6 MISC. PUBLICATION 6 9 8, U. S. DEPT. OF AGRICULTURE 



three segments forming a loose club, which is as long as or longer 

 than funicle, first two segments subtriangular, last segment oblong- 

 oval. Pronotum moderately convex, truncate at base and apex, with- 

 out gibbosities or dentiform tubercles, and without distinct lateral 

 margins; sides flattened or feebly concave. Scutellum (visible part) 

 quadrate or slightly transverse. Elytra moderately convex, with or 

 without longitudinal carinae on apical declivity. Legs long; anterior 

 tibia emarginate at base, strongly dentate on outer margin, with two 

 spines at apices, a large, arcuate one on inner margin and a short, 

 straight one on outer margin; tarsi 5-segmented, posterior pair as 

 long as or longer than tibiae, last segment of each shorter than the 

 preceding four segments united, second and third segments flattened 

 and expanded toward apices. Anterior and middle coxae separated. 

 Body elongate, cylindrical. 



Genotype. — Of Melalgias, Bostrichus femoralis Olivier. Of 

 Heterarthron, Bostrichus femoralis Olivier. (Designated by Guerin- 

 Meneville.) Of Exopioides, Exopioides carinatus Guerin-Meneville. 

 (Monobasic.) 



This genus contains 24 described species, most of which are found 

 in America, although a few species have been described from Asia. 

 The sexnal dimorphism of the species of this genus makes their study 

 very difficult. 



Melalgus Dejean (1835) is a valid genus based upon gonagra Fab- 

 ricius, with Bostrichus femoralis Olivier listed as its synonym, and 

 two undescribed species, chilensis Lacordaire and cylindricus Dejean. 

 Dejean (1836) included the same species under Melalgus, but also 

 placed Heterarthron Guerin (nomen nudum) as a synonym of that 

 genus; therefore Heterarthron Dejean attains validity by citation in 

 synonymy. Sturm (1843) placed Heterarthron as a synonym of 

 Melalgus Dejean. Since Guerin-Meneville (1844) has discussed the 

 two genera Melalgus and Heterarthron and has designated Bostrichus 

 femoralis Olivier as the genotype of Heterarthron, this species auto- 

 matically becomes the type of Melalgus (Article 30f of the Inter- 

 national Code). Guerin-Meneville (1844) erected Exopioides for 

 Exopioides carinatus, his new species from Bolivia. Lesne (1896) 

 placed Exopioides as a synonym of Heterarthron. Lacordaire (1857) 

 united Heterarthron and Polycaon, but Lesne (1925) in discussing 

 Van Dyke's remarks about granulatus connecting Polycaon and 

 Heterarthron, states that the form of the anterior feet and propleura 

 of the prothorax form good characters for separating the two genera. 



KEY TO THE SPECIES OF MELALGUS 



1. Antenna 11 -segmented; elytral declivity carinate at sides 2 



Antenna 10-segmented; elytral declivity not carinate at sides 3 



2. Marginal carina on elytral declivity short, extending to middle of declivity, 



the tip closer to lateral margin than sutural margin; punctures on 



elytra arranged in rows exesus (LeConte), p. 7. 



Marginal carina on elytral declivity long, extending nearly full length of de- 

 clivity, the tip (when viewed from above) midway between lateral and 

 sutural margins; punctures not arranged in rows-plicatus (LeConte), p. 7. 



3. Eyes separated on front (when viewed from front) by at least six times 



their own diameter; pronotum not distinctly wider than long; elytra 



granulose toward sides and apices confertus (LeConte), p. 9. 



Eyes separated on front by three times their own diameter; pronotum 

 distinctly wider than long; elytra not granulose toward sides or 

 apices megalops (Fall), p. 10. 



