2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



It was on the recommendation of Mr. Lane that in 1955 the senior 

 author began a revision of North American Melanotus. Five years 

 ago he was joined by the junior author. During most of this time, 

 the work has been done during spare time by both. 



The new species were recognized early in the study by the senior 

 author and authorships are to be credited to him. 



We have arrived at the following conclusions concerning the tax- 

 onomy of the genus: the features distinguishing one species from the 

 other do not differ greatly; typical specimens of each species are 

 identifiable on the basis of external characters; some specimens of 

 each species vary enough to obscure the gap between the taxa; positive 

 identification can be made by the study of the genitalia, which is 

 specific in both sexes; and a natural division of the genus into sub- 

 generic taxa is not apparent to us at this time. 



One of the most striking features of the zoogeography of North 

 American Melanotus is that the species are concentrated east of the 

 100th meridian. Melanotus in North America is predominantly an 

 eastern genus (fig. 1). It is not within the scope of this paper to 

 dwell at length on possible causes of this distributional pattern, but 

 we may discuss it briefly. The apparent relationship of New and 

 Old World faunas suggests that there have been migrations over a 

 Bering Straits land bridge. We may further assume that the Mela- 

 notus click beetles which came from Eurasia and crossed the bridge 

 stayed on the eastern side of the Kocky Mountains. This might 

 have been the origin of the distributional pattern we see today. 

 Adaptation to the more humid climate and edaphic conditions pre- 

 vailing in the East may be responsible for the maintenance of the 

 pattern. 



In western North America there are only a few Melanotus and 

 most of these are in the Southwest. There appears to be a group of 

 species — longulus, hamatus, lanceatus, beameri, and concisus — which 

 are derived from a single ancestor. Perhaps it was an offshoot from 

 the main group in the East. At any rate, speciation has occurred 

 in the Southwest where we now find the five species, and one of these 

 has spread northward through the Great Basin and along the West 

 Coast to Canada. In the northern part of its range it has further 

 differentiated into a separate subspecies. 



The two most distinctive species of North American Melanotus also 

 are found in the Southwest. These are cribricoUis and chiricahuae, 

 and they are so distinct from others that we presume they are a 

 Neotropical element. 



The practical effect of these distributional patterns is that iden- 

 tification of Melanotus in the Far West is simple since there is only a 

 single species with two subspecies; in the Southwest there are only a 



