OF THE PAST. 219 



Insects. TJie more we learn of caenozoic Insects, the more truly 

 do we find that the early Tertiary period was in truth the dawn 

 of the present, the distinction between the faunas of these 

 remotely separated times (though not to be compared in 

 character) being scarcely greater than is found to-day between 

 the Insects of the temperate and torrid zones. 



We began this review with the statement that no Insect was 

 so important palaeontologically as the Cockroach. This would 

 more clearly appear had we space to pass in review the geologi- 

 cal history of all the Insect tribes; for then it could be shown 

 that it was only in the passage from palaeozoic to mesozoic times 

 that the great ordinal groups of Insects were differentiated, and 

 that the Triassic period therefore becomes the expectant ground 

 of the student of fossil Insects. Up to the present time we do 

 not know half a dozen Insects besides Cockroaches from these 

 rocks. Yet, notwithstanding this advantage on the part of the 

 Cockroaches, how meagre is the history, how striking the 

 "imperfection of the geological record" concerning them, the 

 following tabulation of the fossil species by their genera will show. 



It here appears that there are about 80 species known 

 from the palaeozoic rocks, two or three more than that from the 

 mesozoic, and only nine from the csenozoic ! When we call to 

 mind that half the palaeozoic Insects were Cockroaches, and that 

 seven or eight hundred species exist to-day, what shall we say 

 of the paltry dozen* from the rich tertiaries ? Shall we claim 

 that these figures represent their true numerical proportion to 

 their numbers in the more distant past? Then, indeed, must 

 the palaeozoic period have been the Age of Cockroaches ; for all 

 research into the past shows that a type once losing ground 

 continues to lose it, and does not again regain its strength. 

 The Cockroaches of to-day are no longer, as once, a dominant 

 group ; they are but a fragment of the world's Insect-hosts ; 

 yet even now the species are numbered by hundreds. If this 

 be a waning type, what must its numbers have been in the far- 

 off time, when the warm moisture which they still love was the 

 prevailing climatic feature of the world ; and how few of that 

 vast horde have been preserved to us ! The housekeeper will 

 thank God and take courage. 



This includes all possible forms ; our table shows but nine. 



