INSECTA. 147 



INSEOTA, 



CANTHARIS.* Vesicating or blistering insects are those having the power, 

 when locally applied, of exciting that form of inflammation terminating in 

 a copious formation of serum under the cuticle. Very many species possess 

 this peculiar power, all belonging to the large Order called Coleoptera or 

 Beetles. The name ' fly,' as applied to them, is altogether a misnomer, flies 

 having but two wings and a suctorial mouth, while beetles, in addition to 

 their wings, have wing-cases or elytra and a masticatory mouth. 



CLASSIFICATION. 



The vesicants form by themselves a family in the great order of beetles, 

 and belong to that section characterized by heteromerous tarsi; that is, the 

 four anterior feet or tarsi are five-jointed and the posterior pair four- 

 jointed. 



From all other heteromerous beetles they maybe distinguished by the an- 

 terior coxal cavities being open behind and the coxae themselves prominent, 

 the head constricted behind, and the claws of the tarsi cleft or toothed. The 

 thorax at base is always narrower than the elytra. The family thus consti- 

 tuted is called MELOID^J, and is divided into two tribes, as follows : 



Side pieces of meso- and metathorax covered by elytra . MELOIXI. 

 Side pieces of meso- and metathorax not covered by elytra . LYTTINI. 



The first tribe contains five genera in our country, distinguished from 

 each other by the following characters : 



Elytra short, imbricated MELOE. 



Elytra not imbricated. 



Elytra shorter than abdomen. 



Elytra strongly divergent MEGBTRA. 



Elytra contiguous at basal fourth . . . NOMASPIS. 

 Elytra nearly or totally concealing abdomen above. 



Elytra connate, much inflated . . . CYSTEODEMUS. 



Elytra sub connate pubescent . . . . HENOUS. 



The insects of this tribe are all without wings, and will consequently never 

 be taken in flight. Species of Meloe are found in all parts of our country. 

 In early spring they occur under stones, while later in the season great num- 

 bers are frequently met with on certain favorite plants. They are all either 

 dull-black or bluish black, seldom with any lustre, and in many species the 

 males have the antennas distorted. Megetra is New Mexican. The two 



* Contributed by Dr. Geo. II. Horn. 



