of the male genital tube in Coleoptera. 225 



long flagellum. At a later stage the median lobe is differ- 

 entiated, but the basal portion of the internal sac is not 

 withdrawn into the short median lobe until the insect is 

 mature. The median strut arises as an invagination at the 

 base of the median lobe. At first both the median and 

 tegminal struts are simple, tubular invaginations, but 

 at a later stage the former becomes dilated at the apex, and 

 the latter broad and thin. 



Comparative Morphology. 



If we examine the abdomen of a generalised trilobe 

 coleopteron nine or even ten tergites and nine sternites 

 can be easily discerned (in Enarsus bahewelli there is a 

 distinct tenth sternite lying between the anus and the 

 aedeagus). In the Dermestid figured * there are nine 

 complete abdominal segments, the anus opening on a small 

 membranous tube below the ninth tergite, the aedeagus 

 lying between the anus and the ninth sternite. The ninth 

 segment forms a complete ring, and is prolonged into the 

 abdomen as a strut on the ventral asjiect. In Rhyncho- 

 phorus ferrugineus only eight abdominal segments can be 

 traced; the eighth tergite is large, boatshaped, deeply 

 cleft at the base and slightly so at the apex, with the eighth 

 spiracle on the pleural area ; the eighth sternite is small and 

 lies across the ventral aspect of the eighth tergite, and 

 together they form a tube through which the aedeagus 

 plays ; the anus lies beneath the eighth tergite, between the 

 eighth tergite and the aedeagus. The cloaca so formed is 

 closed by the meeting of the posterior edges of the seventh 

 tergite and seventh sternite. In Rhabdocnemis <>h.^uir</ 

 (Boisd.) a similar condition prevails. In both these forms 

 the connecting membrane is chitinised and forms a pseudo- 

 tegmen; in Rhynchophorus there is no spiculum. In 

 Acantholophus and Ithycerus the cloaca is closed by the 

 meeting together of the posterior edges of the eighth tergite 

 and seventh sternite, the eighth sternite is small and, 

 together with the eighth tergite, forms a tube through which 

 the aedeagus plays, In the former there is a large spiculum 

 arising some distance from the base of the connecting 

 membrane, in the latter there is a distinct spiculum and 

 also a strut from the basal edge of the eighth sternite; the 



* This is a common species in Honolulu, but I have no name for 

 it at present, and no specimens in England. 



TMNS. ENT. SOO. LO^D. 1918.— FA^T.S I, II. (DEC.) Q, 



