terminal segment in some male Hemiptera. 407 



segment in the male is very retractile, and in the con- 

 dition of repose is drawn so completely into the hody 

 that when the insect is looked at from above or below 

 the segment appears to be entirely absent, but looked at 

 from behind all the parts of the structure are displayed, 

 and present a very remarkable appearance ; the segment 

 may be easily withdrawn by extension from the protection 

 of the body, and it is then seen that the remarkable 

 processes of the terminal chamber are really greatly 

 exposed. In the middle there is seen a structure pre- 

 senting a concavity somewhat like an oyster- or scallop- 

 shell in shape, with raised margins : this is a portion of 

 the rectal-cauda ; on each side posteriorly the angles of 

 the segment are flexed upwards and dilated, and are 

 remarkably irregular in form ; above them the superior 

 angles of the chamber project backwards, and form on 

 each side a process somewhat similar to the posterior 

 angles ; there is no inferior process behind the rectal- 

 cauda ; the lateral appendages are concealed in the large 

 irregularly-shaped fissure existing between the superior 

 and inferior angles, as above described, and the tip of 

 the appendage just comes into contact with the peculiarly 

 raised black margin of the reflexed inferior angle : on 

 the middle of the dorsal part of the segment there is 

 seen projecting backwards a process which, seen from 

 above, looks very like the rectal-cauda of the Tesserato- 

 mince, and which, occupying as it does exactly the same 

 position, would naturally be supposed to be the homo- 

 logue of that part : but this is not so ; this projection is 

 a portion of the anterior chamber projecting backwards, 

 and in all probability is homologous with the corrugated 

 membrane I have described as existing at the base of 

 the rectal-cauda in Eusthcnes eurytus. 



The rectal-cauda examined in detail is of remarkable 

 structure ; its basal part is placed under the process just 

 mentioned, and is quite delicate and membranous, but 

 immediately beyond this its outer aspect is developed 

 into the peculiar shell-like structure I have already 

 mentioned ; beyond this shell-like piece there is a narrow 

 chitinous strip, deflexed so as to be placed almost at 

 right angles to the preceding part of the cauda, and the 

 orifice of this cauda is directed quite downwards, and is 

 surrounded by a protruding pale membrane. 



The membranous basal portion of the rectal-cauda 



