DE. F. L£UTH>;EK ON THE ODONTOLABINI. 389 



a single species (0. alces). Taking this as a starting-point, I studied the species which 

 stand nearest to it morphologically, and thus gradually enlarged my horizon, until I 

 was at length enabled to examine the whole amount of material contained in tlie 

 principal European collections. I thus examined nearly 10,000 specimens of Lucanidse, 

 and about 1000 specimens of Passalidae (a group which was formerly erroneously 

 included in the Lucanidse), and investigated the constancy or inconstancy of their 

 morphological characters. 



The following are the conclusions at which I have arrived respecting the variability 

 which exists within the limits of a single species : — 



Although the male and female form a single whole, constituting one species, both 

 sexes vary, but in different directions. The male varies much more in size, shape, and 

 colour than the female, which remains more constant to the type, so that the females 

 even of distinct genera are very similar, and are frequently very difficult to separate 

 from one another, while their males are often very distinct. 



Female. The females are often remarkably different from the males, both in form 

 and size. They generally agree with them in colour; and in cases where they are 

 differently coloured, it is much more difficult to refer them correctly to the males. 

 Examples: Odontolahis stevensi (PI. XC. figs. 1-4), 0. rjazella ( = 0. Kcolor 6 , and 

 0. gazella 2 ) (PI. XCVT. figs. 10, 11). 



In Cyclommatus the females of the majority of the species are dark-coloured, and 

 are brown or metallic like the males ; but the females of C. mniszecM, Thoms., and 

 C. strigiceps, Westw., have bicolorous elytra. 



In Odontolabis brookeanus the colour of the elytra is variable (PI. XCV. figs. 16-18). 



In small specimens of 0. lacordairii (PI. XCIV. fig. 7) the red spots on the prothorax 

 are wanting, and the canthus round the eyes varies in width. 



Tlie form and size of the prosternal process is variable, and the number of spines on 

 the outer side of the front tibiae also varies. But the size of the tvfiole insect is the 

 most variable character. 



Male. The males of the same species vary much more than the females : — 



(1) In the total size. 



(2) l7i the size, form, and teeth of the mandibles (Cladognathini and Odontolabini). 



(3) In the number of apical lamellae of the antennce. In some cases this is an important 



family character, but in Lucanus cervus '■ these vary in form and size, and there 

 may be either 4, 5, or 6. 



(4) In the shape of the head. 



(a) Enormous development of the frontal ridge in Homoderus mellyi, Parry ^ and 



' Compare Abeille de Perrin, Auu. Soc. Ent. France (4) vii. p. 70 (1867). 



= Compare H. DejroUe, Ann. See. Ent. France (4) iv. p. 316, pi. iv. figs. 2, 2 a (1804) ; Parrj-, Trans. Ent. 

 Soc. Lond. (3) ii. pi. xi. fig. 6 (1864) ; and Westwood, op. cit. (3) i. p. 437, pi. xvi. figs. 7, 8 (1863). 



