Anatomy of the Male Genital T'uhe in Colcoptera. 595 



beautiful movement of a limited nature. In repose they are 

 brought near together, and their inner dorsal margins lie parallel 

 though separated by a good space. If a little pressure be applied 

 inside the aedeagns at the point where they meet dorsally, the two 

 lobes separate by a partial rotation and then disclose a broad orifice 

 such as we find to be the fixed position in Xylotrupes gideon. The 

 specimen is in very bad condition, but we mentioa it because we 

 have not observed a similar peculiarity in allied forms, though it 

 may not improbably be found to exist elsewhere in the higher 

 Dynastinae. The form and general proportions of the aedeagus are 

 similar to those of Oryctes boas. Some special experiments made 

 with that species show that the lateral lobes can be forced apart to 

 a considerable extent by pressure, but there is no rotation whatever, 

 and the parting is due to the elasticity of the ventral plate connecting 

 the lobes, 



Xylotrupes gideon (PI. XLVI figs. 26, 26a and 26b). 



Median lobe large, membranous, with chitinous ring at base for 

 support, prolonged into a pair of median struts, consolidated at their 

 base. Lateral lobes consolidated on dorsal and ventral side, short 

 forming a short ring or tube which projects on the ventral side as 

 two short, flattened and truncate points, which have a slightly out- 

 ward turn. Though the lobes are thus separated at their distal part, 

 they are united, in front of the free processes, to form a ring. Basal- 

 piece large, tambour-shape, constricted about the middle, with a 

 ventral plate (vp) which is only consolidated to the lateral lobes at 

 the corners (a)* Internal sac large with two large, strong, curved 

 spines about the middle. 



We have examined several specimens of this well-known insect ; 

 they come from different localities, and there is slight variation in 

 the aedeagus. 



Three males from Koberi (N. Guinea, Pratt), one of them the 

 fullest development of the species, the other two moderate, agree 

 closely except that the largely developed example has the distal 

 portion of the tambour more elongate, and the tusks of the lateral 

 lobes less abruptly turned backwards. 



A single specimen from " Australia " (old coll.), is of the broad, 

 robust variety of the species, with broad thoracic horn, and the forks 

 of the cephalic horn strongly developed ; it has the aedeagus much 

 as in the moderate Koberi form, but a little shorter and thicker, the 



* In fig. 26 the point (a) appears to overlap the lateral lobe : tliis 

 is not correct ; " a " only reaches the margin of the lateral lobe, and 

 is there conjoined with it, 



