92 Journal New York Entomological Society. [Voi. xxi. 



or the lack of them, the character of the punctuation and the form 

 and sculpture of the metasternum is left out, and no comparative 

 notes are given. Unfortunately I have not been able to see his types. 



The structural characters most useful in separating the species 

 are the form and markings, such as depressions, margins, etc., of the 

 prosternal process, metasternum and coxal plates as well as the shape 

 and structure of the parts of the upper surface of the body. In fact 

 the structure of the under body seems to vary very little among in- 

 dividuals of a species, which fact was not at all appreciated by Mr. 

 Crotch, as shown in his " Review," and little made use of by Dr, 

 Leconte. 



If the mid-metasternum of a species is margined, and that margin 

 extends backwards so as to reach, or approximate, the anterior suture 

 of the antecoxal piece and in another species the margin does not 

 reach more than half way to the suture, the two species could be al- 

 most certainly separated by a reference to that one character alone. 

 So also can the shape of the coxal plates, whether rounded or angu- 

 late, be used with confidence. 



Punctuation, both on the upper and under surfaces, especially as 

 to whether the punctures are large and shallow, or small and deep, 

 is quite characteristic and constant. 



The study of large series of specimens of species easily recog- 

 nized from some decided structural character has led me to value 

 maculation rather highly as an aid in determining species. While 

 spots may be dilated, sometimes even to the point of coalescence, or 

 lines lengthened, or either of them diminished almost to obliteration, 

 the character of the color markings, that is whether lines or spots, or 

 even the pattern, will usually be indicated. 



I do not mean to imply that some species do not mimic others 

 rather closely in pattern of maculation, but in that case, when struc- 

 tural differences are found, some modification of the markings will 

 be observed which, while perhaps slight, will be found constant. 



Variation in color markings along the above lines is not at all un- 

 common in the species of Haliplus, but in Peltodytes the maculation 

 is remarkably constant and may be almost absolutely relied upon, as 

 also may the color of the hind femora. 



In the latter genus if one specimen has seven spots on each elytron 

 and another six, or if one has a sub-humeral spot and another has 



