10 BUTELIN^. 



than the secondary and later-developed intermediate ones, which 

 often break up, so that they may become partly duplicated or may 

 be scattered irregularly over the interprimary spaces, as in most 

 species of Adoretus. 



The spaces lying between the lines or grooves are called the 

 elytral intervals, and they, like the lines, are counted consecutively 

 from the suture outwards. The second interval from the suture 

 (frequently very broad and sometimes more or less completely 

 divided along the middle) is called the subsutural one. In order 

 that parts not really corresponding may not be confused by being 

 similarly numbered, it is important to distinguish between the 

 primary and interprimary spaces. This can alwavs be done by 

 remembering that the humeral callus (or shoulder-prominence) 

 is always just beyond the third primary costa, and that when 

 there are more than five intervals between it and the suture 

 (i. e. dorsal intervals) the 2nd and 3rd are derived from the 

 subdivision of the 2nd, and the 5th and 6th from that of the 

 4th primary intervals. 



Abdomen, The abdomen consists beneath of six visible seg- 

 ments, the first almost covered by the coxae and only slightly 

 exposed in the middle and at the sides. The first five segments 

 are capable of little or no separate movement, but between the 

 5th and 6th there is a wide flexible membrane, allowing free 

 play to the terminal segment. This segment may be large or 

 very small. In the female it is generally fairly large and its 

 posterior edge coincides with that of the last dorsal segment 

 (pygidium). The latter is usually large and completely exposed, 

 and a part of the preceding segment (propygidium) is often 

 exposed also. 



Genitaiia. In distinguishing the often closely similar species 

 here dealt with I have made considerable use of the genitalia of 

 the males, which in these insects can be removed and mounted 

 with little difficulty. The abdomen can with care be detached 

 in the dry state by pressure exerted beneath the elytra and can be 

 re-attached after the removal of its contents, a process which will 

 incidentally have the effect of reducing the risk of the destruction 

 of the specimen from subsequent chemical changes. The highly 

 chitinous sedeagus, when separated, should he fixed to a card strip 

 in such a way that it can be easily seen from every side. For 

 diagnostic purposes the rigid external sheath alone is usually 

 regarded, and the outline figures accompanying this work represent 

 that part only. Within the tubular sheath is the eversible sac, with 

 its generally complicated armature of spines, which may be found 

 extruded to a greater or less extent. Being a soft structure this 

 has no fixed outline and must be carefully left out of account 

 when comparisons are made. The highly chitinised sheath may 

 consist of a single tubular piece terminating in a kind of spout 

 of varying form, as in the genus Adoretus and certain groups of 

 Anomala, the orifice being on the dorsal side in the former and 

 the ventral side in the latter, but generally terminates in a pair of 



