v LAMELLICORNIA STAG-BEETLES 193 



provided with highly -developed stridulatoiy structures. No 

 auditory organ is known, unless the peculiar spiracles be 

 such. 



Fam. 2. Lucanidae (Stag-beetles). Labrum indistinct, fixed ; 

 mentum not excised ; antennae not curled in repose, with but little 

 coadaptation of the terminal joints ; the elytra, entirely cover the 

 dorsal surface of the abdomen. The Stag-beetles are well known 

 on account of the extraordinary development of the mandibles in 

 the male sex, these organs being in some cases nearly as long as 

 the whole of the rest of the Insect, and armed with projections 

 or teeth that give the Insects a most formidable appearance. So 

 far as we have been able to discover, these structures are put to 

 very little use, and in many cases are not capable of being of 

 service even as weapons of offence. The males are usually 

 very much larger than the females, and are remarkable on 

 account of the great variation in the stature of different indi- 

 viduals of the same species ; correlative with these distinctions 

 of individual size we find extreme differences in the development 

 of the head and mandibles. Moreover, the small male specimens 

 exhibit not merely reductions in the size of the mandibles, but also 

 show considerable differences in the form of these parts, due, 

 in some cases, apparently to the fact that only when a certain 



length of the mandible 

 is attained is there any 

 development of certain 

 of the minor projec- 

 tions : in other cases it 

 is not possible to adopt 

 this view, as the small 

 B mandibles bear as many 



FIG. 87.-Head M anaprothoraxofformsof the male of projections ES the large 



a stag-beetle ; Homoeoderns mellyl (Africa). A, forms do, Or even more. 



Large. B., intermediate, C, small forms. (From a T 



photograph by ROberthtir.) In each species these 



variations fall, in the 



majority of cases, into distinct states, so that entomologists describe 

 them as " forms," the largest developments being called teleodont, 

 the smallest priodont ; the terms mesodont and amphiodont being 

 applied to intermediate states. Leuthner, who has examined many 

 specimens, states that in Odontolabis sinensis, no intermediates 

 between the teleodont and mesodont forms occur, and as the 



VOL. VI 



