148 MEDICAL ZOOLOGY. 



known species have very rugose elytra, with a more or less irregular yellow 

 stripe ; otherwise they are black, with the head sometimes red. Nomaspis 

 occurs in Colorado; it resembles Meloe. Cysteodemus contains two species, 

 the most singular of the family. The elytra are much inflated and deeply 

 pitted ; in one species dull-blue, and in the other more brilliant in color. They 

 are found in the southern deserts of California and Arizona. One species at 

 least is excessively abundant, and possesses moderate power as a vesicant. 

 Henous occurs on our western plains and in Texas. It is deep black in 

 color, and the only pubescent species in the group. 



The second tribe of the family, Lyttini, contains by far the greater num- 

 ber of species and genera, the latter numbering already sixteen in our 

 own country, divided into three sub-tribes. 



Front of head not prolonged below insertion of antennae . HORIINI. 

 Front prolonged, frontal suture evident. 



Mandibles prolonged, acute . . . . NEMOGXATHINI. 



Mandibles obtuse, short LYTTINI. 



The first sub-tribe contains rare species, the one found in the eastern re- 

 gions is black with red wing-cases, and though destitute of wings, has been 

 seen flying by means of tlae elytra alone. All belong to the genus Tricrania. 

 The Nemognathini are divided into three genera : 



Maxillae with the outer lobe prolonged. 



Antennae not thickened externally .... NEMOGNATHA. 



Antennae thicker towards tip, thorax conical . . GNATHIUM. 

 Maxillae with the outer lobe not prolonged . . . ZONITIS. 



The prolongation of the maxillae, in the first two genera, is a curious char- 

 acter, and enables the insect to obtain its food from the flowers on which it 

 lives in the same manner as bees and suctorial insects generally. These in- 

 sects are for the most part western, occurring abundantly on the plains and 

 in California on flowering plants. The sub-tribe, Lyttini, contains twelve 

 genera, divided into four groups : 



Vertex not elevated. 



Second joint of antennae long .... MACROBASES. 



Second joint of antennae much shorter than third . LYTTVE. 

 Yertex elevated. 



Antennae filiform, of moderate length . . . EUPOMPH.E. 



Antennae very short, not longer than head . . PHODAG^E. 



The group Macrobases contains two genera, Macrobasis with wings, and 

 Apterospasta without. They contain some of our largest species. The third 

 and fourth groups contain each one genus and species, and are of such 

 rarity as never to have been experimented with. They are found in Arizona 

 and California in desert regions. The Lytta3 are more numerous, and form 

 eight genera : 



