406 DR. F. LEFTHNER ON THE ODONTOLABINI. 



mandibles step by step from one moult to another, the above conclusion would be 

 positively demonstrated. 



I spared no trouble to seek for examples among these insects in which the full-grown 

 male possesses enormously developed mandibles like the Lucanidae, which are nor- 

 mally developed in the female. As Nature works on parallel lines, I found my views 

 confirmed in an Australian cricket {Anostostoma australaske, Gray), in which (as shown in 

 the accompanying woodcut, fig. 5, p. 405) the sexually-mature male has enormously 

 long and strongly curved mandibles (nos. 1, 2). There is an apical cluster of teeth, and 

 a broad obtuse tooth, used for masticating, at the base (no. 2, side view). 



In the female the mandibles are small, and are set with serrated biting teeth on the 

 inner side (like a priodont form, cf. no. 3). The very young larva of the male, the 

 sex of which can be recognized at once by the absence of an ovipositor, begins at the 

 same stage as the female in the development of the mandibles (no. 4). 



The enormous mandibles of the male are apparently here also designed for grasping 

 the female, and have been gradually developed in this manner by the survival of the 

 fittest. 



As the Orthoptera continue to take nourishment constantly throughout the whole 

 course of their lives until their death, which soon follows coition, a total change 

 of function in the mandibles, as in the Lucanidse (from the mandibles of the larva 

 to the mandibles of the imago), is impossible ; and when the mandibles are needed 

 to fulfil an additional function, their increase in length necessitates the lengthening 

 of the entire buccal apparatus (the labrum, maxilla, &c.). Only in this strange and 

 paradoxical manner could the two objects of the mandibles be fulfilled without inter- 

 fering with one another. 



(6) Divergence of Species in the Odontolalini. 



{Investigations into the Agreement and Difference of the Morphological Characters, as 

 a Contrihution to the Knowledge of their Mutual Belations.) 

 In the previous Chapter we treated of the variations which occur within the narrow 

 limits of a single species, and must now recapitulate our results, in order to study 

 the agreements or differences of the known species. A mere glance at one of our 

 Plates will suflfice to show any entomologist that, in comparison with the consider- 

 able variations which occur in a single species, the difi'erences which separate one 

 species from another are often very slight — so slight that in our comparative 

 descriptions wo are obliged constantly to use such expressions as " a little more 

 or less," " very similar," " very closely allied," &c. ; while some differences are so slight 

 that, although perceptible to the eye, they cannot be expressed in words. Our figures, 

 like our descriptions, cannot attain the acme of perfection, an absolute facsimile of a 

 specimen being practically unattainable. 



