ANDREMID.E. 281 



the habits of this genus, it is not even certain to what 

 genera it limits its visits. F. Smith records N. varia as the 

 parasite of Halidus cylindricus, N. soUdarjinis of 77. leu- 

 cozonius. Mr. R. C. L. Perkins has shown the difficulty 

 that would arise if this relationship were true, because, as 

 he points out, the ? Halidus lives through the winter iu 

 an impregnated state and does not store pollen till the 

 spring, so that these Nomndx, which appear in August, 

 would have no pollen on which to deposit their eggs. Either 

 they too must live through the winter in an impregnated 

 state, in which case they would appear again in the sjiring, 

 which is not the case, or there is an unknown peculiarity 

 about the habits of these Halictus iiiquiliues yet to be 

 discovered, or there has been some error in F. Smith's 

 observations — this last alternative seems to me the most 

 probable, as I have myself taken N. varia, which Smith 

 associates with Halidus cylindncus, with the autumn 

 brood of Andrena fulvicrus. All these questions add to 

 the fascination of this beautiful genus ; its species are 

 closely allied, and often difficult to separate; the chief 

 characters beyond colour, lie in the mandibles, the joints of 

 the antenna;, the spines of the apex of the tibife, and the 

 form of the apical segments of the abdomen in the S. The 

 various hosts where known, will be given under each 

 species. The genus is widely distributed over the northern 

 hemisphere, but F. Smith states that very few species aie 

 known from the southern ; the species are all more or less 

 fragrant, like those of Prosopis, I'sithijru>:, &c. 



(2) 1. Head ecarinate between the antenna3 . obtusifiions. 

 (1) 2. Head distinctly and sharply carinatcd 



between the antennte. 

 (34) 3. Labruin pale or with only sh'ghtly darker 



(tpots, species not very small. 

 (5) 4. Propodeum posteriorly bright and 



shining at the sides .... Eoberjeotia.va. 

 (1) 5. Proiiodeum posteriorly not bright and 



."hining at the sides. 

 (9) G. ScutcUum not raised, entirely llavous, 



