March, 1920.] ShARP : STUDIES IX RhYXCHOPHORA. 75 



process; ventrally opposite to the median orifice is a membranous 

 bulge, d. If the median orifice be looked at as perpendicularly as 

 possible, it presents somewhat the appearance shown in fig. 4, which 

 shows a central chitin sclerite, c, and a median one, ta.; the latter 

 varies in appearance according to whether the sac is greatly retracted. 

 When the sac is extended it is found to be a bladder-like structure 

 with a lobe at its base ; this lobe consists of very complex hard pieces 

 partially shown in fig. 6, and through it runs the ejaculatory duct, ej., 

 opening on a spot fo., in the middle of this transfer apparatus; this 

 spot is the functional orifice where the sperm leaves the male struc- 

 ture for transference to the female. The extreme hardness and the 

 very complex shape of this transfer apparatus is unusual in the Cur- 

 culionids; but in the Tomicidse division of the Scolytidse there exist 

 very remarkable analogous formations, the " Auf satz " of Lindeman, 

 which I anticipate, when carefully examined to find the ejaculatory 

 duct, will also be found to bear the functional orifice. 



The position of this transfer apparatus at the base of the main 

 division, is., of the sac is also remarkable, as it is usually closely con- 

 nected with the wall of the main sac, and placed more or less at its 

 apex. 



The shape and nature of the transfer apparatus differs greatly in 

 the various forms of Rhyncophora, so that it will be difficult to gen- 

 eralize it for the purpose of definition of the great groups, but it will 

 be found very important in the case of definition of genera and tribes. 



Much mystery at present surrounds the male genitalia, which is 

 a sign of our ignorance. We say that as regards the great modi- 

 fications of the outer skeleton of an insect that they are " adapta- 

 tions." But no one so far as I am aware has endeavored to account 

 for the great diversities we find in the male organs. If they are the 

 results of "adaptations," what is the nature of these? 



The first idea that suggests itself is that there will be found to be 

 a correlation between male and female peculiarities, and I believe 

 that this will prove to be the case to a considerable extent. Unfor- 

 tunately we know but little of the female structures in Coleoptera. 

 In 1847 Stein published a very valuable work on the subject. "Die 

 weibliche Geschlectsorgane der Kafer," Berlin, and this remains the 

 only general work on the subject, but deals with only 3 or 4 Rhynco- 

 phora; Niisslin has since given up particulars of the structure of 15 



