NORTH AMKRIOAN COLF.Ol'TKRA. 83 



The illoiith Farts of COPKIS CAKOMXA: witli notes 

 on tlie homologies of the mandibles." 



BY JOHN B. SMITH, SC. D. 



Copris caroUna is the largest of our eastern Coprophagus Sca- 

 rab;x5idfe, and is not rare if the habits are known. It forms, for 

 some purposes, a good species for class work, and 1 made a rather 

 careful study of the mouth-parts, prelijuinary to its use for that pur- 

 pose. I cannot remember having seen a complete study of a similar 

 mouth, and the present paper may, therefore, contain some things 

 not generally known. 



The food of this insect is ft)und in the comparatively soft and 

 fresh excrement of cattle, and the sense of taste would seem rather 

 a useless one, not requiring excessive development of gustatory struc- 

 tures under the circumstances. Yet, the organs usually credited with 

 such functions are here well marked. The food being soft and pasty, 

 strongly developed mandibles are not needed, and, indeed, at first 

 sight they seem entirely absent. Our classification correctly says, 

 however, that they are present, and are pai'tly membraneous. 



In homologizing the head parts of an insect, the mandibles, max- 

 illa and labium, have each been called modified appendages to sepa- 

 rate segments, the head itself being made up of a number variously 

 estimated from four to seven. In most insects the maxilla is the most 

 complex organ and contains the largest number of distinct sclerites. 

 It is with this that we nuist compare other structures where either 

 division has not been carried so far, or where con.solidation has been 

 necessary. The labium is (piite usually a more or less completely 

 united organ with a single j)air of appendages, and in no form yet 

 known to me is the organ entirely divided or completely "paired." 

 All main jjarts of the maxilla have been identified in the labium, 

 and Prof. Comstock, in his "Introduction," has given an excellent 

 summary of the relation of the parts of each to the other. 



The mandibles are always separated or paired, and, though they 

 may be rudimentary or entirely wanting, I remember no case in 

 which they unite. That they are composed of more than one sclerite 

 is well known, and Kirby and Spence have named one of the pieces 

 the prostheca. Prof. Comstock also calls attention to this fact, and 



«■ This paper in its essential features was presented to Sectiou F, of the A. A 

 A. S., at the Washington meeting. Angnst, 1891, and charts i-ontaining enlarged 

 copies of tiie figures herewith given, were used to illustrate the paper. 



TRANS. AM. KNT. SOC. XIX. APRIL, 18}12. 



