NORTH AMERICAN COI.EOPTERA. 213 



The most important modification is in the number of joints, the 

 usual number is ten (fig. 4), while sixteen have O-jointed (fig. 11) 

 antenna}. This cliaracter must be used with extreme care, and in 

 no case sliould a species be said to have 9-jointed antenna* when but 

 one specimen is at hand. Instances ai'e by no means rare of speci- 

 mens of well known 10-jointed antennse species with but nine joints 

 and others will have the two antennce unequal in the numlier of 

 joints. It must not be foi'gotten that the tendency is toward a re- 

 duction of the number of joints by a coalescence and never to an 

 increase of the number, that is, the 10-jointed species have occasion- 

 ally individuals with 9-jointed antennse, but in no 9-joiuted species 

 has an individual ever been seen with ten joints. The coalescence 

 may go still further in the 9-jointed species, as specimens are before 

 me in which not more than eight joints can be counted. In one 

 species (ernob'^) all the males seen have 10-jointed antennae, while 

 the four females seen have them 9-jointed. 



Maxillary palpi. — The terminal joint varies in length between 

 the species as well as in its form, being either cylindrical and obtuse, 

 fusiform or ovate, often with a flattening or impression on the outer 

 side, but neither peculiarity seems to be confined to, or characteristic 

 of any group. 



Thorax. — This mend^er varies in form as will be seen by refer- 

 ence to the descriptions. In every case the form described is that 

 seen when viewed directly from above. Nearly all the species have 

 the lateral margin more or less ciliate, but the hairs are so apt to be 

 lost that no mention is made of them unless conspicuous. 



Elytra.— There is no great difference in the form or sculpture of 

 the elytra, except in crihrosa, in which the surface is subsulcate, the 

 intervals forming nine indistinct cost?e on each side. In the other 

 species the costse hardly deserve that name, except theoretically. 

 The sculpture consists of a well-marked sutural costa limited by a 

 deej) stria, although in several species this costa is absent (^ecodata 

 and politala). There are three oblique discal costse and one submar- 

 ginal parallel with the outer margin. The first costa, when distinct, 

 is dilated posteriorly, and is there limited internally by the sutural 

 stria. The other costie are scarcely distinct. The submarginal is 

 not often well defined. 



The extreme margin of the elytra is ciliate in very many of the 

 species, but the hairs are often lost by abrasion. 



