NO. 3oG8 MELANOTUS — QUATE AND THOMPSON 23 



Lectotype of scrobicollis: Male, labelled with pink circle "Middle 

 States" (MCZ). Third specimen in type series selected as lectotype 

 by authors in 1962. First specimen with broken antennae and second 

 specimen, apparently male, doubtfully referred to this species. 



Type of texanus: Female, "Texas, Jansen Coll. ex Candeze 1903, 

 130," (BMNH). 



Distribution. — Holarctic. Southeastern Canada, eastern U.S. 

 west to Utah, Arizona, southern California, Mexico. 



Arizona: Coconino, Pima; June, July. California: "S. Cal." Colorado: 

 Larimer, "Waldo Canon"; June, July. Illinois: McHenry; May. Maine: 

 Penobscot; June, July. Massachusetts: Suffolk; May. Michigan: Alpena, 

 Crawford, Marquette, Oakland; June, July. Minnesota: St. Louis. New 

 Hampshire: Carroll, Cheshire, Coos; April, August. New Mexico: San Miguel. 

 New York: Cattaraugus, Cortland, Erie, Essex, Niagara, Oswego, Tompkins, 

 Warren; March, September. North Carolina: Wake; June. Ohio: Summit; 

 May. Pennsylvania: Carbon; June. Rhode Island: Washington; August. 

 Utah: Juab, Utah; January, July. Wisconsin: Dodge, Milwaukee; May, July. 

 Nova Scotia: Bridgetown; July. Ontario: Prince Edward; May. Quebec: 

 Mt. St. Hilaire, Regaud, Deparquest, Hull, Aylmer, Hudson; May, July. Mex- 

 ico: El Salto Diego, June. 



With its large size and small second and third antennal segments, 

 the male of castanipes is not difficult to recognize; it is easily sepa- 

 rable from ignobilis by the shape of the flagellar segments. The 

 females are more difficult to identify, since the third antennal seg- 

 ment is larger and more nearly intermediate between the second and 

 fourth, which makes it similar to spadix or similis. The weakened 

 frontal margin, when viewed from directly m front, is the most useful 

 external character for separating castanipes, but in doubtful cases 

 only the dissected genitalia will provide a reliable answer. 



M. castanipes is a widely distributed and variable species. Large 

 series from throughout its range might show it divides mto subspecies, 

 but, from our rather limited material, we can only point out the pat- 

 tern of variation we observe without applying names to any of the 

 variants. Throughout the species there is sexual dimorphism with 

 the females larger, the edges of the pronotum less flattened laterally, 

 the frontal margin less jutting, and the third antennal segment longer. 

 Specimens from the eastern United States are observably different 

 from those in the Southwest and the Great Plains. The western 

 specimens are smaller (male average elytron length is 10.7 mm com- 

 pared to overall average elytron length of 11.2 mm), and the pronotum 

 is more strongly flattened laterally and often more strongly divergent 

 posteriorly. The most conspicuous variation of the western speci- 

 mens is the thin, jutting frontal margm which often contrasts sharply 

 with the flattened or rounded, obsolescent margin in eastern specimens. 



