Lucanidce of Japan. 335 



the way of variation which extends beyond what we 

 observe in many other insects. There are the sexual 

 differences of the family and little more, and Figulus 

 also follows in the same line, but has no external sexual 

 characters to speak of. We see, then, that the vigorous 

 forms of the family (Lucanus) have acquired a sexual 

 development which is not shared in by the smaller forms 

 (Figulus). 



The Lucanidce of Japan are all reared in decaying 

 trees, and the variation which occurs in the individuals 

 of their species relates chiefly to size, and can, I think, 

 only be traced to the feeding of their larvae. The larval 

 condition of insects is the stage of growth ; the period 

 from the egg to the pupa is the time when an insect 

 increases in size and weight, and it is certain that many 

 of the eggs deposited in summer will be laid on such 

 parts of decaying trees which are too hard, or perhaps 

 too rotten, for the larvae to thrive on. And even more 

 than this, they may be laid on trees of harder texture 

 or closer fibre than is essential for the highest develop- 

 ment of the larvae ; and many larvae of Lucanidce, as in 

 other insects, die simply of starvation at the first or at 

 another early stage. Small varieties of a Lucanus are 

 to me simply those forms which escape starvation, and 

 yet are emaciated by poverty of food, and each indi- 

 vidual increases in stature, in proportion to the nutri- 

 ment of its food, until it reaches the form maximus. A 

 familiar case to us all of the result of nutritious diet is 

 the queen bee, and last year Mr. Pryer gave us another 

 instance in drawing attention to Japan Papilios. 



Sometimes in a northern country we find insects 

 which have affinities in the tropics, and we see that the 

 northern forms are much larger than their southern 

 congeners. As an example, take Rhysodes. The Japan 

 species is half as large again as the Ceylon species, 

 because the first lives in beeches, elms, and oaks, while 

 the second feeds in the hard- wooded tropical trees, which 

 are, as I believe, less nourishing. (Trans. Ent Soc. 

 Lond., 1882, pp. 476 and 482). 



But we need not depart from the Lucanidce for an 

 example of this, as the Lucanidce themselves are rare in 

 the Ceylonese jungle, and many hundreds of specimens 

 can be collected in a summer day in Yezo, where 

 deciduous trees are the rule and not the exception. As 

 regards the Platycerus, it being of a small size, the 



