THE AUCHENORRHYNCHOUS HOMOPTERA. 119 



the segments) or consists of from two to six segments ivhich are 

 provided ivitk a few simple sensory organs, consisting of fairly 

 deep small pits, which have a sensory-spike projecting from 

 within. I have never found traces of sensory organs on the 

 remainder of the thin bristle-like segment, except perhaps in the 

 male of Idiocerus, in which the apical part of the flagellum forms 

 a large flat oval plate (pi. i. f. 6), on which scattered points 

 appear, which are perhaps peculiar, extremely small sensory 

 organs, but of the nature of which I can say nothing, since my 

 strongest magnifying power (600 times) was quite insufficient. 

 In Tettigonia ferraginea (f. 5) the flagellum is very long and fine, 

 except its somewhat thicker but still proportionately very slender 

 sensory basal part (f. 5 a), which clearly consists of five seg- 

 ments, of which the three middle are the shortest, and the last — 

 probably formed by the fusion of two segments — long. The 

 remainder of the flagellum consists of a large number of seg- 

 ments, of which the proximal ones are short, the others longer ; 

 each one, however, is somewhat irregularly superficially divided 

 into several extremely short segments {false segmentation). The 

 last part of the flagellum is very thin, and in it every trace of 

 segmentation has disappeared. In Idiocerus populi S (f. 6) the 

 sensory basal part of the flagellum is of the thickness of the 

 same part in Tettigonia, and consists of six segments ; the part 

 between the basal segment and the recently mentioned " Palette " 

 is not twice so long as the sensory part, and consists of eighteen 

 to nineteen rather strong and to some extent regular segments, 

 which are not again divided as in Tettigonia ferraginea. In 

 Ledra aurita (f. 7) the basal part is very similar to that in 

 Tettigonia, but consists, however, of only three segments, of 

 which the last is very long. The apical section is shorter and 

 thicker than in Tettigonia, but, however, tapers, and is divided 

 from the base to about the middle into numerous small segments, 

 while the remainder is quite without segmentation. In Ulopa 

 reticulata (f. 8) the sensory part is extraordinarily thick through- 

 out, and consists of two segments only ; but the apical one is 

 very long, and certainly corresponds with more than one in the 

 last mentioned genera ; the rest of the flagellum is also thick, 

 though it tapers towards the apex ; it is divided into sixteen 

 normal segments, which increase in length towards the apex. In 

 Centrotus cornutus (f. 9) the sensory portion is fairly thick, 

 gradually tapering and badly separated from the distal part ; its 

 segmentation is not distinct, and is rendered more indistinct 

 from irregular transverse stripes ; the rest of the flagellum is 

 coarse, consisting of numerous short irregular segments. In 

 Mthalion reticulatum (f. 10) the flagellum is formed very similarly 

 to that of Centrotus ; the sensory section is, however, separated 

 more distinctly from the rest, which is proportionately somewhat 

 thinner. In Membracis tectigera the sensory parts are formed as 



l2 



