23,6 Schultze: Pachyrrhynchus 615 



ovate, not strongly inflated, and somewhat depressed dorsally. 

 The greatest diversity of body forms, particularly of such parts 

 as the rostrum and the elytra, are found in species of Metapo- 

 cyrtus. In most of the species of that genus secondary sexual 

 characters are very pronouncedly manifest, mainly in the dif- 

 ferently shaped elytra, in some species in a truly remarkable 

 degree. In species of Homalocyrtus the form of the elytra of 

 the two sexes is also very much differentiated. In the males 

 the elytra are mostly divergent toward the apex, in the female 

 more uniformly oblong-ovate. Some time ago I carried out 

 some comparative studies on the penis structures 5 of a large 

 number of species of different genera of the group. The follow- 

 ing were examined: 



Pachyrrhynchus 27 



Metapocyrtus 3 



Pantorhytes 1 



Psetidapocyrtus 2 



Apocyrtus 1 



Homalocyrtus 3 



Macrocyrtus 2 



The studies showed very clearly, with particular reference 

 to species of the genus Pachyrrhynchus, that this organ is a 

 hard chitinous tube of variable length and form, according to 

 the species, the color pale translucent brown to dark chestnut 

 brown or black. In general aspect the penis forms, with refer- 

 ence to generic characteristics, exhibit marked differences. 



Concerning the value of this organ as a medium for the deter- 

 mination of a species, I consider it an excellent criterion, since 

 I found it to be uniform in shape in as many as ten specimens 

 of a species that I examined in this respect. Furthermore, a 

 rather great diversity of form of this organ is found among 

 the different species of a given genus. In generic differences 

 in the structure of this organ certain species of Pachyrrhynchus 

 appear closest in similarity to species of Pantorhytes and Meta- 

 pocyrtus; but all three of these genera are in great contrast m 

 this respect to species of the genera Macrocyrtus, Pseudapo- 

 cyrtus, Apocyrtus, and Homalocyrtus. In order to demonstrate 

 the specific characteristics of the penis structure and the value 

 of this organ as a medium for identification among different 

 species of the genus Pachyrrhynchus, figures of 26 species are 

 given. (Plate 3, figs. 13-38.) 



5 Philip. Journ. Sci. 21 (1922) 592, pis. 3 and 4. 



