216 Dr. David Sharp's Studies in Rhynchophora. 



brane with the body of the median lobe ; this intervening 

 membrane has been called by Mnir and myself first con- 

 necting membrane, but I here call it the second. This 

 lies within the tegminal layer, and is, in fact, a continua- 

 tion turning apicad thereof. It may be called the median 

 lobe layer. This layer is mentioned by Niisslin, who calls 

 it " Penisrohr," but he does not mention that it is con- 

 tinuous with the other layer, being an invagination thereof, 

 the tegmen being chitinised at or near the line of invagina- 

 tion. It must not be supposed that this point can be at 

 once settled by a slight examination ; for the doubling- 

 is usually complex, and accompanied by creases, as the 

 folding of the dorsal pare of the circumference may not be 

 at the same transverse line as the ventral folding, and may 

 be accompanied by a tuck or overlap. Moreover, this part 

 of the tube is the subject of considerable variation in 

 length according to whether the tegmen is drawn back 

 or pushed forwards, or the median lobe extended ; this 

 membrane is often very crumpled up. Our fig. 2 shows it in 

 an imaginary simple form, and it can in some forms, such 

 as Cionus, be actually extended into something like that.* 



This intervening membranous area — im2 — is really 

 common to the tegminal layer and to the median lobe 

 layer ; in repose it is crumpled up under the protection of 

 the tegmen, but when the median lobe is extended as in 

 fig. 4 the crumpling disappears. 



The median lobe is called by Lindeman the " Kcirper," 

 by Hopkins the " stem," by VerhoefT. and Niisslin the 

 " penis." It differs so much in form that it is difficult to 

 give a general description of it ; for our present purpose 

 we may merely say that in some forms (Naupactus sitl- 

 phurifer, Erythrapion, etc.) it is a long slender hard tube, 

 while in other cases it is more or less membranous along 

 the dorsal surface except at the sides, and this form, which 

 is very common, is shown in our fig. 3, and is well exhibited 

 by Hopkins' plate xi of the " stems " of Pissodes, though 

 his figures do not convey any indication of the fact that 

 this trough-like structure is really a tube, the sides of the 

 trough being connected by membrane. 



Whatever the shape of the median lobe it always pos- 

 sesses in Rhynchophora basally a pair of projections which 



: My daughter prepared for me a scries of drawings to illustrate 

 the elongation of the tube in ( 'ionusi bul as a whole plate would be re- 

 quired for it, publication must be deferred to a more favourable time, 



