OF DERMAPTERA. 108 



great winter epoch and the ensuing time and the contingencies are repre- 

 sented in a slight degree by the alternations of the seasons, by birds of 

 passage, and by the northward migrations of some southern inescts during 

 a hot season. The Dermaptera generally are more limited to warm regions 

 than are the other orders of insects, which also more or less precede them 

 in time of yearly appearance. Omitting all notice of the sinking of former 

 continents and of the rising of present continents and islands, a few words 

 may be said with regard to the way in which ramifications from the 

 Dermaptera in tropical regions have converged towards the poles. Some 

 tribes appear to have left their first habitation entirely as the increasing 

 heat and dryness deprived them of circumstances essential to their existence, 

 and some seem to have increased in numbers and variety after their migra- 

 tion. The advance to the north from the equatorial regions may be 

 included in four principal divisions: 1st, through China to Japan; 

 2nd, from the East Indies along the Himalaya and other mountain ranges 

 to West Asia and to Europe; 3rd, from Central Africa to North Africa 

 and to Europe ; 4th, from Equatorial America to North America. There 

 are many instances of one kind of insect being a native both of Japan and 

 of Europe, or of Europe and of the Mountains of Hindostan, and the close 

 resemblance between numerous insects of North America and of North 

 Europe is well known, and indicates the former existence of an intervening 

 continent. However, large numbers of insects in North America and in 

 Europe differ widely frum each other, those of the former having been 

 introduced from South America and those of the latter from the more 

 southern parts of the old world. The regions on the south of the equator 

 form three principal divisions : 1st, that of South America, where insect- 

 life is most abundant; 2nd, Australia and the numerous neighbouring 

 islands; 3rd., South Africa, where the insects are least numerous. 



The sixteen regions before mentioned are noticed as follows, omitting 

 in eaeh succeeding region the genera before enumerated: — 



1st. North Europe. 



Blatta Thamnotrizon Pacbytylus 



Periplaneta Decticus (Edipoda 



Loboptera Xiphidium Stenobothrus 



Gryllotalpa Meconema Epacromia 



Myrmecophila Locusta Stetheophyma 



Gryllus Phaneroptera Parapleurus 



Nemobius Acridium Gomphocerus 



Odontura Caloptenus Chrysochraon 



Gampsocleis Podisma Tettix 



Blatta is spread over all the regions, and the species of tropical 

 countries are numerous. Periplaneta is not a native of Europe and has not 

 been recorded as such in North Africa, nor in West Asia nor in North Asia, 

 but P. orientalis, the common cockroach or the " black beetle, establishes 

 itself in the houses of most English towns, and is domiciled in North 

 America. The species of Loboptera are few and small ; it has been recorded 

 also as a native of Hindostan. Gryllotalpa, the mole cricket, inhabits all the 



