HALICTUS. 217 



burrow solitarily and apart from their congeners. In 

 burrowing they form a tunnel which branches off to 

 several cells, the excavations being as inartificial as are 

 those of Andrena. Walkenaer tells us in his memoir 

 upon the genus Halictus, that they line their cells with 

 a kind of glaze, that they burrow in horizontal surfaces 

 to a depth of about five inches, and which they polish 

 very smoothly previous to covering it with their viscous 

 secretion, and that the cells are all oval, the largest end 

 being at the bottom. He says also that they burrow 

 solely during the night, especially when the moon is 

 shining, when it is difficult to walk without treading 

 upon them ; so numerous are they, indeed, that they 

 look like a cloud floating close to the surface of the 

 ground. Although burrowing thus at night, it is only 

 during the day that they supply their nests with their 

 provision of pollen and lay their eggs. Each of their 

 cells is furnished with a small ball of pollen, varying in 

 size with the species, but which never entirely fills the 

 cell, and is affixed intermediately between both extremi- 

 ties, and upon the mass contained in each cell they de- 

 posit their small egg, which is placed at the extremity 

 of the lump of pollen most distant from the entrance. 

 The larva is hatched in about ten days, when it changes 

 into the pupa. Some doubt attaches as to the length of 

 time that the pupa remains before its transformation 

 into the imago, and also as to the period at which this 

 takes place. A peculiarity attends the appearance of 

 the larger species. Some are very early spring insects, 

 among which is the Halictus rubicundus ; this I have 

 seen in abundance on the first fine spring days collecting 

 its stores on the flowers of the chickweed. It is then in 

 the very finest condition, and it is really a very beautiful 



