590 



MESSRS. BATESON AND BRINOLEY ON [Nov. 15, 



also in other ways large individuals, while the males with small 

 horns are small individuals. But though there is some correlation 

 between absolute size and the degree to which the horns are devel- 

 oped, our measurements have shown that this correlation is not 

 perfect. It is of course clear that the ratio of length of the horns 

 to that of the body is greater in the high males than in the low. 



Baron von Hiigel gave us some interesting particulars as to the 

 natural history of these beetles. They were collected in the height 

 of the breeding-season, perhaps the greater number being found 

 coupled. It was noticed that large males were often attached to 



Fig. 3. 



r./A 



Cp.h 



m 



Diagrams oi Xylotrwpcs gideon, (^ , seen from side. Legs not shown. 



I. High male. II. Medium male. III. Low male. 



T.h., thoracic horn ; Cp.h., cephalic horn. 



small females and the reverse, but there appeared to be no regularity 

 in this. In view of the circumstance that there are scarcely any 

 observations as to the functions of the horns of beetles, the following 

 statements of Baron von Hiigel are especially noteworthy. He says 

 that the animals were caught by himself and by natives, and were 

 tied up with pieces of bast. "When they were brought home and 

 untied, the males immediately sought out the females, and seizing 

 them transversely, carried them about, held between the two horns, 

 with evident satisfaction. He tells us that this was observed again 

 and again, and was clearly a definite habit. The males with small 

 horns, though unable to lift the females, nevertheless made ludi- 

 crous efforts to do so. In answer to the question whether it was 

 observed that these small males did not succeed in obtaining females 



