342 NEOTROPICAL PSELAPHIDAE 



develops, the terminal cone is pulled basad so that it becomes obliquely set 

 within the apex of the sulcus. 



Several lines of development are possible: 



a. The main line would appear to include Apharus (with the sulcus 

 limited to the apical half), Hamotus s.s. (with the sulcus gradually lengthening, 

 but varying from short in which only the apical two-thirds of the segment are 

 sulcate, through a sulcus four-fifths segmental length, to entire in which the 

 sulcus divides the oblique basal margin and therefore radically alters the in- 

 ternal face since the basal margin is now continuous with the sulcal margin) , 

 Hamotoides (in which the tendency is for an entire sulcus of narrowing width). 

 At this point there appears to be a basic divergence in length-width ratio of 

 the segment: 



b. The fourth palpomere becomes very wide in proportion to its length, 

 as in Pseudohamotus with a very narrow, entire sulcus and a semicircular 

 outline. 



c. The fourth palpomere becomes very narrow in proportion to its 

 length, also with a narrowing of the entire sulcus: Hamotocellus, Cercoceroides, 

 Cercoceropsis. 



d. An aberrant line shows the palpal sulcus narrowed to striaform pro- 

 portions, and the distal palpomere becoming very narrow apically: Pselapho- 

 compsus, Cercocerulus. 



e. Another line would seem to diverge from Ba, in which the third 

 palpomere is spherical, and the simply ovoidal fourth palpomere is entirely 

 sulcate. The base of this segment is simple, and the sulcus is broad and fusiform. 

 Such a condition is approached by Aploderina. 



This system is but one of many possible. It should be integrated with the 

 tergite ratio, cephalic sutures, and sternal foveae as well as the pronotal sulcus 

 and elytral striae-costae complex. 



Of these structural criteria I should regard the sternal foveae, and espe- 

 cially the male copulatory apparatus as basic. These require prepared slides 

 and are being studied at the present time. 



