4 GEO. H. HORN, M. D. 



The tarsi in the vast majority of species are short, usually not 

 longer than one-third the tibiae and moderately dilated. In two 

 species however they are long and slender, equalling at least the half 

 of the tibiae and not dilated. The claws exhibit feeble variations, not 

 of sufficient moment however to mention. 



The antennae show a modification in but one species. The normal 

 form is that in which the fifth joint is suddenly broader than the 

 fourth and the following joints similar to it. In gemina however the 

 fourth joint is a little wider than the third and the fifth a little wider 

 than the fourth so that the abrupt dilatation of the fifth joint entirely 

 disappears. 



The surface of the body has usually a more or less distinct tinge of 

 bronze and from the minute punctures of the intervals arise usually 

 brownish hairs. Four species, subbalteata, culta, quadriviltata and 

 r/emina, have short erect setge. 



Regarding the ornamentation nothing can be said in general. The 

 accompanying plate will show the styles. There is but one color 

 character of value, the presence of the yellow side spot on the thorax, 

 it is either constantly present in a given species or as persistently 

 absent. 



Based on the characters above mentioned it is proposed to divide 

 the genus into several groups in the following manner : 



Tarsi short, moderately dilated 1. 



Tarsi loDg, equalling more than half the length of the tibite 2. 



1- — Presternum with the anterior margin trisinuate, (PI. I, A). 



Acmseoderse sinuatae. 

 Prosternum simply shorter than the anterior angles, (PI. I, B). 



Acmaeoderse emarginatse. 

 Prosternum truncate, as long as the anterior angles, (PI. I, C). 



Acmaeoderae truncatse. 

 Prosternum lobed at middle, alse attaining the angles, (PL I, D). 



Acmaeoderae lobatae. 

 2. — Form slender, prosternum lobed or truncate Acmaeoderae graciliformes. 



AcM^ODERyE SINUATE. 



This group is composed entirely of species of at least moderate 

 size and those also in which the thorax attains its greatest width and 

 depression and the most distinctly reflexed margin. Doubtless very 

 many Mexican species go here. In our fauna it is at present the 

 largest group the species being thirteen in number and arrange them- 

 selves naturally in the following manner : 



