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DELPHACIDiE. 



The British Delphacidae number more than fifty 

 species, many of which are minute, and to the casual 

 observer show similarities one to the other, both in 

 form and in colour. In a general manner they may be 

 separated from other subfamilies by the forms of their 

 antennae, by the ocelli being placed on the cheeks, and 

 by a curious leaf-like spur attached to the lower part of 

 the hind tibiae. 



Dr. Fieber, with great sagacity, studied the varying 

 forms of the styles and adjuncts to the pygofers of 

 different species, and his observations go far to show 

 that these characters are sufficiently permanent to 

 allow of specific discrimination. Mr. J. Scott and 

 Mr. J. Edwards think, indeed, that to these general 

 characters must be the final appeal in difficult diagnoses. 

 These styloid appendages in the males act chiefly as 

 claspers, and they may be regarded as secondary sexual 

 organs. Variation in these secondary characters has 

 been generally ascribed almost exclusively to the 

 males ; but in the Delphacidae, Deltocephalidae, and 

 other subfamilies of Cicadidse, modification occurs in the 

 females ; as may be seen in the different forms of their 

 saw-like ovipositors and sheaths. 



John Hunter first designated as " secondary sexual 

 characters," the wattles of the turkey, the comb of our 

 poultry-cock, and the like, as being mere appendages, 

 and not subservient to the act of reproduction. 

 Appositely, Mr. Darwin has stated his conviction of the 

 importance of a rule, which he says is capable of large 

 generalization, that parts extravagantly, that is extra- 

 ordinarily, developed in animals are highly variable ; 

 and also that the species of a large genus which 

 present any variation, invariably present a larger average 

 number of them than do the species of a small genus. 

 Geoff. St. Hilaire appears also to decide that the more 

 an organ differs in the various species of a group, the 

 more subject it is to anomalies in individuals. From 



