Miscellaneous. 163 



In Gryllotalpa the length of all the hind tarsal joints taken to- 

 gether seldom exceeds half the width of the pronotum, while they 

 equal its whole width in Sccqiteriscus. 



The hind tarsal claws of Scapteriscus are clothed with short hairs 

 nearly to the tip ; those of Gryllotalpa have hairs only at the base. 



The tcgmina of Scapteriscus, with but few exceptions, cover, when 

 at rest, two-thirds of the abdomen ; in Gryllotalpa they seldom con- 

 ceal more than one-half of the abdomen. 



The nervures of the middle field of the tegmina in the females of 

 Gryllotalpa are distant and rather irregular, somewhat resembling 

 those of the males ; in Scapteriscus they are approximate, regular, 

 and straight. 



The anal cerci are longer than the pronotum in Gryllotalpa ; 

 shorter in Scapteriscus. 



Finally, the ninth and, sometimes, the eighth abdominal segments 

 are furnished above, in Gryllotalpa, with two transverse lateral rows 

 of long hairs directed inward, as if to keep the long folded wings in 

 place ; these are absent from Scapteriscus, where the wings are 

 equally long and similarly folded. 



Only one species of Scapteriscus has been found without the limits 

 of South and Central America, and that (occurring in a single in- 

 stance in Europe) must undoubtedly be considered an emigrant from 

 the same warm regions ; the members of the genus Gryllotalpa, on 

 the contrary, are found throughout the whole world, not excluding 

 Central and South America. 



Comparing these two genera with their nearest allies, Tridactylus, 

 Cylindrodes, &c, we find great and striking differences — differences 

 which are extraordinary compared with those which divide Scapte- 

 riscus and Gryllotalpa : the comparatively simple fore tibia? and the 

 abnormal appendages which supplant the hind tarsi in Tridactylus, 

 the abbreviated legs fitting into cavities in the body, and the absence 

 of articulated appendages at the extremity of the abdomen, in Cylin- 

 drodes — these characteristics are far more important than the sexual 

 sculpture of the abdomen, the ultimate neuration of the tegmina, 

 the length of the legs, the contour of the trochanters, or the digita- 

 tion of the tibia?, which separate Scapteriscus and Gryllotalpa. 



The facts cited above present two features which bear upon the 

 question of the origin of species. 



First : these little mole-crickets, so unique in their structure as 

 to be widely separated from their nearest allies, are spread uniformly 

 over the whole surface of the globe ; but few species occur in any 

 one place, and at least one is found in every temperate or hot region. 



Now, if species originate or change from physical causes, or by 

 " Natural Selection," why is it that under every physical condition 

 and surrounded by every variety of antagonism possible in their 

 habitat, this same unique structural form has sprung up all over the 

 globe ? 



Again, how can such theories account for another feature (com- 

 mon, indeed, to all natural groups), that it is not one striking cha- 

 racteristic which separates Scapteriscus and Gryllotalpa, and which 



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