lyi.-;.] 27 



STUDIES IN HELOPHORINI. 



BY D. SHARP, M.A., F.R.S. 



2.— AN ACOOUNT OF THE AEDEAGUS. 



The description here given of the aedeagus is taken from 

 Meghelojjhorus a(p(aticns ; in its main features it applies also to the 

 other forms of the sub-family, as in this group there is much less 

 diversity than is the case in many sub-families of the Coleoptera. On 

 dissecting specimens it will be found that there is no external feature 

 by which the sexes can be distinguished ; there is a concealed internal 

 segment of large size, with dorsal and ventral plates differing little in 

 colour and texture from the other ventral plates, though not quite so 

 strongly chitinised. The dorsal plate — or tergite — is rather longer 

 and narrower than the sternite, and this is the case in each sex. 

 There is a spiracle between them. The aedeagus is quite small and 

 remarkably simple in structure ; of the trilobe form. Its basal sclerite 

 is very large, longer than the rest of the aedeagus ; it begins in front 

 as a rather small triangle or point, rapidly broadens, and in the middle 

 of its length extends over rather more than the half of the circumference 

 of the tube, the other portion of which is delicate transparent membrane, 

 the membranous portion being the dorsal aspect. This basal sclerite 

 is not very hard except near the line where it becomes membranous, 

 and the hard part connects with the base of the lateral lobe and a little 

 overlaps it ; in the middle, behind, the chitiuisation becomes feeble so 

 as to leave a broad, short triangular space in front of the base of the 

 lateral lobes, transparent. 



Tlie lateral lobes are elongate ; they are quite similar one to the 

 other, pointed at the extremity, with the outer margin slightly sinuous, 

 and (except for this sinuosity which is confined to a few species) almost 

 parallel- side externally ; the pointed tips are not hard, but rather 

 delicate even in perfectly mature specimens ; at the base on the ventral 

 aspect the two sclerites forming these lobes are contiguous, but almost 

 immediately diverge a little, and then, continuing backwards, leave an 

 almost parallel space between them for quite one-third of their length, 

 when they diverge more strongly, continuing thus to the tip, and leave 

 a broad space in which the median lobe is exposed, and their shape on 

 the dorsal aspect is the same as on the ventral. 



