SYNOPSIS OF SPECIES OF LISTRUS 179 



Antennae notably stout; joints sixth to the ninth subequal in size and form; 

 fourth distinctly triangular and scarcely longer than wide; third rather 

 short, not twice as long as wide (male). More slender and subclavate 

 in the female 39. olympianus, n. sp. 



SALICIS GROUP. 



Central area of the pronotum not indentato-punctate, intervals flat; smaller 

 species, lustre aeneous ; antennae and legs clear rufous ; antennal joints 

 six to nine not elongate 40. occidens, n. sp. 



Central area of the pronotum densely indentato-punctate 1 



1. Antennae moderately stout and blackish in color; lustre dark, maculation 



well developed; fourth antennal joint triangular; fifth joint serrate and 

 about as wide as the ninth (male) ; pubescence of the fifth ventral seg- 

 ment scarcely modified in the male; antennae moderately dissimilar in 



the sexes 41. angulatus, n. sp. 



. Antennae rufous or ruf o-piceous in color, lustre more or less aeneous ; 



tibiae and tarsi more or less rufo-piceous 2 



2. Fourth antennal joint obconico-triangular ; fifth joint scarcely wider than 



the sixth; joints three to nine moderately elongate in the male; antennae 



moderately dissimilar in the sexes 42. salicis, n. sp. 



. Fourth antennal joint not strongly triangular; joints three, four and five 

 elongate, six, seven and eight less so; fifth not strongly serrate; antennae 



more slender in the female 43. niveicanthus, n. sp. 



Form smaller, apical joints of antennae darker iincticornis n. subsp. 



INTERRUPTUS GROUP. 



Interstitial spaces of the central area of the pronotal disk, flat and smooth ; 



spaces variable in width 1 



Interstitial spaces more or less indentate; surface more or less densely 



indentato-punctate 5 



1. Pubescence short, very sparse; maculation scarcely discernible; antennae 



slender, more or less rufo-piceous, fifth joint scarcely wider than the 



following two or three joints 44. amplicollis Casey 



. Pubescence longer and denser; maculation distinct . 2 



2. Lustre more or less aeneous; pubescence moderately long; antennae rufo- 



piceous 3 



. Lustre dark, bluish or greenish metallic; pubescence shorter 4 



3. Maculation consisting of rounded maculae on the elytra; fifth ventral of 



the male broadly and strongly sinuato-truncate at apex, flattened on the 

 disk and clothed with long erect and bristling hairs which become black 



in apical half 45. interruptus Lee. 



. Maculation consisting of three moderately wide fasciae, median and sub- 

 apical with irregular edges; fifth ventral clothed with brownish gray 

 hairs on the flattened area < 46. elegantulus, n. sp. 



4. Lustre with a dark steel-blue metallic reflection; legs and antennae black 



throughout ; pubescence very short, decumbent and coarse, a median and 

 subapical fascia with basal, post-basal and apical maculae, or with fasciae 



broken into maculae., 47. rotundicollis Casey 



. Lustre with a virido-aeneous- reflection; legs and antennae more or less 

 picescent, second joint paler; pubescence rather short, dark areas large, 

 two wide and straight transverse fasciae on the elytra behind the 



