36 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



Scott, Union, Vermilion, Washington; April, July. Indiana: Spencer, Tippe- 

 canoe; June. Iowa: Henry, Story; June, August. Kansas: Chautaugua, 

 Cowley, Douglas, Miami, Montgomery, Riley; May, June. Kentucky: Jeffer- 

 son; June. Louisiana: Madison; June. Maryland: Anne Arundel, Washing- 

 ton; June, July. Mississippi: George, Greene; April, May. Montana: Calla- 

 way, Clinton, Jefferson, Lawrence, St. Louis, Webster; April, July. Nebraska: 

 Cass, Dakota, Lancaster; June. New Jersey: Lakehurst, Morris, Ocean, 

 Warren; June, August. New York: Dutchess, Essex, Seneca, Tompkins; May, 

 July. North Carolina: Guilford; June. Ohio: Clifton, Delaware, Erie, 

 Franklin, Greene, Hocking, Pickaway, Ross; May, July. Oklahoma: Payne, 

 Sequoyah; July. Pennsylvania: Adams, Allegheny, Northampton, Phila- 

 delphia; May, July. Tennessee: Sevier; June. Texas: Bexar, Brazos, Brew- 

 ster, Dallas, Kerr, Madison, Val Verde; April, July. Virginia: Fairfax, Loudoun; 

 May, July. Washington, D.C: June. West Virginia: Greenbrier; July. 



Melanotus depressus is subject to considerable variation. Most 

 conspicuous is the range in overall size. The variation in elytron 

 length from 6.5-10.2 mm is about as large as any North American 

 Melanotus. There appears to exist a chne in the males with size of 

 the elytron diminishing to the west and south, as shown in the fol- 

 lowing chart. Curiously, the female does not appear to vary in 

 the same way. 



Variation in elytron length of M. depressus (average length in mm): 



Nonclinal variation exists in the size of the parantennal fovea and 

 mandibular pit. The pronotal punctures vary in size and density 

 but are almost always as large as those on the front, which are larger 

 than in morosus, and never as compact as in crihulosus. The sides of 

 the pronotum are usually markedly divergent and are a useful feature 

 in identifying the species when one is familiar with it. Few speci- 

 mens have the sides subparallel and lack the characteristic wedge 

 shape. 



Other than a broader than usual aedeagus seen in some northern 

 specimens, the male genitalia are constant. The female genitalia 

 also show little variation and are characteristic of the species. We 

 have found the genitalia to be reliable features of identification, and 

 dissected specunens can be identified positively with little difficulty. 



The bulk of specimens of the "americanus group" which we have 

 seen belong to either morosus or depressus. We have dissected a large 

 number of specmiens to verify our identifications. We concluded 

 that there are only two species in this section of the genus. We can 

 find nothing to support the recognition of the third species. The 

 type of parumpunctatus appears to us to be depressus, and it is within 



