212 Dr. David Sharp's Studies in Rhynchophora. 



is usually membranous in the middle so as to be two distinct 

 plates, but sometimes it is entire, arid this is a character 

 of much taxonomic importance. This last ventral may be 

 called the eighth, or the true last ventral, so that in the 

 ordinary course of counting, we pass at once from five to 

 eight. The two missing sternites are, as explained above, 

 really to be found at the base. Lindeman did not recog- 

 nise this, and started the idea that one of these apparently 

 missing plates was to be found in the genital tube in the 

 form of the spiculum gastrale. If that view be adopted, we 

 have really nine abdominal sternites and only eight tergites. 



One of the complications in counting the abdominal 

 segments is found in the case of the family Belidae, where 

 there are superficially visible only seven dorsal plates. 

 This, however, is due not to any real deficiency, but 

 arises from the eighth segment being of very peculiar 

 form, and telescoped into the segment preceding it. 



In the Australian Belidae the concealed terminal seg- 

 ment can be easily pushed out, and is then found to be 

 of very extraordinary shape, the dorsal plate being bent 

 so as to have as great a surface on the ventral aspect as 

 on the dorsal, and thus there is the simulation of an addi- 

 tional sternite. In the North American Ithycerus (which 

 is only a subfamily of Belidae) the terminal segment- is 

 constructed as in Belus, but is exposed and not telescoped 

 into the preceding segment. In this case there were, 

 therefore, considered to be six (instead of the usual five) 

 externally visible ventral plates ; the error was, however, 

 corrected by Dr. G. H. Horn many years ago (cf. Leconte, 

 " Rhynch. of North America," p. 121). 



The last dorsal is not of so great taxonomical import- 

 ance as the last ventral; but it is subject to considerable 

 modifications, one of which deceived Kolbe into describing 

 it as the aedeagus. This error has been pointed out and 

 corrected by Verhoeff. It is one that may be easily made 

 in that particular case (Rhynchophorus), and it has unfor- 

 tunately been copied in Packard's text-book; but it may 

 be mentioned as showing the necessity of examining the 

 tip of the abdomen when we are studying the genitalia. 



The Spiculum Gastrale. 



('lose together, at the tip of the abdomen, we find to 

 investigate the ventral and dorsal plates of the last seg- 

 ment, tin- termination of the alimentary canal, the junction 



