Anatomy of the Male Genital Tube in Coleoptera. 495 



lobes. We have not examined one of these forms during copula- 

 tion, but it is most likely that the lateral lobes are used to keep 

 open the external orifice of the female. The internal sac is 

 undifferentiated, 



Laccohius ytenemis (PL XLIX fig. 45). 



This is a trilobe form. Median lobe chitinous on dorsal side, 

 membranous on ventral side whereon the median orifice is situate. 

 Lateral arms curved, surrounding median lobe. Basal -piece large, 

 membranous on dorsal side. Internal sac undifferentiated. 



Berosus signaticollis (PI. XLIX fig. 47). 



Median lobe thin, tubular, slightly curved and pointed at apex; 

 median orifice on ventral side of apex ; median foramen at base ; basal 

 edge continued into two curved median struts (m.s). Lateral lobes 

 large, consolidated into one piece on the ventral side, forming a 

 flattened trough into which the median lobe falls when at rest ; 

 point of articulation at base. Basal- piece large, forming a flattened 

 trough into which the lateral lobes fall when at rest, the distal 

 edge of the basal-piece being articulated to the middle of the ventral 

 part of the lateral lobes. Internal sac undifferentiated. 



In B. luridus the median lobe is slender and long, the 

 lateral lobes slender and long and quite free. Basal-piece 

 small and jointed to the lateral lobes in normal manner. 

 Internal sac undifferentiated. The profound difference 

 between these two otherwise allied species is of great 

 interest. 



Helophorus aquaticus. 



The median lobe is short, broad at base and bluntly pointed at 

 tip, where the median orifice is situate. Lateral lobes about same 

 length as median lobe, broad at base and bluntly pointed at apex. 

 Basal-piece longer than median lobe, shield-shaped, membranous on 

 dorsal, chitinous on ventral side. Internal sac undifferentiated. 



Dactylosternum suldeprcssum (PI. XLIX figs. 46, 46ri'-). 



Median lobe flattened, broad at base, pointed at apex, the dorsal 

 aspect being chitinous, the ventral membranous; the median orifice 

 towards the base on ventral aspect {mo). Lateral lobes meeting 

 together at base on ventral face, but wide apart on dorsal ; tapering 

 to a point at apex. Basal-piece small, chitinous all round, but narrow 

 on dorsal aspect, and extending basally on ventral side, there some- 

 what shield-shaped. Internal sac undift'erentiated. 



LL 2 



