20 

 be patches of parallel ridges. Even though these have been 



called stridulatory, I have found no statement about the 



sound produced. They appear only on males in some species 



and on both sexes in others. The exact function of these 



structures is unknown. 



Representative species' antennae are illustrated on a 

 single plate for ease in comparison (Fig. 6) . If a species 

 antenna is not illustrated, a reference is given to the 

 antenna that is most similar: "(similar to Fig. X)", where 

 "X" is the figure number. 



The shape and proportions of the maxillary and labial 

 palp terminal segments are important for species 

 distinctions. These are illustrated on a single plate 

 (Fig. 7) for ease in comparing shapes and proportions. 

 This plate illustrates the palpi of representative species 

 to show the basic forms. The descriptions of species with 

 similar palpi have the statement "(similar to Fig. X)," 

 which refers to the figure "X" that is most similar to that 

 seen in the species being discussed. 



The "triangular mentum" is a characteristic of 

 Ischyrus. The "triangle" is a sunken area of the mentum 

 surrounded by a ridge (Fig. 8) . The triangular sunken area 

 is the mental plate. The ridge surrounding the plate is 

 the mental ridge; it is often extended forward at the 

 middle as a sharp divider between the labial palps. This 

 projection is called the medial ridge extension. As with 

 palp terminal segments, representative menta are 



