33 



only in tropical regions. British cockroaches, too, lack the beautiful 

 colours sometimes found in foreign species. 



In the Silurian sandstone of Cavaldos, in France, the late M. 

 Brogniart found a fossil, which he considered to be part of an 

 elytron of a cockroach, and named it Pahroblattina doui-illti. Brauer, 

 however, thinks it more probably belongs to an msect like the mole- 

 cricket, while Sharp inclines to the opinion that it does not belong 

 to the Insecta at all. If there were no doubt concerning the iden- 

 tification this fragment would represent the oldest insect known. 



It is in the Carboniferous period of Paljeozoic times that cock- 

 roaches first appear with certainty upon the scene — or rather, that 

 evidences of them first appear, which is probably a very different 

 matter. The coal-measures of Great Britain, Belgium and Ger- 

 many, and the coal-measures and mill-stone grit of America, have 

 supphed a great number of cockroaches, which group of insects 

 appears to have been more numerously represented and more 

 generally distributed than any other at this period, which in fact 

 has been called the " Age of Cockroaches." The Permian period, 

 has produced but few insects, though amongst them are several 

 specimens of the Blattodea; but apparently none have come to light 

 in this country. 



Passing to Mesozoic times the Triassic rocks of America have 

 produced a number of specimens of the Blattodea, but this is not 

 the case in Europe. In the Lias fossil insects are numerous, and 

 specimens of those w^e are considering are represented both in 

 Britain and on the Continent. The Purbeck beds of the Upper 

 Oolite have preserved several species, but they appear to be absent 

 from the Cretaceous formations, as we should expect, seeing that a 

 large proportion of these rocks are of marine origin and were 

 deposited in deep water. 



In Cainozoic times the Eocene period does not seem to have 

 produced fossil cockroaches in Britam, but perhaps the conditions, 

 under which the formations during the period were deposited, were 

 not favourable to their preservation. 



The rest of the Tertiary formations are absent from, or not well 

 represented in Britain ; but the Blattodea have left some remains in 

 Miocene strata en the Continent, and a few have been preserved in 

 amber, In the Post- tertiary period fossil insects are rare, except 

 Coleoptera, to which order all must perhaps be referred. 



Judging by the wings, from which almost entirely our knowledge 

 of fossil cockroaches is derived, these insects are found to bear a 

 close general resemblance to recent forms. They, however, present 

 three important differences. First, the elytra and wings were 

 similar in appearance and transparent ; second, the same number 

 of nervures was developed in both, whereas in recent forms they are 

 reduced in number in the elytra ; third, the arrangement of the 

 nervures in the anal area was different. The wings rather than 

 the elytra of recent cockroaches preserve more closely the appearance 



