptera 

 suggest an origin not for the Orthoptera only but for most 

 of the exopterygote insect orders. 



That the oldest winged insects must have arisen before 

 the period of the Coal Measures is shown by the fact that 

 contemporary with the Carboniferous Palaeodictyoptera 



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