10 COLEOPTERA OF NORTH AMERICA. 



Lec. Both of these species are from Lake Superior. Syntomium 

 is represented in Russian America. The other genera are found 

 on both sides of the continent. 



Tribe VII.— OMALIIVI. 



In this tribe the prothoracic spiracles are concealed by the 

 inflexed portion of the pronotum; the presternum behind the 

 coxae is membranous ; the anterior coxa? are conical and promi- 

 nent, the posterior ones transverse ; the hind trochanters are on 

 the internal margin of the thighs; the tarsi are 5-jointed; the 

 palpi are filiform, except in Coryphium, where they are subulate ; 

 the head is furnished behind with two simple lenses or ocelli, 

 which are usually placed on a line joining the posterior margins 

 of the eyes. The antenna? are inserted under the lateral margins 

 of the front. The second ventral segment is carinate at the base. 



The genera are numerous, and are best distinguished by the 

 parts of the mouth, which are not to be examined without dis- 

 section. For a full account of the differences between the genera 

 the student must refer to the second volume of the Insecten 

 Deutschlands, by Kraatz. The following characters may enable 

 him to recognize those of our fauna : — 



A. Maxillary palpi with the last joint long or moderate ; posterior tarsi with 



joints 1 — 4 of unequal length ; elytra moderate ; 

 Mandibles toothed ; tibiae not spinous ; hind tarsi with the first joint 

 elongated ; 



Maxillary palpi with the last joint not elongated. Anthophagus. 



Maxillary palpi with the last joint three times as long as the pre- 

 ceding. Lesteva. 

 Mandibles not toothed ; 



Tibiae spinous ; hind tarsi with the first joint elongated. Acidota. 



Tibiae not spinous ; hind tarsi with the first and second joints equal ; 

 Lobes of the maxillae elongate, corneous. Olophrum. 



Lobes of the maxillae membranous. LathrimjEtim. 



Tibiae spinous ; hind tarsi with the first and second joints elongated, 

 not equal, first very long. Amphichroum. 



Tibiae not spinous ; hind tarsi with the first joint slightly elongated ; 

 one mandible toothed. Porrhodites. 



B. Maxillary palpi with the last joint small, subulate. Coryphium. 



C. Maxillary palpi with the last joint long ; hind tarsi with the joints 1 — 4 



short, equal ; 



Tibiae very finely spinous ; elytra long. Omalipm. 



Tibiae not spinous ; elytra long. Anthobium. 



Elytra very short. Micralymjia. 



