BLATTID.E PRESERVED IN AMBER, FROM PRUSSIA. 337 



Of these genera, Edohius at the present day is confined to Europe and 

 tropical Africa ^ ; Tschnoptera, Pliyllodromia, Cerathioptera, and Teinno- 

 pteryx occur in all the tropical regions, in Australia, and in the southern 

 half of the Nearctic region ; Nyctibora is a characteristic Neotropical genus ; 

 Periplaneta, if we exclude the cosmopolitan species distributed by the 

 aoency of man, is a tropical and subtrojjical genus ; Polyphaga is found 

 in the southern and extreme eastern parts of the Palsearctic region, in 

 Africa, and sporadically in the Oriental region ; Holocompsa is Neotropical, 

 Ethiopian, and Oriental in its distribution. It must be remembered that the 

 species of cockroaches preserved in amber are, with one exception, of small 

 or moderate dimensions ; there are none rivalling in size the species of 

 Blabera from S. America, or of JSauplioeta from tropical Africa. Large 

 robust species if entrapped in the sticky resin exuding from the trees of the 

 Oligocene forest would be able to break away and escape the doom that 

 awaited more fragile species. That species of considerable size did exist 

 side by side with smaller forms is indicated by the presence in Dr. Klebs's 

 collection of a large larval moult which I refer with some little doubt to the 

 genus Nyct'xhora ; judging from the general appearance of this specimen, I 

 do not consider it to be a final moult, and there is every reason to suppose 

 that the adult was not inferior in size to modern representatives of the genus. 

 There can be little doubt that if the larger species of the amber fauna had 

 been preserved they would have supplied additional evidence of its affinities 

 with a modern tropical fauna. 



A comparison of the amber-enclosed Blattidpe with the paucity of species 

 occurring in Northern Europe at the present day is sufficiently indicative of 

 the profound change of climate that has ensued within geologically-recent 

 times. Of the 9 genera found in the amber fauna, only one f has persisted 

 in N. Europe to the present day ; and that one is Ectohius, represented in the 

 amber fauna by two species, in modern times by three N. European forms. 

 At one time 1 was inclined to regard the two Oligocene species as a purely 

 Pala^arctic element in a tropical fauna and was puzzled to find a reasonable 

 ^explanation of their presence. But since then I have examined a good many 

 collections of Blattidse from tropical Africa and there is no doubt that the 

 genus Ectohius is well I'epresented on that continent, though all but one of 

 the species are undescribed. It is clear, then, that Ectohius is not purely a 

 genus of temperate or subarctic regions and its presence in the amber fauna 

 is not a matter for very great surprise. At the same time the two species 

 of the amber fauna appear to be more closely related to the well-known 



* I have recently liad the opportunity of examiuing the types or co-types of species from 

 Australia and New Zealand which have been referred to Ectohius ; not one of these belongs 

 even to the subfamily Ectobiince. 



t Pliyllodromia germanica is not included ; it is a cosmopolitan species whose centre of 

 disuersal is not known. 



27*' 



