INTRODUCTION. 3 



early date, were liighly specialised. The elaborate 

 veining of the wing of Xenonenra antiqiwrum, which 

 apparently points to a family combining characters of 

 a chirping cricket (Orthoptera) and a water-fly (Ephe- 

 mera)^ leads to the probability that far more simple 

 forms preceded such, about which there is now no 

 record. 



As might have been expected, the Coleoptera are 

 the most fully represented in a fossil state ; their dense 

 elytra and their hard exteriors are less open to disin- 

 tegration than the softer bodies of the Hemiptera and 

 Lepidoptera. The Hemiptera would appear to be not 

 much less ancient than the Orthoptera, for they have 

 been found in the Carboniferous beds of Great Britain 

 and America. Singular unions of type again show 

 themselves in certain examples from the Permian 

 strata ; such having in their mouth parts, compounded 

 characters of the mandible and haustellum. Both the 

 Orthopterous and Hemipterous orders are represented 

 in the genus Eugeria. 



Most of the strata in an ascending series from the 

 Devonian, show more or less an abundance of insect 

 remains, but perhaps the Liassic and Oolitic forma- 

 tions are most remarkable for the number of species.* 



The occurrence of the Hemiptera-Homoptera in a 

 fossil state is much less frequent than that of the 

 Hemiptera-Heteroptera. According to some we find 

 their first appearance as the interesting Palceonfina 

 oolitica, which occurs in the Stoneslield roofing- 

 stone. 



But whether or not this form has been rightly 

 classified, the Homoptera are clearly represented in 

 the insect limestones of Wiltshire and Dorsetshire. 

 In the Purbeck beds of these counties even the small 

 and frail bodies of the Aphididae have left their impres- 

 sions on the soft mud. These are accompanied by the 

 allied Homopterous families of the Cicadidee and 



* Prof. Oswald Heer, ' Die Urwelt der Schweiz.,' 1865. Translated 

 by W. S. Dallas, 1876. 



