CHAPTER IV 

 PALEONTOLOGY 



Introduction, p. 72. Orders only Known as Fossils, p. 74 

 Pakeodiciyoj^tera, p. 74 ; Protorthoj)tera, p. 75 ; Megasecoptera, p. 77 ; 

 Protodonata, p. 79 ; Proioj^erlaria, p. 80 ; Protohcmiptem, p. 81 ; 

 Protocoleoptera, p. 82 ; Protelytroptera, p. 83 ; Incertce Sedis, p. 84. 

 The GeologiCxVL History of Insects, p. 86. Devonian, p. 86 ; 

 Carboniferous, p. 86 ; Permian, p. 87 ; Trias, p. 90 ; Jiirassie, p. 90 ; 

 Cretaceous, p. 92 ; Tertiary, p. 92. The Phylogeny of Recent and 

 Fossil Orders of Insects, p. 94. Literature, p. 102. 



Introduction 



In the fossil condition insects are only found in certain geological 

 strata especially favourable for their preservation. Under such 

 conditions they are often abundant, and this appears to be due to 

 the probability that most of the specimens got drowned and were 

 quickly covered with silt or other deposit before their remains 

 had time to decay completely. Some of the richest stores of fossil 

 insects are consequently found either in vegetable deposits like 

 coal, lignite and peat, or in ancient freshwater basins. A great 

 many insects have also been found in amber, where they became 

 entangled in the resin which speedily enveloped them before 

 they had any chance of freeing themselves. Specimens sealed 

 up in and impregnated by this natural medium are retained in a 

 wonderfully perfect state of preservation. 



For the most part, insect fossils are represented by wings 

 only. It appears that under the conditions of fossilisation decay 

 speedily sets in, with the result that the bodies of the insects soon 

 disintegrated and became separated from the wings. The 

 lightness of the latter caused them to float away and to accumulate 

 in certain beds where their more durable structure enabled them 

 to resist destruction. The natural result has been that insect 

 palaeontology is mainly a study of venation, and knowledge of 



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