612 Mr. D. Sharp and Mr. F. Muir on the Comparative 
keep open certain spaces between the sac and the wall of 
the female tubes. Observations on the positions taken up 
by the sacs within the vagina during copulation are greatly 
to be desired. 
The pressure necessary to drive the viscid fluid from the 
testes through the long slender ducts must be very 
great, and the thick coating of muscles surrounding the 
ducts serves to this end. The pressure behind such a 
flagellum as is found in Baryrhynchus miles, where it is 
12 mm. long, and ‘006 mm. in outside diameter toward the 
tips, must be well directed and considerable. 
It is worthy of note that the armature of the sac of 
Donacia sericea, etc., recalls the parts of the aedeagus, 
there being a median lobe, through which the ejaculatory 
duct passes, and opens on its apex, and a pair of lateral 
lobes. There is, as it were, a secondary aedeagus within 
the aedeagus. To find out the action of these pieces 
during copulation would be of interest. 
Whether the lateral lobes in such a trilobe form as 
Ceratognathus pass info the vagina and then diverge and 
thus hold the female, we are unable to say. In Stenus 
speculator (fig. 232) the lateral lobes are placed along the 
outside and hold the female. In Coccinellidae they are 
placed on the outside of the female venter, and appear 
to have no hold. In some of the Cistelidae the hind 
body-segment is developed into claspers to retain the 
female. In Malthodes (fig. 233) and Malthinus (fig. 235) 
the last abdominal segment is used as a clasper, and 
the last segments of the females have depressions into 
which the ends of the claspers fit to give them a firmer 
hold. In Telephorus and Rhagonycha the edge of the 
vagina is held between the tongue of the tegmen (fig. 236a) 
and the median lobe. In these species the aedeagus takes 
nearly a half turn during copulation (fig. 238). The 
twisting of the aedeagus during copulation is common to 
many forms, and in some it makes a complete half turn. 
This is the case in the Caraboid type. In such an one as 
Dytiscus punctulatus the aedeagus, when at rest and drawn 
into the abdomen, lies on its side, and when thrust out the 
median lobe curves downwards, but its true orientation is 
with the median lobe curved upward as we figure it (fig. 37). 
It is probable that in many forms the female does not 
play an entirely passive part in the act of copulation ; as 
to which see the remark made under Cyphon. 
