4 Natural History Bulletin. 



The $ of this insect was formerly described by Dr. Brendel 

 under the name Decarthron cornuttini^ and the ? as Bryaxis 

 inornata. Afterwards finding them in large numbers with 

 ants, he recognized them as sexes of one species. 



Plate IX, Fig. 74, 3; 75 ?• Habitat. Iowa. 



A second species of this genus was discovered by Mr. 

 Schwarz, in Florida, and is thus far unknown to me. It is 

 said to differ chiefly in the ankylosed antennal joints. 



Arthmius, Leconte. 



Head quadrate, differently sculptured in the sexes. Anten- 

 nas regular and straight in the $, irregular in the 3. Pro- 

 thorax globose. El3'tra much wider than long; abdomen 

 short. The line of juncticn of the ventral and abdominal seg- 

 ments is straight, not serrate as in Batrisus; first segment 

 one-third as long as wide, with four basal impressions, not 

 convex longitudinally but very much so laterally, margin 

 broad but not retuse. Fourth segment longer than its neigh- 

 bors, first ventral very long. Legs slender, the anterior in 

 the 5 dilated and armed with a strong tooth near the middle. 



A. GLOBicoLLis. Deep yellow. L-ength, 1.7 mm. 



Head, sides without the eyes parallel, occiput elevated, ver- 

 tex convex, two small foveas between the eyes, and two more 

 behind the frontal tubercles. T.'hese tubercles are oblique and 

 prominent, the frontal margin is transverse and emarginate in 

 the middle. A)itenn(s with every joint of a different form and 

 presenting a different appearance according to point from 

 which it is seen. First and second joint cyhndrical or obcon- 

 ical; third small, obconical, geniculate with the second; fourth 

 undefinable; fifth large, semi-spherical; sixth small and glob- 

 ular; seventh subglobular, truncate, very large; eighth trans- 

 verse, acute-ovate; ninth small, globular; tenth obovate; 

 eleventh large, acutely ovate. Prothorax globular, with a 

 straight flat transverse sulcus near the base, and at the base 

 is a linear slightly elevated margin. Elytra twice as wide as 



