BY E. W. FERGUSON. 697 



Section i. 

 Apical segment of abdomen with a median longitudinal 

 channel in the ^; no ventral vitta present. 



I regard the species comprised in this Section as constituting 

 but one group, although they fall into three subgroups, varying 

 in the characters utilised in the second Section for subdividing 

 into groups. 



Subgroup A. — Species with all the elytral interstices tuber- 

 culate; the intermediate tibiae simple. 



Subgroup B. — Species with the intermediate tibiae, in the ^, 

 will) a strong subapical notch. 



Subgroup C. — Species with the third and fifth interstices 

 c.jstiform, and the second and fourth neither tuberculate nor 

 costiform. 



The species of this Section have proved the most difficult to 

 define satisfactorily in regard to their specific characters and 

 range of variation. Tlie separation off of the second and third 

 Subgroups, still leaves a large number of species showing great 

 variation, and running, the one into the other, in a most bewil- 

 dering fashion. The confusion has not been lessened by the fact 

 that a number of the species have been proposed for single speci- 

 mens, many of which appear to be somewhat aberrant forms of 

 commoner species; and of which, in some instances, I have not 

 been able to procure an exactly identical specimen. 



A feature of importance, previously overlooked by me, in the 

 separation of the species, lies in the structure of the anterior 

 tarsi. In S. Adelaides, for example, the three basal joints are 

 subequal in width, each joint being symmetrical; whereas, in »?. 

 tristis, the third joint, and, to a less extent, the second, are asym- 

 metrical, the inner portion being more expanded tlian the outer. 

 My failure to note the two types of i;arsal structure has led, in 

 a former publication, to a misidentification of iS. sordidus Macl. 

 The type, fortunately, has the three basal joints of the anterior 

 tarsi remaining on one side; these are as in *S'. tristis, and I have 

 no doubt now that S. sordidus is the male of S. acuminatus. 



The species with simple tarsi show a remarkable gradation in 

 the size of the elytral tubercles, and, to a less extent, in the size 



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