side along the whole of the organ. In other cases, where the antennæ are not remarkably longer in the male they have extra development by becoming thicker, as in _Melecta_; and in _Megachile_ the terminal joint of their antennæ is laterally dilated and compressed. In scarcely any case are they geniculated at the scape in the male, as they are in the female. The other genera with clavate antennæ have the same structure in both sexes, as in _Panurgus_ and _Ceratina_. Remarkable peculiarities in the terminal ventral segment or segments of the male may be found most conspicuously developed in _Halictus_, _Cœlioxys_, _Anthidium_, _Chelostoma_, _Heriades_, _Osmia_, _Apathus_, Bombus, and Apis. In _Cœlioxys_ and _Anthidium_, and some of the _Osmiæ_, this sex is further furnished with a series of projecting spines, processes, or serrations at the apex of the terminal dorsal segment. In _Chelostoma_, the ventral structure of the male is very singular, the apex being adapted to a mucro at the base which permits the insect to curl up this portion of the body similarly to its antennæ, the furcated extremity of the abdomen fitting, when thus folded, upon the mucro. It is as well to draw observation to these peculiarities, which give additional interest to the study of the group. The genus _Eucera_ appears in May and June. In some parts they are found in large colonies; although I have seen them abundant I never found them in this gregarious condition, and I have usually discovered them frequenting loamy and sandy soils; they burrow a cell six or eight inches deep, form an oval chamber at its extremity, which as well as the sides of the cylinder leading to it they make extremely smooth, and by some process prevent its absorbing the mixture of honey and pollen which they store for the supply of the larva, and each contains but one young one. These, having full fed, lie in a dormant state throughout the winter and do not change into pupæ until mid-spring, and speedily transform into the imago, which, until fully matured, is closely in every part and limb covered with a thin silky pellicle, wherein it lies as in a shroud, but at its appointed time, regulated by some influence of which we have no cognizance, active life becomes developed, it then casts off its envelope and comes forth to revel in the sunshine, in close companionship with a partner which its instinct promptly teaches it to find. The largest of our native _Nomadæ_ is its parasite the _N. sexcincta_, and which seems wholly restricted to it, but which is often even rare in places where the _Eucera_ abounds. The female, like those of the rest of the bees, is no time-waster, but flies steadily to and fro in her occupation of provisioning her nest, and the male often accompanies her in these expeditions, gallantly winging about with extreme velocity as if to divert his sedulous companion in the fatigue of her toil, by his evolutions and his music, which is very sonorous.