Et'CERA. 233 



Halictus, Andrena, Daxypoda, Panurgus, Saropoda, 

 Ceratina, Calioxys, Chelostoma, Heriades, Anthocopa, 

 and Apathus; of the second class we have Prosopis, 

 Sphecodes, Macropis, Anthophora, Nomada, Melecta, 

 perhaps Epeolus, according to Latreille's idea, Stelis, 

 Anthidium, Osmia, and Bombus ; the third class com- 

 prises in our series merely Cilissa, and in this series the 

 male characteristics that have suggested the name are 

 just as few, being limited to the present genus. But 

 the males among the bees exhibit in many cases strong 

 and striking peculiarities which distinguish them from 

 their partners. Exclusively of the general distinction 

 expressed in their organic difference by the possession 

 of one additional joint to the antennae and one more 

 segment to the abdomen than is exhibited in the fe- 

 males, we find in many cases in these two parts of their 

 structure very marked singularities. Great sexual dif- 

 ferences in the length of the antennse are not restricted 

 to the present genus ; in fact, in most of the genera, 

 this is the first striking feature, but which becomes 

 conspicuously so in some species of Sphecodes, in most 

 of the Halicti, in some Nomada, in Chelostoma, Osmia, 

 Apathus, and Bombus. In Eucera and Sphecodes, each 

 joint of the flagellum- is slightly curved, and in the 

 former the surface of those joints appears compounded 

 of hexagons. In Chelostoma the antennae, besides being 

 longer than in the female, are also very much slighter 

 and slightly compressed, and have a structure capable 

 of curling upon itself; in the female of this genus the 

 organ is clavate; and in Osmia, besides their length, in 

 one species the male has a fringe of hair attached to 

 one side along the whole of the organ. In other cases, 

 where the antennae are not remarkably longer in the 



